LECTURES ON SCIENCE
AND NATURALISM
by
John Shook, PhD, Center for Inquiry and the University at Buffalo
Contents
Lecture
One: Scientific Method
Lecture
Two: Scientific Realism
Lecture
Three: Naturalism is superior to Supernaturalism
Lecture
Four: Varieties of Naturalism
Lecture One:
Scientific Method
Scientific
Method is used to construct scientific knowledge about nature. Knowledge is
increased through careful observation and logical inference. Observation,
inference, and knowledge are almost always fused together to some degree.
For example, much of our observation of the world is recognition of the
familiar, which is observation informed by knowledge. Also, most of our
observations of objects in the world are informed by inference, because the
information from our senses in quite superficial by itself. Using vision, we
only really see surfaces, shadows, colors, patterns: but we observe objects
having depth and volume and texture. Using hearing, the various noise we hear
become the sounds of things near and far, like approaching cars or hidden
animals. Our ordinary everyday experience of the world is a type of knowledge,
which we can characterize as practical reliable knowledge. Although this
knowledge of ordinary experience is often mistaken, it works well enough for
our daily activities. Examples are gathering vegetables and cooking them for a
nutritious meal, or weaving cloth and sewing it to make clothing.
Empiricism and Rationalism
Philosophers
who believe that experience is the source and ultimate justification for all
knowledge are called empiricists. Some empiricists have looked to experience to
provide a higher type of knowledge than practical reliable knowledge, a type of
knowledge that is infallible and certain, which will never turn out to be false.
But not all empiricists search for certain, perfect knowledge -- we might call
those who do undertake this search "extreme empiricists". There have
been few extreme empiricists, since there are serious problems with trying to
find reasonable cases of experiences that give perfect knowledge about the
world. These problems are so severe that other rival philosophers have
concluded that experience by itself cannot be a source of perfect knowledge at
all. Indeed, most empiricists do accept that experience needs help from reason
to establish knowledge about the world. However, experience (even with help
from reason), can never establish perfect knowledge about the world (as will be
explained below).
A
philosopher searching for perfect knowledge will conclude that experience
cannot play any role in perfect knowledge. What other source of perfect
knowledge is possible? The alternative to experience is reason, and
philosophers who emphasize the large role that reason must have for knowledge
are called rationalists. Some rationalists, searching for perfect knowledge,
will use only reason to find knowledge, and we might call them "extreme
rationalists". As it turns out (also to be explained below), reason by
itself cannot establish any perfect knowledge about the world. That is why
there have been few extreme rationalists in the history of philosophy. Most
empiricists have decided that experience needs a little help from reason to
establish knowledge, and most rationalists have concluded that reason needs a
little help from experience to establish knowledge about the world. Debates
between these empiricists and rationalists are surveyed by this article about "Rationalism
vs. Empiricism". If both sides assume that perfect knowledge must be
the quest, then both sides must fail. Experience and reason can indeed be
artificially separated from each other, in the philosophical imagination
(again, far from our ordinary experience in which observation, inference, and
knowledge are partially fused together). By artificially separating experience
from reason, extreme empiricists and extreme rationalists actually destroy the
possibility of knowledge about the world. That is why most philosophers
conclude that both experience and reason are needed for knowledge about the
world, and the difference between empiricists and rationalists comes down to
different estimates about how much experience and reason contributes to
knowledge.
In the
extreme empiricists' philosophical imagination, experience is
"purified" of anything that might admit the possibility of error and
illusion, and the empiricists announce the discovery of a realm of
"sensations" or "sense data" that can never prove false.
Example: "There is a bright point of light." In this example, a
person making this judgment is claiming to observe something and describe it so
narrowly that she can never be shown to be wrong. If instead she claimed,
"There is a star in the sky", this judgment could conceivably turn
out to be wrong, because we can imagine how further investigation could show
that what this person really experienced was not a star (but instead a planet,
or an airplane, etc.). The problem with pure sensations, even when described in
infallible ways, is that they cannot help establish knowledge about the
world. Knowledge consists at least of judgments about the world expressed
in propositions of some public language. If pure sensations are expressed in
judgments, they either (1) fail to be about the world, and instead are about
some realm of pure experience (just lights and colors and noises and tastes,
etc.); or (2) they try to be about the world but begin to suffer from the
possibility of error and illusion (e.g. is that really a circle of light, or
maybe an ellipse -- and is it red, or reddish-orange? etc.). Furthermore,
anything like scientific knowledge about the world would at minimum consist of
judgments about the regular behavior of objects and events in the world. Yet
pure experience cannot establish these sorts of judgments because of the "Problem of
Induction": even though a series of experiences may have common
features, and appear to present a pattern, it is impossible to have perfect
knowledge that this pattern would continue into the future. Empiricism's quest
for perfect knowledge through experience alone can therefore only lead away
from knowledge about the world and can never produce anything like scientific
knowledge. In the 20th century, scientific anti-realists have generally
preferred types of Empiricism
(like positivism's
view that science can only describe patterns of phenomena).
On the
other side, in the extreme rationalists' philosophical imagination, reason must
have a method of inference for establishing perfect knowledge. The only method
of inference that promises to prevent all possibility of error is deduction.
Deduction is a careful relation between premises and a conclusion, designed so
that if you know that the premises are all true, you can also know that the
conclusion is true. So long as the premises remain true, the conclusion can never
turn out to be false, and your knowledge of the conclusion is perfect
knowledge. You can read an advanced article about "Classical
Logic" here. The difficulty with deduction is that a person's perfect
knowledge of conclusions depends on perfect knowledge of the premises. How can
a person perfectly know the premises? Well, perhaps other deductive arguments
show that each of the premises are knowably true. Ok,
but those additional arguments must have their own additional premises, which
all need their own deductive arguments to justify why they can be known to be
true, and so forth, and so on -- are an infinite number of arguments needed for
any knowledge? That seems strange, since no person could hold an infinite
number of arguments in their mind, and thus can never be assured that perfect
knowledge is achieved.
There are
two other alternatives: (1) perhaps some premises can be known to be true
without any argument (see "Foundationalist Theories of Epistemic Justification"),
or (2) perhaps some special conclusions can serve as premises for other
arguments, which in turn prove conclusions that serve as premises justifying those
special conclusions, so that only a finite number of arguments are
actually needed (see "Coherentist Theories of Epistemic Justification").
Rationalists have usefully developed the foundationalist
or coherentist alternatives, and these developments
are very important for scientific method and realism, so they will be discussed
further in sections below. However, extreme rationalism is a dead-end because
pure deductive inference (nor inductive or abductive inference either -- more
about these below) cannot establish any perfect knowledge about the world.
Reason by itself can form perfectly coherent systems of thought, but there is
no way to determine which system must be true, and most are quite compatible
with the natural world. In other words, pure reason's truths are either (1) not
about the natural world at all, or (2) somehow they are true about all possible
worlds. Most rationalists therefore admit that reason needs some information from
experience in order to produce knowledge about the actual natural world (thus
agreeing with most empiricists that experience needs some assistance from
reason).
The
endless debates between extreme empiricism and extreme rationalism are
inconclusive, because each side can show why the other side must be inadequate.
Experience by itself cannot be a path to perfect knowledge about the world, but
reason alone cannot establish any knowledge about the world either. Most
philosophers turn away from this fruitless debate and take a compromise
position that could be called "Rational Empiricism": knowledge about
the world is created by experience and reason working closely together.
However, rational empiricism is a philosophical position that admits that
perfect knowledge about the world is never possible. There may be types of
perfect knowledge, but none of them can be about the actual natural world.
Since scientific knowledge is about the natural world, then scientific
knowledge cannot ever reach perfect knowledge, and therefore any scientific
knowledge is less than certain -- instead, scientific knowledge, even at its
best, is always fallible (could be exposed as false in the future) and
revisable (could be improved or entirely replaced with better scientific knowledge).
The scientific method itself is not a case of perfect knowledge either --
rather, scientific method is a tool that can be (and has been) modified and
improved through regular use and testing. Furthermore, although there is
general scientific method that is explained here, each of the sciences uses its
own specific version of the scientific method that works best for that science.
Scientific Observation
We can now
ask this question: what is the relationship between the knowledge of ordinary
everyday experience and scientific knowledge? Is scientific knowledge a quite
different sort of knowledge from ordinary reliable knowledge? This introduction
to scientific method takes the position that scientific knowledge is also a
kind of reliable practical knowledge, but vastly improved: the reliability and
practicality of scientific knowledge is far greater than that of ordinary
everyday knowledge. Also, the scientific method depends on ordinary experience,
but often must improve that experience for its own purposes to become
scientific observation.
A person
makes a scientific observation by properly using an approved instrument
(one that has the confidence of the scientific community) for focus and/or
measurement to carefully experience a thing or event that is public
(could be observed by others too), and the person makes a record of the
observation using a description that is precise (the thing or event is
described in a more formal way than ordinary language, using special concepts
and categories to increase discrimination and accuracy). The best kinds of
scientific observations are designed to be both precise and public: these
observations are described using concepts and categories specially designed and
used by a scientific community of people, all trained for making good
observations. Example: Measuring the movement of a planet across the sky from
night to night across two years' time. The astronomy community designed a
system of concepts and categories (right ascension and declination) for
describing the exact position of any object in the sky. Using this system, any
trained and careful observer will be able to accurately record the position of
a sky object.
When a
community of scientists all use the same system for observation, and are
well-trained to perform observations using this system, the community has
established the possibility of scientific objectivity: scientific
knowledge about natural objects and events within experience. This scientific
objectivity, which provides reliable and practical information about objects
and events, is the starting-point of scientific method and makes science
possible. The scientific method uses experience to produce knowledge, but not
just any sort of experience: only scientific observation counts. Of course, scientific
observation is still fallible and revisable, since scientists make errors and
misjudgments even when sincerely trying to do their best. The best kind of
scientific observation is highly objective by being repeatable and durable:
lots of scientists have been able to make the same observation (or almost the
same, within a reasonable amount of error) over long periods of time.
Observation,
inference, and knowledge are always fused together to some degree. This is true
for ordinary experience, and it is true for scientific observation. For
example, when astronomer Tycho Brahe observed and
recorded the positions of the planet Mars during the late 1500s,
he used a telescope. Brahe's observations enjoyed a high level of scientific
objectivity because of their precision and replicability,
which was only possible by using his excellent telescope. Only an instrument
already approved by a scientific community, which agrees on how that instrument
is correctly used, can be used to make scientific observations. The scientific
community endorsed the use of the telescope because by that time, scientists
understood how telescopes work and they trusted well-made telescopes to
accurately magnify the visual image of the object viewed. Scientists had
reliable and practical knowledge about telescopes, and they also had by that
time a well-established theory about how a telescope worked, from the science
of light and optics. In summary, Brahe was able to make scientific observations
of Mars because his experience was enhanced by inferences from what he saw
through the telescope to make conclusions about the position of Mars in the
sky, and these inferences depended on his knowledge about the telescope.
A
scientist's own senses can qualify as scientific instruments. For example, a
scientist's own eyes can be adequate instruments for making scientific
observations. Unless Brahe's eyes were adequate instruments for looking through
the telescope properly, his observations would not have been accepted as
scientific by the community of scientists. The trained eyes of a botanist are
used to make scientific observations about the structures of flowers. The
trained ears of a ornithologist are used to make scientific observations of
bird calls, as another example.
There are
three types of logical inference: deduction, induction, and abduction.
Deduction: If the
two premises are both true, then the conclusion must necessarily be true.
Conversely, if the conclusion is false, then one or both of the premises must
also be false. Deduction is the only method of inference that is capable of
proving that a proposition is true. You can consult this article on "Deductive
Reasoning" and another on "Logical
Consequence".
|
All the
beans from this bag are white. |
A fault
line causes earthquakes. |
A force
exerted by the sun will keep its planets in orbit. |
Induction: The two
premises describe the qualities of a sample from a larger group, which suggests
a pattern. The conclusion states that the pattern will continue. If the two
premises are both true, then the conclusion has some (perhaps small)
probability of being true (somewhere between 0% and 100% probability). The
degree of probability depends on the size of the sample, the size of the larger
group, and the method used to select the sample. You can consult this article
on "Statistics"
and another on "Induction".
Induction can never prove that a proposition is true. That is because it is
always conceivable that a pattern will change or stop at some point in the
future: this is the "Problem of
Induction". Although induction cannot lead to truth, it remains very
useful so long as it is done carefully to avoid "Faulty
Generalization".
|
These
beans are from this bag. |
There is
a fault line near Boise. |
The sun
exerts a force of gravity on its orbiting planets. |
Abduction: The two
premises state what is known now about a situation. The conclusion is a
hypothesis about how that observed situation came to be that way -- a
hypothesis that tries to explain the current situation in terms of some other
hidden situation that hasn't been observed. An abductive inference has this
form:
If P, then Q.
Q.
Therefore, P.
Because
abductive inference has this logical form, this inference commits the logical
fallacy of "Affirming
the Consequent" and it is always invalid. No abductive inference ever
gives sufficient reason to believe that its conclusion is true. Because there
are always potentially conceivable alternatives for why Q is true (for example,
maybe it is also true that If R, then Q -- so maybe R is true instead), there
is never good reason to believe that P is true just because Q is true. You can
read this article on "Abductive
Reasoning".
|
All the
beans from this bag are white. |
A fault
line causes earthquakes. |
A force
exerted by the sun will keep its planets in orbit. |
Understanding
abduction is essential to the scientific method. Abduction
is science's only way of suggesting novel explanations for the observable
events and things in nature. Deductions do not give explanations: their
conclusions only restate, in a rearanged way, what is
already stated by the premises. Inductions do not give explanations: their
conclusions only make predictions about the future. Abductions do give
explanations: their conclusions are statements about things or events that have
not yet been observed, or will never be observed, which are responsible for the
facts stated in the premises. In the first example about the beans, the two
premises state what is known now: all the beans from this bag are white, and
these beans are white. What might explain where these white beans came from?
Well, they might have come from that bag, where all the beans are white too. If
these beans really did come from that bag (an event that was not observed by
the person making the abductive inference), that would explain where the beans
came from. In the second example about the sun and gravity, the two premises
state what is known now: a force exerted by the sun will keep its planets in
orbit, and planets are in orbit around the sun. What might explain why these
planets go in orbit around the sun? Well, the first premise states that if
there was a force exerted by the sun then the sun will keep its planets in
orbit. What force could be exerted by the sun? Well, a force of gravity, if it
really existed (but it has not been observed), would explain how the sun could
exert a force on its planets. If there really was a force of gravity exerted by
the sun, that would explain how the sun keeps its planet in orbit.
A
scientific explanation in general has the following abductive form: These facts
are known to be the case now; if some presently hidden thing really exists or
did exist, then the known facts would have to be true; therefore, some
presently hidden thing really exists or did exist.
There are
four basic types of hidden things or events (hereafter collectively called
"entities") that play roles in explanations by science. Let us call
them Type I entities, Type II entities, Type III entities, and Type IV
entities.
Type I. An
entity which could be observed directly. Example: Did these white beans come
from that bag? -- Well, the explanation is "hidden" in the past.
Perhaps someone observed where those beans came from. When a Type I entity is
hypothesized by an abduction, that hypothesis can still be proven to be true by
actually directly observing it.
Type II.
An entity which could be observed instrumentally. Example: Did a fault line
cause that earthquake? -- Well, the explanation is "hidden" under the
ground. Perhaps someone can instrumentally observe the fault line using
seismology equipment. When a Type II entity is hypothesized by an abduction,
that hypothesis can still be proven to be true by actually instrumentally
observing it.
Type III.
An entity which could be observed by some new instrument not yet invented.
Example: Did the very early universe have a certain structure? -- Well, we now
have no instrument that can make any good observations of the very early
universe. Perhaps someone will invent a far more powerful telescope. After the
invention of the needed instrument, the Type III entity changes to a Type II
entity. When a Type III entity is hypothesized by an abduction, that hypothesis
can never be proven to be true, until the needed new instrument is invented.
Type IV.
An entity which cannot be identified by any direct or instrumental observation.
Examples of such non-observable entities are black holes, the force of gravity,
and the curvature of space-time. Observed evidence for such entities must
always consist of the detection of their effects on scientific instruments.
Sometimes science advances through both a theoretical and instrumental
advancement, so a Type IV entity can be converted into a Type III or Type II
entity. For example, until the 20th century, science had to classify atoms as
Type IV entities, but now large atoms can be instrumentally observed. When a
Type IV entity is hypothesized by an abduction, that hypothesis can never be
proven to be true, and it is never reasonable to believe with 100% certainty
that this entity really exists.
The
Scientific Method has three stages and six steps. In the
first stage, the "observation stage", there are two steps which
describe how science begins with scientific observation and then uses induction
to formulate a law of nature. In the second stage, the "hypothesis
stage", there are two steps which describe how science uses abduction to
postulate one or more hypothetical entities (from among the four Types I-IV) to
explain what has been observed in stage one. In the third stage, the "testing
stage", there are two steps which describe how science uses deduction to
test the hypothesis from stage two against more scientific observations and
against rival hypotheses.
Stage One:
Observation
Step One: Phenomena.
Using established scientific knowledge, new scientific observations of a
pattern of events are recorded.
Step Two: Natural
Law. Using induction, this pattern of events is believed to continue into
the future, and this pattern can usually be expressed as a law of nature
(sometimes as an equation, for example).
Stage Two:
Hypothesis
Step
Three: Explanation. Using abduction, a hidden entity of Type I, II, III,
or IV is postulated as the explanation for the law of nature found in step two.
Step Four:
Prediction. For a Type I or Type II entity: its predicted existence can
be tested by direct or instrumental observation.
For a Type III or Type IV entity: using deduction the actual existence of this
hidden entity implies that it must be responsible for other unexpected patterns
of events also, besides those observed in step two and other patterns already
recognized by science. These other unexpected patterns are the hypothesis's
predictions. To be optimally useful, a prediction should be very unexpected
(ideally, forbidden by a rival hypothesis); very specific (vague predictions
are suspicious because they are too easily confirmed); and not very difficult
to test by experiment in the next stage.
Stage
Three: Testing
Step Five:
Experiment. For a Type I or Type II entity: its predicted existence can
be tested by scientific observation, so the needed observations are attempted.
For a Type III or Type IV entity: using established scientific knowledge and
deduction, experiments are designed and conducted to find out whether any of
the predicted patterns of events from step four can be scientifically observed.
Step Six: Verification,
Confirmation, or Falsification. For a Type I or Type II entity: if its
existence is looked for and successfully verified by scientific observation,
then the hypothesis is verified as true (although there may be additional
entities that are also contributing causes to the patterns of events). If its
existence cannot be established, then science can return to step three to try
again.
For a Type III or Type IV entity: if a predicted pattern of events is
scientifically observed in an experiment, then this positive result is a
"confirmation" for the hypothesis. A confirmation makes it reasonable
for belief in the postulated hidden entity to marginally increase. If a series
of predicted patterns are all confirmed, and none are disconfirmed, belief in
the postulated hidden entity can become substantial, but should never reach
100% certainty. If a predicted pattern of events is looked for and found to not
exist, then this negative result is a "disconfirmation" for the
hypothesis. Unless a disconfirmation can be explained by human error (in the
prediction, or in the experiment design, or in the observation), this
disconfirmation makes it reasonable for belief in the postulated hidden entity
to marginally decrease.
Under
certain circumstances (where a prediction is carefully deduced, the experiment
is well designed, and no scientific knowledge involved in step five can be
reasonably faulted instead of the hypothesis) a disconfirmation makes it
reasonable for scientists to conclude that the hypothesis is proven false and
the entity does not exist. The inference to such a negative conclusion has a valid
deductive form, superficially similar to that of abduction, which is called
"modus tollens":
If P, then Q.
But Q is false.
Therefore, P is false.
Let P be
the hypothesis "this hidden entity exists" and Q be a prediction
deduced from this entity's existence. If this prediction is discovered to be
false by an experiment, then Q is false and therefore P must also be false:
that hidden entity does not exist. This "falsification" will force
science to return to step three to either modify the hypothesis or to entirely
abandon the hypothesis for some other alternative hypothesis. You can read more
about scientific experiment in "Experiment
in Physics".
We have
already defined the genuine scientific observation. A genuine scientific
hypothesis is a hypothesis that is designed to explain a natural pattern
already scientifically observed, and is testable by the scientific method,
outlined above. The statement of the natural pattern discovered in stage one is
not a hypothesis, although clumsy use of words sometimes results in labeling a
scientific law as a hypothesis. The discovery of a natural pattern is not an
explanation -- it is what needs an explanation. It is possible to "explain"
a single event by holding a natural pattern responsible (the leaf fell off the
tree because trees lose their leaves in the fall). However, a pattern of events
cannot really explain why one event in that pattern did happen. While much of
science is focused on discovering and describing natural patterns, a field of
study does not become a scientific field until it proposes and tests
hypothetical explanations for natural patterns.
A
hypothesis is scientific when it is treated by investigators as scientific:
when it is developed and tested using the scientific method. For example, the
Greek philosopher Democritus promoted the idea that all natural things were
made of tiny invisible atoms that cannot themselves be divided. But the
arguments which Democritus and fellow atomists gave for this idea only had
deductive forms and appealed to allegedly "necessarily true"
premises, and they did not experimentally test their idea. The atomic theory
did not become scientific until the late 1800s.
There are
many ways that people can prevent their hypothesis from being genuinely
scientific. For example:
(1)
Offering an explanation for phenomena that have not been scientifically
observed;
(2) Postulating an entity that has no clearly defined identifying qualities;
(3) Postulating an entity that would not be responsible for any unexpected
natural patterns;
(4) Postulating an entity so contradictory against established scientific
knowledge that experimental testing is impossible;
(5) Refusing to deduce predictions from the supposed existence of the
postulated entity;
(6) Ensuring that any predictions are either vague, difficult to experimentally
test, or unsurprising;
(7) Ignoring any prediction that turns out to be false;
(8) Modifying the hypothesis just enough to be able to afterwards
"predict" a bad experimental result.
A
"theory" consists of several hypotheses that are interrelated and
support each other in order to provide a fuller explanation of a range of
phenomena in some field (chemistry or astronomy or psychology or archaeology,
etc.). For example, the theory of natural selection in biology consists of a
large number of hypotheses about organisms and how they interact with their
environment. A theory is scientific so long as all of its hypotheses are
scientific. It should be noted that items of knowledge from logic or
mathematics are used in a theory, but they are not hypotheses, since they are
not postulates about hidden entities. However, logical or mathematical
principles may be modified or replaced within a theory, if the theory's
development requires these changes. For example, a theory may be able to
explain some new natural patterns only if it uses a different mathematical or
logical system. In this sense, mathematical and logical principles could be
considered as "testable" against scientific evidence, because a
theory's ability to explain the evidence can occasionally require modifying
these principles. But there is no way to directly test any logical or
mathematical principle against evidence -- by themselves, apart from all
hypotheses, these principles make no claims about nature and they are
compatible with any natural events.
We can
also ask whether a scientific theory can ever lose its status as scientific.
Some philosophers, including Karl Popper, have argued that a scientific theory
must continually be used to generate new predictions and be tested. But this is
not a reasonable standard, since most of the established body of scientific
knowledge no longer receives serious experimental testing. One serious event
can cause a once scientific theory to lose its status: A pattern of nature is
discovered which the theory ought to be able to explain, but the scientific
community ignores this need and does no inquiry into whether the theory really
can explain it. A theory which ignores new patterns of nature will likely be
replaced eventually, because a rival scientific theory will emerge which does
succeed in explaining the new patterns and gain credibility quickly with these
successes.
A
"paradigm" consists of several theories that are interrelated and
support each other in order to provide the fullest explanation of the widest
range of phenomena in some field. For example, biology's current paradigm is
evolution, which incorporates theories about natural selection, reproduction by
genetic inheritance, DNA mutation by random errors, and other theories about
living organisms. A paradigm is scientific so long as all of its theories
are scientific. Each scientific field is typically dominated by one
paradigm for a time, when a large majority of scientists in that field accept
only this paradigm. Occasionally, a field may have multiple scientific
paradigms competing for dominant status, and at other times a field might have
no scientific paradigm that is accepted by even a significant minority of
scientists.
The only
requirement that a theory must meet to be scientific is the requirement that
the theory's hypotheses are all designed to explain scientifically observed
natural patterns and they are testable by the scientific method. However, there
are some additional criteria which enhance the scientific value of a theory or
paradigm. These additional criteria are often labeled as the "pragmatic
criteria." The most important criteria are:
1. Logical
Coherence. There should be a very high degree of logical coherence among a
theory's established hypotheses, and among a paradigm's established theories.
If there are logical contradictions between established principles of
scientific knowledge, then those contradictions should be eliminated. All other
things being equal, a scientific theory with no internal logical contradictions
is a better scientific theory. Some scientific revolutions occur because
scientists notice such contradictions and resolve them by dramatically changing
previously established principles of knowledge. For example, Einstein developed
portions of his theory of relativity by noticing that the constant speed of
light (required by electrodynamics) is incompatible with the principle of
additive velocities (required by classical mechanics): light must have the same
speed for all observers no matter how an observer is moving, so much of
classical mechanics must be false. You can visit a website about science and "Thought
Experiments".
2.
Predictive Power. There should be a very large amount of predictions made by a
theory or paradigm. There are two benefits to this "predictive
power": first, more predictive power means a better chance of becoming highly
confirmed (or proven false); and second, a theory that successfully explains a
much wider range of natural phenomena will be much more reasonably persuasive
than a theory that can explain only a small range of phenomena. You can visit a
website about science and "Predictive
Power".
3.
Physical Unification. There should be very wide range of phenomena unified by a
theory or paradigm. For a while, a science may treat one natural pattern very
differently than another pattern, but then a new theory arrives which shows how
these two patterns are really the same pattern. For example, Newton's theories
of motion unified the motions of heavenly objects with the motions of earthly
objects, treating their patterns as all obeying the same basic laws of motion.
Another example is how James Clerk Maxwell's theory of electrodynamics showed
how visible light is the same sort of radiation of photons as all other forms
of radiation. Most of modern physics heavily depends on this persuasive power
of physical unification. You can visit a website about science and "Unification".
4.
Ontological Simplicity. There should be a very small number of entities
postulated by a theory or paradigm that are required to explain a wide range of
phenomena. If two theories can both explain the same phenomena, yet one theory
postulates far fewer entities, that theory appears to be more believable than
the other. The value of simplicity is probably rooted in ordinary practical
common sense: the simpler explanation is more believable, will probably suffer
from fewer internal contradictions, and will be easier to prove false. The more
complex theory appears too ad-hoc and too well-designed -- arousing the
suspicion that the theory was really designed to prevent its falsification.
Also, rationality itself seeks unity behind diversity (e.g. "everything is
made of atoms" or "there is ultimately only one natural force causing
everything"). You can visit a website about science and "Simplicity".
Lecture Two:
Scientific Realism
Naturalism
cannot be a defensible worldview unless some kind of scientific realism is
valid. Unlike positivism, which holds that science should only attempt to know
nature's observable patterns, scientific realism holds that science should also
try to know, and partially succeeds in knowing, about hidden entities behind
these patterns. Scientific realism is the view that the entities postulated by
highly confirmed scientific hypotheses really do exist, and have the properties
more or less as described by these hypotheses. You can read more about "Scientific
Realism".
Scientific
realism is always tempered by fallibilism, the
reminder that scientific knowledge is imperfect and could be modified by future
science. But this proclamation that science is fallible and revisable can
inspire scientific anti-realism.
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Objection One by the Scientific Anti-realist The
scientific anti-realist can argue as follows: If science is always fallible,
then there never is a reason to believe that it discovers truths. Unless it
discovers truths, science cannot reasonably claim that the things that its
theories try to describe actually do exist. So we should not think that the
things that science talks about really do exist. This argument is called the
"Pessimistic Induction": all past scientific theories have been
shown to be false, so all present and future theories will likely be false as
well. What is
at stake here? If this argument cannot be refuted, its victory leads to
complete skepticism about science and refutes philosophical naturalism. Reply by
scientific realism: The scientific realist should reply that perfect
knowledge of truths about things is hardly required for reasonably believing
that they exist. After all, we have practical reliable knowledge about
matters like refining iron from ore, and it is quite reasonable to believe
that iron exists. Science is just the extension of practical reliable
knowledge. |
This reply
to the first objection by scientific anti-realism is the best place to begin
explaining why scientific realism is reasonable. There are several good reasons
for accepting scientific realism. Joined together, they provide the
justification for scientific realism and hence for philosophical naturalism as
well.
1. It is
common sense to believe in hidden causes for observable patterns. Ordinary
common sense consists of reliable practical knowledge about not just the easily
observable patterns of nature but also about many of the things responsible for
those patterns. We are very good at investigating the hidden causes of events
in order to reveal them: what caused the window to break, what caused the loud
noise outside, what caused the dog to bark, etc. Ordinary intelligence assumes
hidden causes for observable events and applies methods of investigation to
reveal these causes by bringing them into our experience. We are naturally
curious about what causes interesting events, and we are especially interested
about the causes of patterns of events. Human intelligence is very good at
detecting and focusing on natural patterns, and we can explain a single event
by noticing that this event should be expected since it is part of a pattern.
But intelligence usually goes farther, not stopping at patterns, and seeks the
hidden causes of patterns. What animals keep causing those patterns of tracks?
Which tree produces those consistently tasty nuts? Which clouds always cause
the worst rainstorms? The search for hidden causes of patterns requires the
application of abductive inference.
2.
Intelligence frequently discovers the hidden causes of natural patterns.
Intelligence discovers hidden causes so frequently that the human brain is now
highly evolved with fairly efficient curiosity and inquiry techniques that
children instinctively use for survival and play, and adults refine these
techniques into science. The abductive belief in hidden causes is so useful for
practical reliable knowledge that intelligence cannot function without such
instinctive practical belief. This practical belief in hidden causes explains
why science also requires the application of abductive inference and why we
provisionally accept the conclusions of confirmed abductive inferences. Making
a hypothesis about a hidden cause is an intelligent effort to understand
nature, and it is intelligent to provisionally accept the existence of a hidden
cause that is postulated by a confirmed hypothesis. Science is merely the
extension of investigative methods of ordinary intelligence, and scientific
realism is therefore demanded by intelligence.
The
limitation of this argument for scientific realism is that ordinary
intelligence deals with the practical, everyday world of directly observable
objects. We know what it is like to verify beliefs in hidden causes, since we
frequently reveal these causes in direct experience after investigation. Some
sciences only deal with directly observable objects -- their hypotheses and
theories only postulate Type I entities -- but most sciences also postulate
causes that are not directly observable: the Type II, III, and IV entities. Should
we also be realists about instrumentally observable entities, and about
non-observable entities too? Some scientific anti-realists say no.
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Objection Two by the Scientific Anti-realist The
scientific anti-realist can argue as follows: Sciences about observable
natural patterns and responsible entities that could be directly observed are
legitimate sciences, but scientific realism should stop there. We should only
be realists about what can be positively verified in our direct experience.
The sciences should not try to describe Type II, III, or IV entities, and we
should not think that such things really do exist. What is
at stake here? If this argument cannot be refuted, its victory leads to the
type of extreme empiricism called scientific positivism or constructive
empiricism: only natural observable patterns and the directly observable
entities causing those patterns really exist. This scientific positivism is a
kind of philosophical naturalism, but a very limited kind. Reply:
The scientific realist should reply that even if empiricism's demand for
observable proof is taken so seriously, it is possible to reasonably believe
in at least some Type II and Type III entities. First, instrumentally
observable entities can be trusted if the instruments can be trusted, and we
can reasonably trust many scientific instruments by methods of direct
observation alone. Second, if it is reasonable to believe in many Type II
entities, it may be reasonable to believe in Type III entities, since
scientific progress frequently converts unobservable entities into
instrumentally observable entities, increasing our confidence in postulating
Type III entities. |
This reply
to objection two has two stages: First, defending instrumentally observable
entities; and second, defending unobservable entities that potentially could
become instrumentally observable entities.
First, why
should we trust telescopes and microscopes? We come to trust them in the same
way we trust our senses: by comparing the information we get from them as we
use them under different conditions. We can learn that we have good eyesight by
checking whether we can perceive things from farther away as well as we can
when we perceive them nearer to us. We can learn whether a pair of glasses
improves our eyesight, and we trust a reliable pair of glasses to show us real
objects in front of us (should we think that putting on glasses suddenly
presents us with a completely false version of reality?) Similarly, we can
learn that a telescope accurately depicts a distant tree by comparing that
observation with own perception of that tree using our eyes up close. Might the
telescope change the way it works when we turn from looking at distant trees to
looking at the distant moon to see craters? Skeptics about Galileo's observations
of moon craters, sunspots, and moons of Jupiter suggested that a telescope
might not work properly when aimed upwards. But direct inspection of the
telescope and its parts shows that a well-constructed telescope does not change
its functioning if it is pointed upwards into the sky. Some anti-realists have
argued that trusting an instrument necessarily requires acceptance of a
complete theory about why the instrument works, but such a theory would require
postulating non-observables in the first place, begging the question in favor
of scientific realism. The reply by the scientific realist is that it is
valuable, but not necessary, to have a theory about an instrument's
functioning. Summing up, we should be scientific realists about instrumentally
observable entities because:
3. An
instrument such as a telescope or a microscope can be tested and trusted by
ordinary methods, already described above, that only involve direct
observation.
Of course, this reply only is relevant to instruments like telescopes and
microscopes that detect very distant or very small objects, however (along with
other instruments that amplify the senses, such as microphones for making
sounds louder). This reply does not apply to other kinds of scientific
instruments that detect things like electrical current or air pressure or
chemical acidity. More arguments, explained below, will describe how scientific
realism deals with these kinds of instruments.
Second,
why should we postulate unobservable entities even though there currently is no
way to even instrumentally observe them? Our experience with inventing and
using sense-amplifying instruments demonstrates that nature consists of things
much smaller and much larger and much farther away than our human senses can
detect. And since the power of our instruments has grown over time, revealing
more and more of nature to us, it is reasonable to believe that much of nature
has not yet been observed, directly or instrumentally. Why shouldn't science be
permitted to make hypotheses about possible entities in that yet-to-be-observed
part of nature? Furthermore, many scientific hypotheses about Type III
entities, confirmed by experiment, have later been observed by scientific
instruments invented after the original hypothesis. Examples: Atoms were
proposed before they could be observed by the scanning tunneling microscope;
genes were proposed as the transmitters of biological information before DNA
was observed by microscope; planets around other stars were proposed before
they were observed by more powerful telescopes. Since many Type III entities
proposed by confirmed hypotheses have later been verified by improved
instruments, it is reasonable for science to propose hypotheses about Type III
entities and believe that these entities exist when these hypotheses are highly
confirmed by experiment. Recall the "Pessimistic Induction" from
Objection One by the Scientific Anti-realist? The scientific realist can in
turn propose the "Optimistic Induction":
4. Since
many successful hypotheses about Type III entities have later been verified, it
is reasonable to conclude that many more hypotheses proposed in the future
about Type III entities will also someday be verified by more powerful
instruments.
Of course, we cannot yet know which current hypotheses about Type III entities
will be verified in the future, but at least it is reasonable for science to
try to postulate them now. As for Type IV entities, this Optimistic Induction
argument does not help. There are no cases where confirmed Type IV entities
have later been verified by improved instruments. This lack of cases is not
surprising. By definition, we do not have any conception of what it could
possibly be like to instrumentally observe Type IV entities (what would seeing
gravity, or a black hole, be like?). So we would not try to invent instruments
to observe them -- how could we confirm that we succeeded in observing them
without any conception of what to look for?
The
scientific realist does want to defend the reasonableness of postulating Type
IV entities, but that requires a separate defense against scientific
anti-realism, to be explored in the succeeding modules.
The
scientific anti-realist has more arguments against Type III and IV entities.
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Objection Three by the Scientific Anti-realist The
scientific anti-realist can argue as follows: Sciences may postulate and
confirm hypotheses about Type I and Type II entities, but scientific realism
should stop there. Consider how abduction works: we can never prove a
hypothesis true using abduction, since there are potentially many more
hypotheses, not yet thought by anyone, which could explain the same predicted
patterns equally well. In fact, for any highly confirmed hypothesis H about a
Type III or Type IV entity, there are so many potential hypotheses with the
same empirical adequacy (able to explain the same natural patterns) that the
marginal increase in belief gained by H should be zero or very close to zero
-- there is no sufficient reason to believe in that entity's existence. Even
if the sciences should be permitted to postulate such entities (maybe to
increase logical coherence or predictive power), we should not think that the
Type III or Type IV entities postulated by science really do exist. What is
at stake here? If this argument cannot be refuted, its victory leads to the
type of rational empiricism called instrumentalism: only natural observable
patterns and the directly or indirectly observable entities causing those
patterns really exist. Instrumentalism is a kind of philosophical naturalism,
but a very limited kind. Reply:
The scientific realist should reply that even though there are many potential
hypotheses with the same empirical adequacy as any well-confirmed hypothesis,
the real scientific value of a hypothesis, and hence its long-term
credibility, lies in its pragmatic value: how well it meets the additional
criteria of logical coherence, predictive power, physical unification, and
ontological simplicity. |
Scientific
anti-realists are impressed by the fact that many (perhaps an infinite number)
potential hypotheses can explain any particular set of natural patterns. They
try to conclude that the probability of any one of the hypotheses being
accurate must be very close to zero.
Pierre Duhem (1861-1916), the French philosopher and scientist,
was this type of scientific anti-realist. He argued that some sciences, such as
chemistry and physics, can never reasonably claim to have proven that their
hypotheses are true. Only direct or instrumental observation can prove the
existence of hypothesized entities, under the best of experimental conditions,
but chemistry and physics try to describe entities that cannot be observed
(what we have here been calling Type III or Type IV entities). Duhem realized that hypotheses about Type III and IV
entities can never be proven true, since there are always other possible
hypotheses that could explain the same observed natural patterns. We have
already explained why the nature of abductive inference prevents proving that
its conclusions are true. Since there are always many potential hypothetical
explanations for the same observable phenomena of nature, scientific hypotheses
are "underdetermined" by the currently available evidence. Duhem's underdetermination
argument is simply the philosophical point that no hypothesis about a Type III
or Type IV entity (the "unobservables") can
be proven true. Duhem went farther than this point
about abductive logic, however. Duhem claimed that
since the available evidence cannot determine which scientific hypothesis about
unobservables is correct, no scientific hypothesis
about unobservables should ever be believed. In other
words, even a highly confirmed scientific hypothesis cannot be reasonably
believed at all. Science cannot ever get us even close to the truth. In recent
philosophy of science, van Fraassen has revived and
extended these arguments against scientific realism in order to support his own
"constructive empiricism". Some of his writings, and writings about
his philosophy, are online here: http://www.princeton.edu/~fraassen/
The
scientific realist replies to this argument by pointing out that empirical
adequacy by itself does not produce much real credibility. For any given
hypothesis, it is suspiciously too easy to artificially generate a rival
hypothesis that can explain exactly what the given hypothesis can already
explain. But can the artificial hypothesis cohere with the larger theory of
which it must be a part? Can it make any more unexpected predictions? Does it
offer any physical unifications, or only disunifications?
Does it only increase ontological simplicity? There are far fewer rival
hypotheses that can be artificially generated which meet these severe criteria
-- and scientists continually try to create them and test them too.
5.
Hypotheses about unobservables that continually
increase their empirical adequacy and cohere well with larger theories and
paradigms, while revealing a simpler reality behind the phenomena, deserve
greater credibility. If the scientific anti-realist tries to
continue to argue that even the possibility of a few alternative hypotheses
which meet this much higher standard should restrain how much credibility any
of them receive, this is not a new argument, but only repeats the unoriginal
observation that abduction cannot ever prove any hypothesis. But we still can
reasonably have some degree of belief in the most successful hypothesis
available now.
What is
our alternative to provisionally accepting the best hypotheses we have now?
Consider what the scientific anti-realist is claiming -- if we really shouldn't
think that any hypothesis about unobservables is
believable at all, then we are denying that there is any underlying cause for
natural patterns. Without underlying causes, it is a sheer miracle of chance
that natural patterns persist and a complete mystery of luck that many
hypotheses successfully anticipate more natural patterns. The scientific
realist can offer a further argument at this stage:
6. If the
entities described by highly confirmed hypotheses really exist, that would
explain why science's best hypotheses are so empirically adequate. And
science's best hypotheses are very empirically adequate. Therefore, the
entities described by highly confirmed hypotheses really do exist. This
argument for scientific realism has the form of an abductive inference: If P,
then Q -- and Q is true -- so P is also true. Of course, this
"meta-abductive" argument, also called the "no miracles
argument," cannot prove its conclusion. There may be other possible
explanations for why science can produce hypotheses that have high empirical
adequacy. The scientific anti-realist does have an alternative explanation for
the existence of highly confirmed hypotheses.
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Objection Four by the Scientific Anti-realist The
scientific anti-realist can argue as follows: It is reasonable to believe
that there are hidden portions of nature where unobservable causes for
natural patterns do exist. But we should not believe that any highly confirmed
hypothesis approximately describes these unobservable causes. For Type III
and Type IV entities, their only properties relevant to the empirical success
of hypotheses about them are those properties which require these entities to
obey certain natural laws. After all, it is only the natural laws that are
used for formulating predictions For example, it doesn't matter what an
electron is really like so long as its behavior always obeys certain laws. In
fact, the entity that really does exist, if it isn't an electron, only has to
obey those same laws, since it really has been the laws themselves that enjoy
high confirmation. But it possible to imagine many alternative sorts of
entities quite different from the electron that still obey the same laws that
electrons are supposed to. Therefore, while unobservables
exist, and science is reasonable to postulate unobservable entities, we
should not think that the Type III or Type IV entities postulated by highly
confirmed hypotheses really do exist. What is
at stake here? If this argument cannot be refuted, its victory leads to the
type of rational empiricism called pragmatism: only natural observable
patterns, the directly or indirectly observable entities causing those
patterns, and hidden unknowable causes really exist. Pragmatic realism is a
kind of philosophical naturalism, and it is a candidate for being the most
reasonable type of philosophical naturalism. Reply:
The scientific realist should reply that even though it is possible to
imagine alternative entities for playing the role of an electron, the
hypothesis about the electron's existence only describes electrons in terms
of the laws they all must exactly obey. The only properties that science
attributes to electrons are the properties of obeying those particular laws.
In other words, an electron simply is whatever entity obeys all of the
electron laws. Any alternative imagined entity that still obeys the same laws
is an electron too! Therefore, there are really no alternative hypotheses
about alternatives to electrons -- there can only be rival hypotheses about
genuinely different entities that obey somewhat different laws, and those
have to be tested just like any hypothesis. It is reasonable to believe in
the existence of unobservable entities postulated by highly confirmed
theories. |
In order
to refute objection four by the pragmatic realist, the scientific realist here
tries to claim that a hypothesis's conception of a postulated unobservable
entity consists only of the laws that entity must always obey. But this claim
has a steep price. If correct, this claim implies that all of the real work
done by a hypothesis to make predictions is actually done by the natural laws
postulated. The unobservable entity itself has no role to play in scientific
method. Of course, whatever unobservable entities really exist do supply causes
for natural patterns, and that is a crucial role. But only the natural laws --
those numerous equations -- proposed by hypotheses are actually used for
formulating predictions about natural patterns. These natural laws are what are
really being tested in the experimental method, and according to pragmatic
realism, highly confirmed natural laws deserve credibility -- nature really
does display habitual regularities as (approximately) described by scientific
laws.
But is
scientific realism the better choice over pragmatic realism? The pragmatic
realist approves the existence of verified Type I and II entities, grants the
existence of unobservable entities responsible for natural patterns, and agrees
that science should propose and test hypotheses about unobservables.
Scientific realism additionally claims that it is reasonable to believe that
highly confirmed hypotheses fairly accurately describe unobservable entities.
But what descriptions are given by such hypotheses? The only descriptions that
matter are descriptions of the natural laws these entities obey, and the
pragmatic realist already encourages belief in those highly confirmed natural
laws. So what remains of any real difference between pragmatic realism and a
reasonable scientific realism? Perhaps none.
The "demarcation
problem" is the philosophical problem of justifying a reasonable
standard to judge whether an explanation (a hypothesis, or a theory or a
paradigm too) is a scientific explanation, or not scientific at all (such as
pseudoscience or religion or mythology, etc.). There is an easy way to
seemingly solve the demarcation problem: justify an account of scientific
method (such as the six-step method described in module 3) and then declare
that only hypotheses that are testable by this scientific method qualify as
scientific. Sounds easy -- but the most difficult part is precisely justifying
an account of scientific method. Philosophers and scientists have been trying
since Aristotle to accomplish this. A philosophical account of scientific
method must explain (1) how hypotheses that survive trial by this method are
more likely to be true, and also (2) how hypotheses that do not survive trial
by this method are more likely to be false. The first task is the
philosophical problem of explaining why highly confirmed scientific hypotheses
have a better chance of accurately describing real entities. We have covered
this task in modules five and six. The philosophy of science that survived this
task is "pragmatic realism."
The second
task is the philosophical problem of explaining why disconfirmed scientific
hypotheses probably fail to describe real entities. Unless the scientific
method can at least help scientists to judge which hypotheses are false,
science cannot be any help deciding what reality is like.
Pierre Duhem (1861-1916), the French philosopher and scientist,
argued that hypotheses about Type III or Type IV entities -- the "unobservables" -- can never be proven false. His
argument started from the fact that no hypothesis can really be tested by
itself, apart from the larger theory of which it is a part. Duhem,
and other philosophers since, are concerned with the worry that a hypothesis
cannot really be tested and hence never proven false (or never shown to be
probably true either). It is true that a hypothesis cannot be properly tested
without also using some other items of established scientific knowledge, as
mentioned in step five, "experiment". For example, an experiment to
test for whether water exists on Mars depends on already established knowledge
about how to detect water using scientific instruments: the signs that water
will give from a distance, the effects of those signs on an instrument, how the
instrument works, etc. When an experiment is designed, the logical form of the
experimental inference is deductive. In the following table, the deduction on
the left illustrates the reasoning when a prediction is experimentally
confirmed, while the deduction on the right illustrates the reasoning when a
prediction is experimentally disconfirmed.
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1.
Scientific knowledge item A. |
1.
Scientific knowledge item A. |
In the
second example of a disconfirmation, the premises 1-4 cannot all be true. At
least one of them must be false, assuming no experimental error. But which one?
Remember, all scientific knowledge is fallible. Just because the purpose of the
experiment is to try to test the new hypothesis, this does not mean that only
the hypothesis can be shown to be wrong. Any premise, any knowledge, used in
the design and execution of the experiment can be held responsible for being
false. Reasoning only says that at least one, and perhaps more than one, of the
four premises in this inference must be false. Reason and logic cannot identify
which is false. Of course, if scientists decide to trust the other premises
rather than the new hypothesis, a disconfirmation makes it reasonable for scientists
to conclude that the hypothesis is proven false and the entity does not exist.
But this reasonable conclusion depends on the scientist's decision to trust
prior knowledge. It is also possible for scientists to protect the new
hypothesis by deciding that one of the other premises must be false instead.
Karl Popper's philosophy of falsificationism demanded that scientists must always
discard the new hypothesis, but neither logic nor actual scientific practice
requires this drastic approach. Scientific method must permit scientists to
make judgments about which parts of theories should be changed. Because any
single hypothesis needs assistance from other parts of a larger theory in order
to be tested [what is now called the "Duhem-Quine
thesis"], only entire theories really confront experimental evidence.
Theories will gradually change over time as scientists selectively judge which
parts require modification or replacement in order to continue to make
successful predictions.
In earlier
modules, we have already seen how hypotheses are linked together to form
theories. In the 20th century, philosophers also began to emphasize how
theories are linked together into paradigms. The best example is evolutionary
theory. In order to justify the biological theory that natural selection is
responsible for gradual species modification and elimination, evolutionary
scientists appealed to non-biological theories. For example, 20th century
geology confirmed that the age of the earth is at least 4 billion years and
that there has been dramatic change to earth's surface and environments over
that time. Another excellent example is 20th century physics, in which theories
about subatomic particles were confirmed by sophisticated experiments only if
physicists could already assume the validity of other theories about how their
highly technical instruments worked, which in turn required confidence in many
more theories of physics. The classic example is the "bubble chamber",
which is supposed to show the particles created by collisions: the distinctive
trails of bubbles left in the wake of these particles, according to theory,
reveals the nature of these particles (especially the duration of their
existence and their susceptibility to magnetic fields). Of course, a physicist
could use the "evidence" of bubble chamber tracks to confirm a theory
about particle collisions only if she already assumed the validity of other
theories about these particles and their behavior in bubble chambers. This is
the situation described by Duhem, and later
emphasized by Kuhn: Many theories of physics are together used in the search
for confirmations for one new physical theory. Therefore, the problem of
disconfirmation already discussed above for a particular hypothesis is
analogously repeated at the higher level for a particular theory:
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1.
Theory of physics A. |
1.
Theory of physics A. |
In the
second box above, the conclusion states that the new theory has a
disconfirmation. But does it really? That depends on the judgment of the
scientists. It is possible for scientists to refuse to accept a disconfirmation
and instead try to place the blame for the predictive failure upon theory A, B,
or C. If any of these other theories are modified instead, the disconfirmation
could be made to go away and become a confirmation instead. Following Kuhn, let
us call a group of theories in a field of science, which heavily depend on each
for mutual support, a "paradigm". [The philosopher Lakatos instead talks about "scientific research
programs", which is a similar notion.] The philosophical problem presented
here can be stated like this: how is it possible for a paradigm to proven false
by experiment, if its component theories are continually used to protect each
other against disconfirmations? This is not merely a hypothetical problem.
Historians of science have easily exposed how paradigms gradually change over
time as its component theories are modified in order to keep up with new
evidence. You can read a webpage about "Scientific
Progress".
Popper
supplemented his theory of falsificationism with the
idea of the "crucial experiment", in which theory A can defeat theory
B by receiving a confirmation from the very same experimental outcome that
causes theory B to suffer a disconfirmation. In his writings, he relies on the
example of confirmation of Einstein's theory of relativity, which correctly
predicted (unlike the Newtonian theory) that the sun would bend light from
distant stars. For Popper, this single crucial experiment justified the
complete replacement of Newton with Einstein. However, Popper's notion of a
crucial experiment between two theories presupposes that both competing
theories accept the validity of other theories about how to accurately observe
the shifting of the position of stars which is (allegedly) caused by the
hypothesized bending of starlight by the sun. In other words, both the Einsteinian and Newtonian theories agreed on some other
physical theories about the crucial experiment, so that the Newtonian theory
was logically forced to admit disconfirmation (and, according to Popper, admit
complete falsification as well). It is very important to realize how the Einsteinian and Newtonian theories were not entirely
distinct paradigms -- they actually shared much theoretical ground, and hence
they competed on the same experimental "playing field". While not
very frequent, the history of the sciences has witnessed some of these dramatic
theoretical changes, during which a paradigm is suddenly replaced by a new
paradigm -- in what is called a scientific revolution -- as philosopher and
historian of science Thomas
Kuhn has described.
But what
about a quite different situation, when two distinct paradigms are competing in
a single field of science? In this situation, there seems to be little
possibility for a "crucial experiment" or any serious competing
experiment at all. Consider the following problem:
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1.
Theory of physics A from paradigm X. |
1.
Theory of physics E from paradigm Y. |
In this
situation, the scientists who accept paradigm X (hereafter lets call them 'X
scientists') refuse to believe that scientists who accept paradigm Y
(hereafter, 'Y scientists') have any legitimate way of getting confirmations
for their preferred theories. And vice-versa: Y scientists do not believe that
X scientists can legitimately get confirmations for their preferred theories.
Here's an example in the philosophical literature: consider the X scientists
who accept a paradigm of Western medicine (eg., tiny
living organisms cause diseases) and the Y scientists who instead accept a
paradigm of Eastern medicine (eg., imbalances of
internal energies cause disease). And let us suppose that both parties are
really scientists -- they are using the same scientific methodology. X
scientists will not be impressed by alleged "experiments" that
"confirm" any relationship between meditational yoga and restored
health, and Y scientists will not be impressed by alleged
"experiments" that "confirm" any relationship between
antibacterial medicines and restored health. In this hypothetical scenario (not
far from the real situation, actually!), these paradigms do not share enough
theoretical ground to permit the possibility of a crucial experiment. They
cannot be compared against each other by any simple measure of experimental
evidence, because each paradigm rejects the existence of experimental evidence
supporting the other side's paradigm.
Kuhn describes
this philosophical problem as "incommensurability": if a paradigm
encompasses all theories that it uses to create any evidence relevant to its
confirmation (let us call this bloated paradigm a "totalitarian
paradigm"), then it cannot be measured against any other paradigm. If a
field of science happens to have multiple totalitarian paradigms rivaling each
other, this field will not make much scientific progress (and optimistic
scientific realism will yield to pessimistic scientific antirealism and
instrumentalism). Which fields of science currently suffer from this sort of
situation? Psychology has seen a variety of totalitarian paradigms during the
past 120 years, although behaviorism has lately dominated. Economics can hardly
be called a science because of the way that various totalitarian paradigms
(incorporating moral and political views as well) only talk past each other. In
the natural sciences, quantum physics has occasionally seen the realist and
antirealist camps sharply disagree over the interpretation of experimental
evidence regarding the particle or wave nature of light (the proposed
compromise, that natural things really are both particles and waves, is only
the pessimistic peace offering of antirealism).
Because
scientists can protect some hypotheses by modifying or discarding others, and
they can protect some theories by modifying or discarding others, some
philosophers have claimed that experiments do not really determine the validity
of a new hypothesis. If this claim has merit, then this problem with
experimentation causes more doubt whether either scientific evidence or reason
really decides which hypotheses or theories should be believed. If the
empirical evidence does not control which hypotheses should be believed, what
really makes scientific theories any different from other kinds of theories
that some people want to believe in, such as religions or superstitions or pseudosciences such as astrology?
Recall
what is at stake here: A philosophical account of scientific method must
explain (1) how hypotheses that survive trial by this method are more likely to
be true, and also (2) how hypotheses that do not survive trial by this method
are more likely to be false.
We have
tried to formulate a philosophical account of scientific method that explains
how this method rationally decides what hypotheses deserve belief, and which
don't. But what happens if this account fails to deliver on its promises? What
if a thorough analysis of scientific method, as scientists actually operate, reveals
that scientists can protect hypotheses and theories? Then we are in a situation
where philosophy and reason cannot deliver an account of how science works
(maybe instead philosophy and reason only can describe some ideal utopia where
science should rationally work, but that would not be our actual world of real
people). So where can we go to learn how science actually works in the
real world? Who can discover why some theories and paradigms are accepted and
promoted by science?
In the 1970s and 1980s, social
scientists undertook this effort to explain how science REALLY works. Much of
this effort goes under the label of "Sociology of Science" of
"Sociology of Scientific Knowledge". See this website on "Social
Dimensions of Scientific Knowledge". Sociology is a discipline which,
among other things, attempts to understand the activities of social groups in
terms of the power relationships existing between people. In its crudest form,
sociology of science would explain that scientists believe paradigms because
professing such beliefs bring the rewards of social and material status. Nature
and truth are almost entirely eliminated from such explanations -- what nature
is doing has little to do with the theories scientists promote, and there is no
way to tell what the "truth" is anyways.
Inspired
by this sociological perspective on science, other philosophers and social
scientists have investigated science's hidden assumptions, looking for premises
in scientific reasoning that do not have an origin in science itself, but must
have some other origin (for example, an origin in background cultural biases
and prejudices). For example, the Aristotelian assumption that reproduction
involves the union of a passive formless egg from a woman and an active
essence-carrying sperm from a man (giving men all the credit for making human
babies) was capable of retarding knowledge of reproduction until into the 20th
century. Feminist sociologists and philosophers have successfully exposed a
wide variety of gendered assumptions having no basis in empirical evidence.
Interestingly, these cultural critiques of science depend on being able to
distinguish bad prejudiced science from good unprejudiced science, and hence
they still assume that some science can be conducted on the basis of evidence
and reason alone. These feminist critiques still have respect for scientific
method, therefore, and only demand scientific reform, not replacement.
However,
some philosophers demand replacement. Some have proposed that the scientific
method itself must be evaluated as a component part of current scientific
paradigms. After all, only by assuming its validity can scientists use
scientific method to achieve confirmations of its theories. This is a
totalitarian view of paradigms taken to its logically ultimate extent. By
viewing scientific method itself as just another component theory of modern
scientific paradigms, we can begin to wonder whether scientific paradigms must be
deeply incommensurable with any rival paradigm that uses a very different
system of justification for its own theoretical conclusions. The alleged "psuedosciences" might really just be rival
totalitarian paradigms, after all.
The best
example of this philosophical problem is the Catholic church's view (from
Thomas Aquinas) that revelations from God are a different but no less valid
method of learning truths than the rational/scientific method of empirical
inquiry into nature. Religious revelation and empirical science can be viewed
as two totalitarian paradigms that nevertheless must reach a philosophical
compromise by each agreeing that neither by itself provides a complete and
final understanding of all reality.
By taking
this philosophical problem of justifying scientific knowledge very seriously,
modern Western science begins to look like any other cultural belief system,
sustained over generations by mere persuasion or coercion, and not pure reason
or absolute truth. If this sociological view of science is correct, then there
is no reasonable demarcation between science and any other belief system, and
hence scientific "knowledge" should not be permitted to have any
greater authority than any other belief system like magic or myth. This view,
which is a kind of "Relativism",
was championed by the 20th century philosopher Paul Feyerabend.
Feyerabend was not a skeptic, since he believed that
plenty of fallible practical knowledge is available to people -- so much
knowledge, in fact, from so many cultural sources, that it is impossible to
find some objective supreme methodological standard to judge which sort of
cultural knowledge is superior to any other.
Lecture Three: Naturalism
is superior to Supernaturalism
Naturalism
is a worldview, a philosophy -- a general understanding of reality and
humanity's place within reality. Naturalism is usually defined most briefly as
the philosophical conclusion that the only reality is nature, as gradually
discovered by our intelligence using the tools of experience, reason, and
science.
Naturalism
emphasizes the progressive and expanding knowledge that observation and science
provides. Science continually revises its understanding of physical reality.
Today's scientists have new conceptions of energy and matter that most 19th
century scientists would have found incomprehensible, and the next century's
scientists will likely demand major revisions to today's best theorizing about
what physical reality is like. Because science's best ideas about reality
undergo improvement, naturalism is a philosophy that requires intellectual
humility: while reality is physical and discoverable by science, naturalism
cannot offer any final and perfect picture of exactly what this reality is
like. Therefore, the primary task of philosophical naturalism is not to
defend science's current best theories about reality -- science itself is
responsible for reasonably justifying its own theories. Philosophical
naturalism undertakes the responsibility for elaborating a comprehensive and
coherent worldview based on experience, reason, and science, and for defending
science's exclusive right to explore and theorize about all of reality, without
any interference from tradition, superstition, mysticism, religious dogmatism,
or priestly authority.
Science
therefore has three close relationships with philosophy. First, when the
various sciences question their ultimate principles and ponder how these
principles can reasonably cohere together, science becomes philosophy and
intellectuals undertaking these problems are both philosophers and scientists.
For example, the founders of the many sciences are all counted as philosophers
as well, and most of the leaders of great scientific revolutions are recognized
as having made major philosophical contributions. Science occasionally is
naturalistic philosophy. Second, when the sciences are under intellectual
attack by jealous rivals offering non-natural hypotheses or unnatural modes of
alleged knowledge, science turns to philosophy for reasoned arguments why
non-natural hypotheses are irrational and unnecessary, and why allegedly
unnatural knowledge is no sort of knowledge at all. Naturalistic philosophy
explains, justifies, and improves scientific method. Third, when the
sciences are under political attack by hostile forces wanting to obstruct
scientific research or inhibit scientific teaching, science turns to philosophy
for staunch defenses of intellectual freedom and democratic secularism. Naturalistic
philosophy constructs and maintains a liberal political order protecting
science.
Naturalism
is a worldview that relies upon experience, reason, and science
to develop its understanding of reality and humanity's place within reality.
Human experience is the ultimate source and justification for all knowledge.
Experience itself has accumulated in human memory and culture, gradually
producing the methods of intelligence called reason and science. Scientific
method is an extension of reason, so reason and science are not entirely
different matters. However, it is useful to distinguish reason and science in
this way: reason is a general term covering the proper use of the rules of
logical inference, while scientific method applies the rules of logical
inference to empirical evidence for drawing conclusions about reality. For
example, if a naturalist refuses to be persuaded by a argument for the
existence of God because that argument violates a rule of logical
inference, this naturalist has used reason to reject the supernatural.
Alternatively, if a naturalist refuses to believe that a supposed miraculous
event shows that God exists because science instead shows that this
event can be explained by natural causes, this naturalist has used science
to reject the supernatural. You can visit this Wiki
website and an atheist
website about various arguments for God's existence.
Have
you heard about the allegedly "quick and easy" ways to refute
naturalism? Here's a quick and handy guide:
1.
Naturalism claims that it takes experience seriously, but in practice it can't
respect religious experience of the supernatural. So naturalism is either
dogmatically prejudiced against supernaturalism or needs supplementation by
religion.
The
naturalist replies: Naturalism relies on experience, reason, and science
working together, and not on any of them operating by themselves. Human
experience is notoriously full of shadowy, distorted, illusory, and deceptive
aspects. All experience should be tested by intelligence, and a naturalist is
not persuaded that alleged experiences of the supernatural are valid. Several
of this website's pages explain how naturalism handles the breadth and variety
of human experience.
2.
Naturalism is about confidence in science, but its theory that "reality is
nothing but what science discovers" is not a hypothesis that can be
verified by any scientific investigation. So naturalism is either self-refuting
or relies on a non-naturalistic dogma.
The
naturalist replies: Naturalism is a worldview based on philosophical
thinking about experience, reason, and science -- naturalism is not just
science or just based on science alone. Here is an analogy: The proposition
that "God is nothing but what the Bible says he is" does not itself
occur in the Bible -- some Christians reach this conclusion only after
theological thinking about the significance and interpretation of the Bible.
Please digest a few of this website's pages about science and reason to
understand philosophical naturalism.
3. If
naturalism were true, human knowledge would arise from the random interactions
of matter, but those interactions could not possibly guarantee truth. So even
if naturalism is true, we could never know it, and we should not assert that
naturalism is true. So naturalism is either self-refuting or relies on a non-naturalistic
dogma.
The
naturalist replies: Naturalism does understand that human intelligence is
fallible and great effort is required for adequately justifying theories about
nature. Nature is hardly just "random" -- its laws permit the
structures and regularities known by science and exploited by technology.
Nature is knowable by natural human intelligence. Whether we should believe
that only nature exists is a separate philosophical question, so please explore
this website's pages.
4.
Naturalism claims that reason is on its side, but naturalists really are just
as dogmatic about nature as supernaturalists are about God. So naturalism is
based on faith as much as supernaturalism, and naturalists should stop claiming
to be more reasonable.
The
naturalist replies: Naturalism does claim that it is more reasonable,
because it is based on experience, reason and science instead of faith. Faith
alone by definition is not reasonable (could the supernaturalist really be
proud to defend dogmatic faith as reasonable??). Naturalism's basic argument is
that (1) we believe that nature exists, (2) there are no good reasons to
believe in the supernatural, therefore (3) we should believe that only nature
exists. Supernaturalists have to either (a) establish that nature does not
exist (some eastern religions try this tactic), or (b) establish that there are
good reasons to believe that the supernatural exists in addition to the
natural. Explore this website's pages to hear why there are no good reasons to
believe that the supernatural exists.Naturalism is
sometimes defined in terms of what is not included in reality: no supernatural
gods or unnatural powers; no spirits; no miracles; no revelations or intuitions
from a transcendent source; and no master design or plan for nature. Naturalism
is a worldview that therefore opposes most religions, since most religions
require belief in the supernatural. Naturalism only needs to contradict
religion about what sorts of realities exist. Naturalism's relationship with
religion and spirituality is very complex, and goes far beyond a simplistic
denial of religion. You can read "Atheism and
Agnosticism".
The
Current Debate between Naturalism and Supernaturalism
The
current debate between naturalism and supernaturalism is very active on a
handful of issues. Some of them are perennial issues, looking now very much
like they did in medieval times, and still shaped by ideas from the ancient
Greeks. Other issues are modern, arising from newer perspectives on nature and
humanity that are only a couple of hundred years old at most. All of these
issues have fresh life and vigor, because current science tells us amazing
things, about the origin and evolution of the universe in general, and of life
on earth in particular. The select issues that we can briefly discuss here
include the origin of the universe, the fundamental laws of the universe, the
evils that humanity suffer, and the moral rules of humanity. Naturalism
disagrees with supernaturalism about how to best explain these issues, and
their debates continue to grow more complex and interesting.
Naturalism
is essentially the philosophical view that the only reality is nature, as
gradually discovered by our intelligence using the tools of experience, reason,
and science. Naturalism keeps pace with science's knowledge in order to
describe what nature is like, and what place humanity has within nature.
Supernaturalism can also try to keep up with science, and the most important
kinds of supernaturalisms do take science carefully into account.
Supernaturalism basically is the theological view that nature cannot be all
that exists, because religious knowledge tells us about a divine reality and
about humanity's relationship with it.
A
simplistic theology dismisses scientific knowledge with the attitude that
religious knowledge is always far superior. For example, a theology based
primarily on priviledged religious experiences or exhalted religious authorities can too easily dismiss scientific
knowledge entirely. Naturalism shouldn't respond to such simple theologies by
dismissing either experience or authority, since naturalism starts from
experience and has respect for scientific authorities. However, naturalism
tests experience using principles of reason and methods of science, and could
never priviledge any experience elevated away from
intelligence. Similarly, naturalism respects scientific authorities for their
commitment to intelligence, and could never exhalt
any scientist admired for genius or wizardry.
Sophisticated
theologies go beyond mere experience or authority to offer intelligent
compromises with knowledge of nature, and some even rely on scientific
knowledge to support their kinds of supernaturalism. The temptation for a supernatural
theology to deal with science is very strong, because the burden of proof in
the debate between naturalism and supernaturalism is on supernaturalism, and
supernaturalism ultimately needs all the help it can get. Why is the burden of
proof on supernaturalism? Consider the basic argument for naturalism:
First,
Nature exists.
Second, There are insufficient reasons to believe that the supernatural exists.
Conclusion: Only nature exists.
Supernaturalists
could try to defeat naturalism by claiming that nature does not exist. Most
supernaturalists have never tried this tactic. The obvious reason for their
reluctance is because any definition of the “supernatural” depends on already
possessing a conception of, and belief in, the “natural.” Otherwise how could
the supernatural be contrasted against anything, and how could the supernatural
be given credit for creating the natural world? The paradigm supernatural
religions (western religions such as Judaism, Christianity, and Islam) require
belief in both the natural and supernatural worlds. The less obvious reason why
supernatural religions are not skeptical towards nature is because those other
religions (such as some varieties of Hinduism and Buddhism), which do argue
that nature is not real, still try to explain the illusion, by giving ultimate
spiritual reality the credit for generating the illusion of nature. By treating
nature as a by-product of genuine spiritual reality, these religions actually
bring nature and spirit into close relationships, tending to result in
theologies that look more like pantheisms. Instead of sharply dividing spirit
from nature, many of these eastern theologies tend to unify them. Genuine
supernaturalisms instead depend on sharp dichotomies between the supernatural
and the natural. For example. the supernatural has no physical properties, need
not obey natural laws, is not constrained by space/time, etc. The natural only
has physical properties, must obey natural laws, is contained within
space/time, and so forth. We are already familiar with the natural world and
what much of it is like. What can religion additionally teach us? Sophisticated
theologies accept the burden of proof and formulate various arguments that the
supernatural exists in addition to the natural. There are three main types of
theologies which pursue distinct strategies.
Theology
Close To The Edge: According to this kind of theology,
religion has similarities with science and even can share much of scientific
method because supernatural hypotheses should compete with naturalistic
hypotheses for rationally explaining the features and events of the natural
world. If hypotheses about the supernatural are better able to explain some
things going on within nature, belief in the supernatural would be reasonable. This
theological strategy seemed plausible during medieval times, but it has now
been driven close to the edge of extinction. Modern science and its
naturalistic hypotheses have proven far more successful. Naturalistic
explanations have been plausibly established for so many features of nature,
from the origins of galaxies, stars, and planets to the evolution of life,
intelligence, and human culture. Now near the brink of elimination, Theology
Close To The Edge can survive only on lingering mysteries in the universe. Even
if the supernatural is no longer needed to explain the origin of the earth, or
the evolution of life, there still are some mysterious things that science has
not yet fully explained. Science hardly denies or ignores mysteries -- indeed,
scientists are driven to explore nature by their fascination with mysteries.
Supernaturalists close to the edge take comfort in the resistance of
consciousness to scientific explanation, for example, and argue that only
supernaturalism can account for the mind. On this issue, we presently observe a
standoff. Supernaturalism really doesn't offer an explanation of mind, since it
doesn't explain how mind can interact with matter. Naturalism, for its part,
can only raise the hope that scientific progress will explain consciousness
someday. Still, the track-record and momentum of science is so impressive
that theologies rarely try compete so close to the edge anymore. Where can
theology retreat to?
Theology
At The Edge: According to this kind of theology, religion is
continuous with science, and tries to helpfully supplement science, because
supernatural hypotheses are necessary to explain the very existence of nature
itself and to explain the most general features of nature as a whole. The
cosmological argument and the fine-tuning argument, which we will examine soon,
stay alive at the edge by relying on science's current knowledge of the Big
Bang and the universe's fundamental laws. According to Theology At The Edge,
supernatural hypotheses should not try to compete with natural
hypotheses for explaining things within the universe. Even if the supernatural
is no longer needed to explain anything in nature, there remain dark mysteries
surrounding us when science's knowledge stops at the very edge of known nature
itself. Here at the edge, theology always seems to have the competitive
advantage, since no matter how far science goes, there will always be more
questions and more darkness. While science must admit its natural limitations,
naturalism does not have to admit defeat here at the edge. Supernaturalism
claims to hold the only remaining explanations for the universe's existence and
its overall design. However, if naturalism can expose flaws in supernaturalistic explanations while offering possible
alternative explanations, naturalism can keep its advantage. Is there anywhere
left for theology to retreat to?
Theology
Over The Edge: According to this kind of theology, religion does not
have to be reasonable or compatible with science, but just faithful. For
theology over the edge, it is entirely irrelevant whether any supernaturalistic hypotheses successfully explain anything.
Theologies Over The Edge are designed to be immune from all possible
counter-evidence, and its theologians proudly claim that their supernaturalism
cannot be proven false. Some extreme examples of Theology Over The Edge
proclaim that the best religious faith is precisely a faith in the irrational
and absurd. Theologies resting on alleged miracles or revelations are not
worried about defying rational explanation. Theology Over The Edge refuses to
accept the burden of proof and instead tries to shift the burden onto the
naturalist. “Prove me wrong,” this theology taunts naturalism, assuming that
this is the smart way to win the debate. Does theology at last have a safe
foundation here, over the edge? There is no general all-purpose argument that
the naturalist could use to prove that nothing supernatural exists. It is
impossible to search such a transcendent “space” beyond nature. No reasonable
person should claim to be certain that nothing supernatural exists. However,
the naturalist does not have to be certain that the supernatural doesn't exist
-- the naturalist simply finds that there is no good reason to believe that the
supernatural does exist. And that's enough to be a reasonable naturalist.
Debating "the evidence" with a Theology Over The Edge is pointless
and profitless, since this kind of theology doesn't have to worry about
evidence. However, a theory that cannot be refuted by any evidence enjoys no
help from any evidence. Making a theory that can't be proven false does not
make it true. Besides, there are potentially endless irrefutable theologies,
and they can't all be true, so it is far more reasonable to be skeptical
towards all of them. If naturalism can force supernatural theology not only to
the edge, but entirely over the edge, then naturalism remains standing as the
only reasonable view, and the debate between naturalism and supernaturalism is
effectively over.
So
far, we have surveyed from a great height the respective positions of
naturalism and the three kinds of supernatural theologies. In our remaining
time, we can look more closely at a few current arguments and counter-arguments
that are generating the most interest and intellectual energy from both sides.
Each argument for supernaturalism has an opposite counter-argument from
naturalism. We will begin with “The Existence of Nature” argument for
supernaturalism, and the “Megaverse”
counter-argument. Then we proceed to the “Fine-Tuning” argument for
supernaturalism, matched by the “Problem of Evil” argument. Finally, the
“Argument from Morality” favoring supernaturalism, and its counterpart
“Argument for Secular Humanism” from naturalism.
|
The “Existence of Nature” Argument for Supernaturalism 1.
Naturalism relies only on science for explanations, yet science cannot
offer hypotheses about why the natural universe exists. 2.
Naturalism cannot explain why the natural universe exists. 3. Only
supernaturalism can offer hypotheses for why the natural universe exists. Conclusion:
Supernaturalism is more reasonable than naturalism. |
This
argument depends on the point that as soon as science explains something
natural in terms of some other natural thing, science has simply enlarged our knowledge
of the natural universe, but has not explained its very existence. Suppose
science establishes the existence of some earlier universe, from which our own
universe emerged. Now nature has expanded, but its very existence has not been
explained. No matter how much more nature science discovers in the future, it
can’t explain nature’s existence itself. How should the naturalist reply to
this argument?
First, premise
3 may be true, but the conclusion does not follow from these premises. Offering
a hypothesis and offering a reasonable hypothesis are two different
things. Any supernaturalist hypothesis must actually succeed in gaining
sufficient reasonable support for itself, irrespective of the perceived
failures of naturalism.
Second, the
conclusion does not follow from these premises because this argument relies on
an additional unstated premise or two, which may be false. In this argument,
supernaturalism demands an explanation for the existence of nature. Many
theologians make this demand because they are applying a “principle of
sufficient reason” which declares that every event or entity requires a
reasonable explanation for its existence, or for the way that it is. Now,
supernaturalism offers the existence of supernatural being(s) to explain nature.
But what explains the existence of such supernatural things? Who made God?
Confronted by this question, the supernaturalist usually then abandons the
principle of sufficient reason (or modifies it to only say that every event
requires a reasonable explanation -- as God is not an event), and retreats to
the theological notion that God is precisely that being whose existence and/or
essence does not require further explaining. What sort of being is this? The
theological answer is typically that a “necessarily existing” being, whatever
that is, does not require further explaining. Even if the idea of a “necessary
being” could be made clear (dubious in itself, since we encounter no such being
in ordinary experience), and even if rational argumentation could prove the
existence of a “necessary being” (even more dubious, as the history of such
arguments embarrassingly displays), we can still wonder whether such a necessary
being would have to be a supernatural being. In other words, the
naturalist might admit that only a necessary being could supply an ultimate
explanation for everything, and then the naturalist can go on to hypothesize
that this necessary being is in fact the entire natural reality. On this
naturalist hypothesis that nature is necessary, the big-bang start to our
universe was NOT the beginning of all reality -- our visible universe is only
one small part of a large and possibly infinity number of multiple universes
(collectively named the “megaverse”). Many
cosmologists are taking the “megaverse” theory
seriously, and someday this hypothesis might be reasonably established by new
evidence and scientific testing.
|
The “Megaverse” Counter
Argument for Naturalism 1.
Naturalism can offer alternative hypotheses for the existence of our natural
universe. 2. The
hypothesis of the megaverse, as a necessary being,
satisfies the demand of sufficient reason. 3.
Supernaturalism is not the only option for explaining the existence of our
natural universe. Conclusion:
Supernaturalism is not more reasonable than naturalism. |
Some
supernaturalists try to block this naturalist hypothesis of the infinite megaverse by claiming that an infinitely existing megaverse violates reason. Such a natural infinity is
paradoxical and impossible because there has to be a beginning to the universe,
since nothing could really ever happen if an infinite number of preceding
events had to happen first. This objection is the “Kalam
Cosmological Argument,” and it concludes that God must have created the
universe at some point since the natural universe could not have already
existed for an infinite amount of time. The naturalist can reply that even
though conceiving an infinite amount of time is humanly impossible, the notion
of an infinite past violates no rules of mathematics or logic, and therefore an
infinitely old megaverse remains an ontological
possibility. Besides, most supernaturalists anticipate that this problem of
conceiving infinity can be turned around and aimed at their God, so theologians
usually do not want God to exist in ordinary time, but to instead exist in some
eternal time or timelessness. However, it is inconsistent and hypocritical for
the theologian to complain about the difficulty of conceiving an infinitely old
megaverse, when the sort of “timelessness” supposedly
enjoyed by God is just as difficult for humans to conceive.
Other
supernaturalists try to block the megaverse
hypothesis by arguing that the megaverse might be
infinite, yet still need explaining, because non-existence is easier for reason
to accept than existence, so the naturalist still hasn't explained why only
natural existence really exists instead of nothing at all. The naturalist can
reply that no supernaturalist has yet given a good argument why non-existence
or nothingness is easier for reason to accept than natural existence, so that
natural existence must require explanation but nothingness does not. Quite the
contrary -- since absolute nothingness is really difficult or impossible for
the human mind to conceive (what exactly would you be thinking about if you
tried?), therefore natural existence is far easier to think about. We are
evidently far better acquainted through experience with natural existence,
after all, and reason has a far easier time thinking about the relations
between existing things. The naturalist remains free to hypothesize that the megaverse is all that has existed and all that ever will
exist, and thus the naturalist does not need to explain why only the megaverse of nature exists instead of nothing at all.
In
conclusion, although the supernaturalist may rightly complain that the infinite
megaverse is mere speculation. And it is mere
speculation. However, the “Existence of Nature” argument for supernaturalism
only works if supernaturalism is the only logically possible explanation. But
it isn't, and the mere fact that the naturalist can propose the necessary
existence of the megaverse successfully blocks the
supernaturalist argument.
|
The “Fine-Tuning” Argument for
Supernaturalism 1.
If certain fundamental properties of nature (the “key life-permitting
properties”) were slightly different, life would never be possible in our
universe. 2.
If mere chance or some ultimate natural law is responsible for the
fundamental properties of nature, then the probability is quite low that the
“key life-permitting properties” would be as they are. 3.
If an all-knowing and all-powerful supernatural being is responsible for the
fundamental properties of nature, then the probability is quite high that the
“key life-permitting properties” would be as they are. Conclusion:
An all-knowing and all-powerful supernatural being controls the fundamental
properties of nature. |
How
should the naturalist reply to this argument?
First, there is
very little reason to suppose that premise 1 is true. It is true that if
certain fundamental properties of our universe (such as the electromagnetic
force's great strength compared to gravity's force, or the mass of the neutron
compared to the proton and electron) were slightly different, then the type of earthly
organic life that we presently understand would not be possible. However, for
all we know, other kinds of life could flourish under quite different
fundamental properties of nature.
Second, the
naturalist can accept premise 2 as probably correct, and view life as a lucky
accident of an uncaring universe. The naturalist can appeal to the notion of
the megaverse in order to make it easier to
understand that among the many (infinite?) diverse universes, we happen to live
in one hospitable to life, so our luckiness appears less mysterious. If so many
diverse universes have been created, the existence of a universe like ours
becomes far more probable.
Third, there is
very little reason to suppose that premise 3 is true. It has already been
pointed out that quite different forms of life may be possible, for all we
know. The theologian could refine premise three by supposing that a
supernatural being has an overriding aim to ensure the existence of forms of
life just like us. This refined supposition would need much additional argument
to support it, and such argument eventually resorts to suspiciously religious
dogmas for premises, since there is no obvious reason why a very intelligent
and powerful god would bother creating life like ours. Perhaps life is an
accidental by-product of the creation of what this god really wants. Carl Sagan
pointed out that from an objective perspective, the universe seems far better
designed for rocks. The naturalist can also point out that many sorts of gods
could equally be hypothesized as responsible for controlling the existence of
life in our universe, such as a committee of powerful but indifferent gods that
enjoy experimenting with life, or a god that is quite evil. In any case, there
is no need for the supernaturalist hypothesis to explain a universe that
happens to support life. The naturalist can simply return to the notion of the megaverse. If so many diverse universes have been created,
the existence of a universe like ours becomes highly probable, so that the
“Fine-Tuning Argument” fails to be compelling.
Furthermore,
this natural universe is actually quite inhospitable to life as we know it,
since locations favoring organic life seem to be very rare. We tenuously cling
to existence on the surface of an unpredictable planet lost among countless
solar systems where earth-like planets seem scarce. Perhaps there is a good
deal of life scattered across the galaxies. Yet our universe is not designed
for long-term habitation, since it will either eventually surrender to gravity
and collapse back into a “Big Crunch,” or it will expand forever into a thin
soup of useless energy that compels life to succumb to the law of entropy. It
is not hard to imagine a far more hospitable universe for life, and we can
easily imagine a better life for us, which in turn raises the problem of evil.
|
The “Problem of Evil” Counter Argument for
Naturalism 1. If
God exists, then God would not permit too many evils in the world. 2. Too
many evils exist in the world. 3.
Naturalism more easily explains so many evils in the world. Conclusion:
God probably does not exist. |
This
“Too Many Evils” argument asks whether the universe's design can reasonably
suggest the existence of a good, powerful, and intelligent god. After all, any
bad flaws in the design must be attributed to the designer, even if the
supernaturalist prefers to emphasize good aspects of creation. Naturalism is at
least as plausible as supernaturalism for explaining the world's design, since
naturalism has little difficulty accounting for both the good and bad aspects
to nature. Only a perfect design can establish the existence of a perfect
creator -- lots of little evils can quickly add up to a less-than-perfect god.
The
theologian must try to explain how God's grand good plan for this world must
require so many evils, since we can easily imagine worlds with fewer evils. The
theologian must explain why the evils in the world are just the right amount of
evil, such that no lesser amount of evils would have been sufficient to carry
out the divine plan instead. This effort to justify such an explanation why
this world is the “best of all possible worlds” is called “theodicy.” If the
theologian cannot make this theodicy explanation plausible, then monotheism is
exposed as a religion grounded on mere blind faith. Furthermore, there is a
grave danger to supernaturalism even if a theodicy succeeds. Suppose a
religious person can be confident that God has sufficient reason to permit all
evils. The danger is that evil and good begin blur together. Consider: the
theologian is saying that God has sufficient reason to permit everything
that happens in the grand design -- no event happens without God's approving
permission. What about human sins which cause great suffering (Hitler's evil
decisions, for example)? The theologian can reply that God either (a) permits
human free will to make evil decisions, for the greater good of people having
free will (so they can freely choose God, for example); or (b) God directly
causes Hitler's actions so that God controls all events for the grand design.
On this theological dilemma, either letting people sin is no big evil, or
controlling people's sin is no great evil. If sinning is no big evil, or God's
sinning is no big evil, what then is the big difference between good and evil,
from our limited human perspective? The moral argument for God (which we will
discuss next) claims that we know absolute moral truths about good and evil, so
we need to postulate God. But if God is ultimately responsible for all sin, our
capacity to figure out any big difference between good and evil is radically
undermined. Now the theologian is now trapped in a trilemma:
either no one knows what really is good or evil, or God authorizes evil, or God
performs evil. All three options lead to this conclusion: humans cannot really
know what God believes is truly moral, so no moral argument for God can work.
|
The “Morality” Argument for
Supernaturalism 1.
There are moral truths that are absolute: both universal (true for everyone)
and eternal (must always be true). 2.
For any moral truth, there must exist something that is responsible for
making that moral truth true. 3.
Nothing in the natural world, such as human beings, human societies, human
life on earth, or the wider universe can be responsible for absolute moral
truths. Conclusion:
The truth of absolute moral rules requires a supernatural reality to explain
their truth. |
How
should the naturalist reply to this argument? Premise 3 is probably true
because there is nothing permanent about human beings (their bodies and minds
keep changing) or human societies (they gradually change their moral standards
over time) or human life on earth (survival strategies of the human species
gradually change over time) or wider nature (which is always changing). Since
it is very difficult to see how something that can change can be responsible
for something universal and eternal, this argument suggests that we have to
look beyond humans, human societies, and nature itself to explain absolute
moral truths.
Naturalists
usually do not believe in the existence of absolute moral truths, holding that
their existence has not been sufficiently established by either experience,
reason, or science. Many religious people very much want to believe that there
are absolute moral truths, and do believe in them, and feel afraid of a world
in which many people don’t, but these facts about people cannot prove the
existence of absolute moral truths. Furthermore, finding any substantive moral
rule that most religious people believe, or even a substantive moral rule that
most people in the same religion really believe and consistently live by, is a
very difficult task. Consider how all religions have modified their moral rules
over the centuries, and how they have all broken apart into sects and
denominations when they cannot agree on serious moral principles. Religion is a
poor place to go looking for allegedly universal and eternal moral truths. Can
naturalism offer an alternative account of moral truths?
The
most plausible sort of naturalistic account of human morality is humanist
ethics.
|
The “Humanist Ethics” Counter Argument for Naturalism 1.
Morality is a type of practical reliable knowledge for growing and
maintaining communities. 2. As
communities interact and intersect, a humanist ethics of toleration and
respect is the wisest way to manage conflict. 3.
Humanist ethics explains why communities use diverse yet objectively true
moralities, and explains why moralities should be changed for better managing
conflict. Conclusion:
The objective truths of morality can be best explained by naturalism. |
There
is a simple naturalistic explanation for the capacity of cultural/religious
traditions to contain wisdom about what makes a good life and various practical
moralities. Morality is essentially social in nature: morality is a type of
practical reliable knowledge that aids the purpose of growing and maintaining
social relationships in communities. Morality is therefore a kind of
objective knowledge: moral rules do not subjectively depend on what any single
person happens to think. But no morality is absolutely independent of humanity
entirely, either. A community's moral truths are objectively valid, in the same
way that a country's laws are objectively valid. Moral truths are not absolute
because they can be changed by communities. Moral truths should be changed when
ethical thinking concludes that they should be changed.
Ethics
was born as intelligent thinkers pondered how people could better manage
cooperative social relationships within communities, and across social and
cultural boundaries. Humanist Ethics seeks ethical principles acceptable to all
humanity regardless of their cultural beliefs, starting from the realization
that each culture and society is a minority viewpoint when contrasted with the
rest of the world's cultures. Minorities first and foremost desire protection
from majorities, so minorities want the moral right to their own convictions
and lifestyle without social penalty, and the political right to live in peace
without government penalty. Humanist Ethics therefore mostly consists of
principles designed to promote “live and let live” moralities, and humanist
ethics is a kind of moral relativism. However, Humanist Ethics is not an ethical
relativism, since the point of any ethics is to rationally defend one system of
ethical principles for all humanity. The principles of Humanist Ethics permit
many moralities to flourish so long as they all peacefully tolerate each other.
Finally, Humanist Ethics supplies the foundation for progressive democracy.
Naturalism
is often opposed by religions because religions typically claim that only they
can understand and provide morality. Many naturalists have moral beliefs that
agree with some religions, although naturalists deny that morality depends on
the supernatural. Naturalists instead seek an understanding of morality
and try to offer improvements to morality using experience, reason, and
science. Naturalism is a worldview that accepts science's best understanding of
human nature and our ability to form orderly and peaceful societies. Naturalism
therefore has implications for politics as well as morality.
Lecture Four:
Varieties of Naturalism
Naturalism
has been opposed by rival philosophies since its earliest days, as well as by
supernatural religions. Rival philosophies most effectively oppose naturalism
by arguing that naturalism can only provide an incomplete and partial
understanding of reality. Naturalism is based on experience, reason, and
science. Therefore, rival philosophies, such as platonisms,
transcendentalisms, supernaturalisms, dualisms, idealisms, and positivisms,
offer their most effective criticisms of naturalism by arguing that naturalism
cannot provide the best understanding of experience, reason, or science. If
naturalism needs outside assistance with fully understanding its own
foundations, then naturalism is evidently incomplete and false. The naturalist
therefore argues that no non-natural assistance is needed.
Varieties
of naturalism offer different ways of handling these potential problems for
naturalism. For example, the type of naturalism known as Eliminative
Materialism simply takes the position that mental experience requires no
naturalistic explanation since those experiences actually do not exist. Other
types of naturalism, including Pragmatic Naturalism, are designed to
accommodate experience, normativity, and necessity. All naturalisms attempt to
answer the third objection by defending science and its knowledge, but this
defense can take a variety of forms, resulting in still more kinds of
naturalisms. To learn about all the varieties of naturalism, you can proceed to
the next section on Naturalism and Science.
Naturalism
and Science
Naturalism
is a worldview that relies upon experience, reason, and science
to develop an understanding of reality and humanity's place within reality.
Naturalism is hence a worldview that is heavily dependent on science for
knowledge about reality. One's attitude towards science and scientific Method
will therefore control how one thinks about naturalism.
Nowadays
two versions of naturalism are frequently contrasted: methodological naturalism
and ontological naturalism. Definitions of these two versions usually sound
like this. Methodological naturalism holds that the only sort of
knowledge available to us is the knowledge learned by applying the scientific
method to all hypotheses. On this view, the scientific method itself suffices
to weed out non-natural hypotheses as unscientific, by requiring hypotheses to
be consistent with suitably naturalistic principles (no mysterious causes, no
miracles, no violation of causal closure or conservation of energy, etc.). Such
requirements, while guaranteeing the screening out on the non-natural,
presupposes some basic understanding of what the natural consists of. Where
could that understanding come from? Only from some already established
knowledge about nature. This leads the naturalist to Ontological Naturalism,
which holds that reality only consists of those things recognized by an
exemplary science, such as physics, which has been satisfactorily tested by
scientific method. Have you noticed yet that methodological and ontological
naturalism depend on each other for substantive content? They cannot be defined
independently of each other, since methodology by itself will consider any
hypothesis for testing without prejudice, and ontology by itself is sheer
dogmatism without a standard of knowledge. The putative contrast between
methodological naturalism and ontological naturalism is spurious -- they
work together or not at all. They can have a virtuous relationship by
mutually enlarging each other as science progresses -- new scientific knowledge
often arrives with improved methodology, which in turn extends the reach of
scientific inquiry, which leads to more new knowledge, etc. You can read more
about methodological and ontological naturalism in the article "Naturalism".
The label
of Metaphysical Naturalism is sometimes applies to the broadest
definition of naturalism (see for example wikipedia's
"Metaphysical
Naturalism"). Furthermore, the labels of Physicalism and Materialism
are sometimes used by philosophers as synonyms for naturalism (you can read
about "Physicalism"
here). However, only some varieties of naturalism rely only on physics or the
notion of matter, and naturalisms frequently have contentious relationships
with metaphysics, so it is best to let Philosophical Naturalism stand
for the broadest statement of naturalism.
Accordingly
we shall persist with the definition of philosophical naturalism given here,
which combines a methodological and ontological component: "Naturalism is
a worldview that relies upon experience, reason, and science to develop
an understanding of reality and humanity's place within reality."
Now that
the genus of naturalism has been defined, what are the dominant species? We
will proceed through five stages of discriminating significant kinds of
naturalism. The conclusion of these stages identifies the seven viable
varieties of naturalism.
Stage One:
Science, Knowledge, and Reality
There are
six primary options when considering whether science yields knowledge about
reality:
Each of
these six options present pathways to many different worldviews. Options 4,
5, and 6 lead to varieties of naturalism. To become a worldview, each
option must provide a justification for preferring it over the rest. Examples
of such justifications are added below:
Options 4,
5, and 6 can lead towards varieties of naturalism, but unless option 3B
Scientific Anti-Realismis ruled out, naturalism
remains hypothetical. You can proceed to another website on Scientific Realism.
Only three
of the 6 primary worldviews can lead to kinds of naturalism. They are:
4. Science
is able to give increasingly reliable knowledge about reality. There may
be other ways besides science for knowing reality, but those ways are not
better than science. One variety can be a kind of naturalism: 4B. Synoptic
Monism (one kind of ultimate reality that is knowable in different ways).
5. Science
is the only source of knowledge about reality. The only type of knowledge is
scientific knowledge. However, some of reality consists of entities that cannot
be known by science, simply because science is not designed to provide
knowledge about these entities. Two interesting varieties: 5A. Perspectival
Realism (experience is a perspective on reality but not itself knowable),
and 5B. Transcendent Realism (some natural reality forever escapes
science).
6. Reality
only consists of what science knows about. Only what can be known by science
really exists. Two interesting varieties: 6A. Current Scientific Exclusivism
(reality only consists of what current science knows now), and 6B.
Scientific Exclusivism (reality only consists of what perfected science
would know).
Each of
these three major worldviews about science leads to three significant kinds of
naturalism: Synoptic Monism, Perspectival Realism, and Scientific Exclusivism.
Transcendent realism may be ignored here because any transcendent natural
reality, if it exists, cannot be the subject of the contest between naturalism
and non-naturalism. Current scientific exclusivism may also be ignored here
because the scientific exclusivist, when challenged over something that current
science can't yet explain, will resort to the claim that future science will explain
it.
Stage Two:
Explaining Experiences using Science's Theories
Let us
further consider ways of distinguishing kinds of naturalism. Consider these
three kinds of naturalisms.
Narrow
Naturalism:
If some X is among those things (or among the properties of those things) which
are described by science's best theories, then the existence of X is accepted;
otherwise, its existence must be denied.
Fitting
Naturalism:
All the entities accepted by narrow naturalism exist, plus additional things as
follows: If some X is successfully hypothesized as really being a Y that is
among those things (or among the properties of those things) which are
described by science's best theories, then the existence of X may be accepted.
Broad
Naturalism:
All the entities accepted by fitting naturalism exist, plus additional things
as follows: If some X is successfully explained by a hypothesis about why X
exists which references only those things (or properties of those things) which
are described by science's best theories, then the existence of X may be
accepted.
It must be
made clear that in these definitions, we mean by "those things" any
entities which are used by scientific theories -- from "things" in
the substantive sense of material bodies, and also energies, forces, laws, and
the like. Naturalists can disagree among themselves about the types of entities
that are attributed existence by scientific theories (for example, do laws of
nature really exist in the same way that atoms exist, or do numbers exist
because science uses measured quantities, etc.). These disagreements are not
relevant to the categorization of naturalisms discussed here.
Let's
apply the distinction between these three naturalisms to the experience of
colors. The narrow naturalist is tempted to reject the existence of colors,
because no color is found among the basic properties of those things described
by science's best theories. If the narrow naturalist is narrow in an additional
sense because she considers physics as supplying the best scientific theories,
then this naturalist will reject the existence of colors because color is not a
property of any atomic or subatomic particle, or of any force of
nature. The fitting naturalist can accept the existence of colors if an
adequate hypothesis find a fitting place in nature for colors. For example, a
successful hypothesis that a color really is the "surface spectral
reflectance" from an object would permit the fitting naturalist to accept
that colors naturally exist. The broad naturalist only asks that some adequate
hypothesis, which uses terms from science's best theories, explains why colors
are experienced. For example, a successful hypothesis that explains how colors
are seen whenever sufficient visible light in certain wavelengths stimulates
the optic systems of normally functioning human brains would permit the broad
naturalist to accept that colors naturally exist. In summary, the narrow
naturalist wants to eliminate colors from nature by comparing them
against science's theories, the fitting naturalist wants to fit colors
into the natural world by reducing them to scientific things, and the broad
naturalist wants liberal flexibility to accept colors by explaining how
colors are naturally experienced.
So far we
have distinguished six kinds of naturalism, along two dimensions: (1) the
degree of ontological confidence given to science, from Synoptic monism to
perspectival realism to scientific exclusivism; and (2) the breadth of
explanatory discretion given to science, from narrow to fitting to broad naturalism.
Stage
Three: How Many Sciences Describe Reality?
There is
one more dimension that further distinguishes kinds of naturalisms: (3) the
number of scientific fields permitted to describe reality. Some naturalists are
happy with letting many sciences know reality, while other naturalists want
only one scientific field to know reality. The latter type of naturalists have
typically accepted a methodological principle that may be called "reductionist
universalism" -- only the smallest parts of reality really exist, and
the natural laws about those parts are universally valid (they hold in all
regions of the universe), exclusively valid (no other laws have independent
validity), and exhaustively valid (all events are dictated by these laws). As
physics is the scientific field that knows the smallest parts of reality,
reductionist universalism amounts to the claim that all of reality ultimately
consists solely of subatomic particles and that all events in the natural
universe are ultimately dictated by the laws those subatomic particles obey.
The program of reductionism amounts to the claim that any complex thing should
be analyzed down into its components, and each of these components must in turn
be analyzed further, etc., until the ultimate smallest parts (those studies by
subatomic physics) are identified and their interact laws are discovered.
Theoretical reductions to physics are therefore a series of analyses, from
higher complex levels of nature to lower simple levels of nature, until the
lowest (smallest) level is reached, and this series of analyses explains how
the behavior of any complex thing is fully explained by the interactive
behaviors of the smallest parts. If, according to reductionist universalism,
subatomic particles have ontological priority and their laws have explanatory
priority, then physics has naturalistic priority. The sciences could be unified
in this way into physics alone. You can read more about the history of "Atomism",
"Reduction",
and the "Unity
of Science" movement. The naturalist who follows reductionist
universalism will be the sort of materialist who puts physics first -- this
naturalism is "physicalism."
Other
kinds of naturalism do not agree with reductionist universalism and feel
comfortable with permitting other scientific fields to describe reality with
just as much legitimacy as physics. Because the biological and social sciences
have traditionally used some methodological principles and modes of causality
that depart from the physical sciences, many naturalists want to draw a line
between trustworthy physical sciences (physics, chemistry, geosciences,
astronomy, cosmology) and suspicious biological and social sciences. For
example, some approaches to the social sciences have assumed the existence of
social entities (that must not be treated as mere aggregates of people), and
some biological and social sciences have use teleological causality
(explanations that appeal to future outcomes to explain present behaviors). We
will not discuss this internal dispute among naturalists here. However, the
naturalists who would permit just the physical sciences to describe reality
(let us call their view "scientism") do form a separate camp from
those naturalists who are comfortable with all of the physical, biological, and
social sciences describing reality (let us call their view "pluralism").
Stage
Four: How Many Naturalisms?
The
varieties of naturalism may be distinguished along three dimensions: (1) the
degree of ontological confidence given to science, from Synoptic monism to
perspectival realism to scientific exclusivism; (2) the breadth of explanatory
discretion given to science, from narrow to fitting to broad naturalism; and
(3) the number of scientific fields permitted to describe reality, from just
physics to the physical sciences to all sciences.
If all
combinations of these nine kinds of naturalism were created, then 27 varieties
of naturalism would result. However, many of these 27 varieties are not viable
because of coherence problems, and some are not practical because their
principles would conflict. There are only seven viable varieties of Naturalism.
Stage
Five: The Seven Viable Varieties of Naturalism
These
seven viable varieties of naturalism are distinguished from each other
according to their views on (1) the degree of ontological confidence given to
science, from synoptic monism to perspectival realism to scientific
exclusivism; (2) the breadth of explanatory discretion given to science, from
narrow to fitting to broad naturalism; and (3) the number of scientific fields
permitted to describe reality, from just physics to the physical sciences to
all sciences. The seven varieties are listed in order from the very restrictive
to the very open assertions about what reality is like.
1. Eliminative
Physicalism: reality only is what physics says. This variety is the most austere
and rigid naturalism, restricting reality most sharply. According to
Eliminative Physicalism, the only realities are those that number among those
things (or among their properties) which are described by physics’ best
theories. This eliminativism typically accepts the principle of “reductionist
universalism.” Once eliminativism rejects the existence of some X, then any
belief or judgment or knowledge claim about X is strictly false or quite
meaningless. Trouble soon erupts, because the other physical sciences, such as
chemistry, do not regard their respective claims about nature as meaningless
and may not agree that reductionism will ever work. Sometimes eliminative
physicalists relent from this harsh treatment of eliminable entities, saying
that discourse about many condemned Xs can still be partially and temporarily
meaningful (at least until replaced with physicalist discourse), and
“second-class” practical language and knowledge about these Xs may be needed.
For example, naturalistic philosophy of mind can treat folk psychology as not
entirely false since its talk of perceptions and other mental things may at
least point to real phenomena that require better description rather than no
description. For example, Paul Churchland’s
endorsement of eliminative materialism treats the ontology of perceptions and
beliefs as “illusion” yet his own cognitive science admits the existence of the
“qualitative character of a sensation” in the course of explaining it.
Successful explanations, even of the most austere reductive sort, tend to
confirm the reality of the things explained (failed explanations
arouse doubt). Genes are not unreal because they are composed of nucleotide molecules. The Eliminative
Physicalist who is too generous with “second-class” language and knowledge,
especially regarding mental affairs, risks sliding over to Exclusivist Liberal
Pluralism, and is under great pressure to at least admit the superiority of
Reductive Physicalism.
2. Reductive
Physicalism: reality must be reducible to physics. This variety is almost
as austere as eliminative physicalism. According to Reductive Physicalism, the
only realities are those of physics’ best theories, plus those additional
things which can be theoretically and ontologically reduced to them. Reductive
Physicalism accepts reductionist universalism, but resists collapsing into
eliminative physicalism by permitting the existence of things that can have
their own properties, behaviors, and laws that physics itself does not
investigate. Most eliminativists gain their confidence in the non-existence of
X after reductivists have done their work, and most physicalists are
eliminativists about some things (the paranormal, the mythical) and
reductivists about other things (the biological, the social). Reductive
Physicalism must demand complete submission to the principle of reductionist
universalism from all other sciences, or else it must admit the superiority of
Exclusivist Liberal Pluralism. The practical difference between a reductivist
and an eliminativist is that an eliminativist about some X would not seek any
reductive explanation of X, since it is irrational to attempt to explain the
non-existent. However, most eliminativists gain their confidence in the
non-existence of X after reductivists have done their work, and most
physicalists are eliminativists about some things (the paranormal, the
mythical) and reductivists about other things (the biological, the social).
Challenges to reductionism can arise from the natural sciences, such as biology
or geology – the reductive physicalist demands that these sciences’ entities
and laws be reducible in principle to those of physics, but no one knows how to
even attempt such a reduction. In light of such troubles among the physical
sciences, the social scientist, not surprisingly, is tempted to rebel against
this imperial demand of physics. Resistance to reductive universalism among
social scientists is not necessarily matched by enthusiasm for theoretical
pluralism in their own fields, however; a separate defense of theoretical
pluralism is needed. Psychology in particular must deal with the first-person
situated and subjective perspective of consciousness, and many philosophers
also want to preserve legitimate discourse and inquiry into such experience. Churchland may be better located here with Reductive
Physicalism, along with Jaegwon Kim who admits that
some mental features may not be entirely eliminable as unreal by proven
reductions.
3. Exclusivist
Liberal Physicalism: physics alone supplies explanations of all reality.
This variety is attractive to naturalists who are skeptical about reductive
explanations of all realities to physical realities. Exclusivist Liberal
Physicalism holds that reality consists of what can be explained by physics.
This variety of naturalism does not adhere to the principle of reductionist
universalism, keeping it distinct from its eliminativist and reductivist
cousins. Exclusivist Liberal Physicalism does maintain an analogue of
reductionist universalism, which can be called “explanatory universalism,”
which instead declares that only the things and laws theorized by physics may
be referenced when fully explaining reality, so that explanations of things are
best given solely in terms of the things recognized by physics alone, if only
by some future final physics. This prioritization of physical explanation is
frequently signaled by hostility towards consciousness, free will, social
forces, or anything that could challenge strict determinism. Ernest Nagel’s
naturalism might be best classified here; his hostility towards life and social
science explanations using suspicious teleologies was
matched by his confidence in his “bridge-laws” for reducing such “explanations”
to those of physics. These “bridges” are multiply-realizable and must endlessly
proliferate, however. The primary difficulty that confronts Exclusivist Liberal
Physicalism is causality: physically explainable but irreducible things can
appear to have their own causally lawful relationships, and so one event might
be described as having two sufficient causes, or the very notion of “cause” can
fracture into distinct senses. The work of Wilfrid Sellars and Daniel Dennett make strenuous efforts to
reconcile the normative, manifest, and folk ways of living and speaking with
physicalism’s underlying truth. By denying complete reductionism in practice, Sellars and Dennett can sound like pluralists or even perspectivalists, but their firm commitment to the
exclusive ontological reality of the strictly physical ultimately belies their
generosity towards normative, intentional, and psychological modes of language.
Unless the descriptive and causal overdetermination issues are eventually
resolved, however, Exclusivist Liberal Physicalism is under great pressure to
either collapse into Reductive Physicalism, or to go in the opposite direction
and mutate towards Perspectival Pluralism.
4. Exclusivist
Liberal Scientism: the physical sciences supply explanations of all
reality. For reasons given below, this position is better labeled as Non-Reductive
Physicalism. Like any middle position that tries to compromise all things, this
variety is highly unstable, under intense pressure to resign the field in favor
of its exclusivist cousins. According to this position, reality consists only
of those things that are explainable by the physical sciences. But why just the
physical sciences? The Exclusivist Liberal Physicalist will complain that
purely physical explanations must in principle prevail across all the physical
sciences anyways. The Exclusivist Liberal Pluralist will complain that
admitting the explanatory power of the physical sciences should be extended to
all of the sciences. Even worse than competition from its cousins, this variety
suffers from both of the severe difficulties confronting its cousins. Like
Exclusivist Liberal Physicalism, this variety must resolve the issue of causal
overdetermination, lest it admit the superiority of Reductive Physicalism. Like
its other cousin, Exclusivist Liberal Pluralism, this variety must also resolve
the issue of incoherence between the physical sciences, which can be handled
more easily by Reductive Physicalism on the one hand, or by Perspectival
Pluralism on the other. During the 20th century, the two most popular forms of
Exclusivist Liberal Scientism were Non-reductive Physicalism and the closely
related position of Emergent Supervenient Naturalism. For Non-Reductive
Physicalism, the only realities are those of physics’ best theories, plus those
additional things of the other physical sciences which can be theoretically
reduced to them, plus those non-reducible experiential / mental / social
properties or powers which are ontologically dependent on physical things. This
position is widely labeled as “Non-reductive Naturalism” but that label is too broad,
obscuring the remaining varieties of naturalism (types 5, 6, 7) and omitting
its distinctive prioritization of physics. For this position, the most urgent
priority in the defense of naturalism is ontological: mental properties are
distinguishable from, but still entirely dependent on, physical things. Dynamic
and causal supervenience holds globally. Non-reductive physicalists sometimes
express this position in terms of Emergent Naturalism: reality includes many
entities which are emergent (neither explanatorily nor ontologically reducible
to physics) even though these entities entirely supervene on (cannot exist
without) realities known by perfected physics. Emergent Naturalism has
enthusiasm for the supervenience strategy, and would not obstruct the search
for correlation, dynamic, and causal superveniences. Dubious whether the
supervenience strategy will ever culminate in satisfactory reductions of all
phenomenal/mental entities, the option of emergence can seem attractive. There
are no non-physical things, yet there are non-physical “mental” properties that
can be experienced, even though they must really be properties of physical
things. Even if other sciences besides physics experimentally confirm theories
about “mental” things as having somewhat independent existences and/or causal
powers from physical things, such knowledge is inferior to physics, and any
suggested quasi-independence of the mental from the physical is only illusory.
To summarize, this Non-Reductive Physicalism is the compromise position taken
by a philosopher who admires the reductivist program and endorses physicalism,
yet also believes that some experiential/ biological/social properties will
likely forever resist theoretical reduction. W. V. Quine’s
holistic scientism is probably best categorized here, and his philosophy
spawned a wide variety of non-reductive naturalisms projecting at least a
“token-token” identity if not “type-type” identity of mind and matter. Although
Quine was notoriously hostile towards mental states,
he was not a straightforward reductive physicalist, by endorsing the knowledge
of the several natural sciences while demanding strict supervenience over
micro-physical matters. Donald Davidson’s Anomalous Monism is in this
non-reductive tradition, along with many similar formulations. Non-Reductive
Physicalism is inherently unstable, because any devout endorsement of
physicalism is embarrassingly compromised by the admission that some
phenomenal/mental entities will never be reduced: not by any semantic, epistemic,
explanatory, scientific, functional, or ontological means. Non-reductive
physicalists are torn by this position’s conflicting pressures. A genuine
physicalist should instead bravely vow that future science will supply all
necessary reductions, while a stubborn non-reductivist should instead slide
over to Emergent Supervenient Naturalism (which in turn is under pressure to
mutate towards Perspectival Pluralism) or Exclusivist Liberal Pluralism (which
is similarly under pressure to mutate into Perspectival Pluralism).
5. Exclusivist
Liberal Pluralism: the many sciences supply explanations of all reality.
This variety is attractive to naturalists who are skeptical about reducing all
realities to physical realities on the one hand, and also skeptical about any
naturalistic ontology that permits experience to yield genuine perspectives on
reality that can never be fully explained by the sciences. Exclusivist Liberal
Pluralism holds that reality consists of what can be explained by the many
sciences including the life sciences and social sciences. Its pluralism
encourages all of the sciences to draw their own conclusions about reality. But
this liberality also encourages such a diversity of conclusions about reality,
and such a multiplicity of entities for theorizing, that incoherence among them
will inevitably result. The only way to manage this diversity is to assign each
science its own task of exploring a “level” or “aspect” of reality, so that
clashing scientific theories are kept apart. For example, chemistry studies the
laws peculiar to interacting molecules, while subatomic physics studies the
quite different laws peculiar to subatomic particles, without worrying how
these entities and laws specifically relate to each other. The naturalistic
pluralist must accept the “disunity of science” and defend each science’s
theoretical autonomy for deciding how to best satisfy the methodological
standards of empirical inquiry. Exclusivist Liberal Pluralism is also burdened
with showing how all of experience and the mental life is in principle
explainable by the many sciences. The first-person situated and subjective
perspective of consciousness must be ultimately explainable in terms of the
third-person objective knowledge of the sciences. Taking up the eliminativist
challenge to empirically justify talk of intentions, beliefs, and the like, a
philosopher of mind can not merely praise the utility the “intentional stance”
but also thereby justify it over reductionist accounts as well. This liberal
pluralism can proclaim its advantages over all pretenses to physicalist
reductionism, but its dealings with experience remain extremely hazardous. Any
experiences not satisfactorily explained by the sciences will pressure this
naturalism to mutate into Perspectival Pluralism. Barry Stroud, recognizing the
position of Exclusivist Liberal Pluralism and labeling it as “open-minded or
expansive naturalism,” prefers it over all reductionisms. However, Stroud warns
that excessive expansiveness, a willingness to undertake explanations for most
everything we encounter, may remove substantive meaning from the term
“naturalism.” John Searle’s “biological naturalism” is caught up in this
problem too, when he simultaneously insists that the life sciences can deal
with subjective consciousness in a way that mere physicalism or machine
functionalism will never succeed. However, Searle’s strong insistence on the
separate ontological category of subjectivity makes one wonder if even the life
sciences or psychological/social sciences could ever handle such subjectivity,
making his stance sound much more like Perspectival Pluralism or even Synoptic
Pluralism.
6. Perspectival
Pluralism: the many sciences along with experience indicate plural
perspectives on reality. This variety offers a middle path between Exclusivist
Liberal Pluralism’s reliance on science alone and Synoptic Pluralism’s
hypostatizations of ways of experiencing and knowing reality. Perspectival
Pluralism concludes that the sciences are unable to fully explain experience
and the mind, yet it also respects how the sciences can cohere with, and
frequently illuminate, much of experience and the mind. Perspectival Pluralism
finds that experience and scientific knowledge presents multiple perspectives
upon the same reality. The first-person situated and subjective perspective of
consciousness is neither inexplicable nor incongruent with the third-person
objective knowledge of the sciences, since all experience and knowledge is
embedded in situated contexts. Our mental lives are correlated to some degree
with nervous processes, scientific knowledge grows from our careful
observations of the world, and our experiences of the world can be usefully
coordinated with scientific knowledge. Appreciation for the many vital and
practical relationships and interpenetrations among experiences and scientific
knowledge inspires the Perspectival Pluralist to postulate one natural world
which experience and science both reveal. Pleas for perspectivalism and
pluralism resound throughout the works of pragmatists, including John Dewey, a
paradigmatic example of a perspectival pluralist. Nicholas Rescher applies the
label of “perspectival pluralism” for his metaphilosophical stance in addition
to “pragmatic idealism.” Ronald Giere also calls his position “perspectival
pluralism” and in recent writings he has acknowledged his connection with
pragmatism. Pragmatic pluralists understandably express high confidence in
science’s ability to find explanations for all phenomena, since they oppose the
positivisms, constructivisms, and antirealisms which lead away from naturalism.
Such confidence is actually the defining characteristic of Exclusivist Liberal
Pluralism, which means by “explanation” something stronger that the weak
coordination between science and experience sought by Perspectival Pluralism.
For example, a Exclusivist Liberal Pluralist will anticipate that
neurophysiology may someday “explain” human emotions in a near-reductionist
manner (romantic love is “caused” by certain neurotransmitters,
for example). The Perspectival Pluralist resists such narrow causality,
preferring to emphasize how science can help understand the plurality of
interrelationships between social conduct, personal feelings, and brain
modifications. The Perspectival Pluralist must tread carefully when explaining
science’s “explanations” of experience and the mental life. To justify
confidence in one natural reality, the Perspectival Pluralist develops an
ontological system to show how all experience and all scientific knowledge can
be coordinated together. Any irreconcilable contradiction between some aspect
of experience "E" and some part of scientific knowledge
"K", a contradiction so severe that it is impossible to see how E and
K could both be about the same natural reality, dooms Perspectival Pluralism.
Making this task easier is the view held by Perspectival Pluralism (but not
Synoptic Pluralism) that experience is not itself a kind of knowledge that
could challenge scientific knowledge. Synoptic Pluralism is designed to handle
conflicts between experiential knowledge and scientific knowledge by assigning
what each knows to sharply dichotomized modes of reality. The Perspectival
Pluralist worries that such an accommodating synopticism is tantamount to a
resignation to ontological dualism. The disagreements between Dewey’s
perspectival pluralism and the systems of his contemporaries George Santayana
and Alfred North Whitehead (both Synoptic Pluralists) prefigure much of the
contemporary debate between naturalisms. This disagreement has more recently
erupted over Dual Aspect Monism. Can Dual Aspect Monism make any proper claim
to naturalism? David Chalmers suggests that ample psychophysical laws ensure a
fundamental ontological connection between mind and matter, holding out hope
for naturalism’s victory over ontological dualism in a manner suggestive of
Perspectival Pluralism. Psychophysical laws only raise the problem of causal
overdetermination once again. Pragmatic pluralists such as Hilary Putnam and
John Dupré find that multiple modes of explanation
generate multiple modes of causality. Can a vision of multiple modes of one
reality be adequately distinguished from a straightforward ontological
pluralism of many worlds. Nelson Goodman notoriously raises doubts about
halting short of ontological pluralism.
7. Synoptic
Pluralism: the many sciences, reason, and experience indicate plural yet
related modes of reality. This variety is the most open and flexible
naturalism, defining reality most generously. According to Synoptic Pluralism,
reality has a variety of aspects or modes as known by the many sciences, and
also has aspects or modes known by experience and perhaps pure reason as well
which the sciences are incompetent to describe or explain. The simplest forms
of Synoptic Pluralism include Dual Aspect Monism (the sciences deal only with
reality’s physical aspect while the introspective mind only deals with
reality’s mental aspect), and Panpsychism (the sciences accurately but only
partially describe all realities, because the sciences cannot capture the
sentient or feeling aspect of these realities). Dual Aspect Monism has the
heavy burden of confidence that science will figure out the deepest ontological
relations between mind and matter despite the irreducible subjective/objective
dichotomy; Thomas Nagel is a recent illustration. Epiphenomenalism is another
intriguing form of Synoptic Pluralism (although the epiphenomenalist who denies
that irreducible qualities of experience are themselves objects of knowledge
would instead be a Perspectival Pluralist). Synoptic Pluralism requires some
sort of naturalistic ontology — an account of reality that constructs a
coherent understanding of one single natural reality with multiple aspects and
experienced/known in multiple ways. Synopticism can more easily segregate
incompatible aspects into distinct modes of reality that need not fully overlap
or intersect. Charles Peirce and William James prefigure much of 20th century
Synoptic Pluralism in America. Santayana’s four Realms of Being and Whitehead’s
panexperiential Process Philosophy emphasize their capacious accommodation of
diverse modes of experiencing/describing/knowing. Stephen Pepper’s World
Hypotheses, Paul Weiss’s Modes of Being, Nelson Goodman’s Ways of Worldmaking, and Richard Rorty’s
Linguistic Turn have similar merits. A synoptic naturalist ontology is not
testable by ordinary experimental methods, because it is designed to be
maximally compatible and coherent with all knowledge and experience from all
sources. Since experience increases and knowledge evolves, a naturalistic
ontology must adapt to keep pace, and this adaptability serves as its test of
adequacy. Synoptic Pluralism distinguishes itself from Perspectival Pluralism
by concretizing and hypostatizing experienced and known entities for their
classification into sharply distinct ontological categories, to forbid the
merging of these entities into coordinated perspectives upon reality. On the
other hand, unless Synoptic Pluralism can develop its own compelling
naturalistic ontology, its enthusiasm for multiple modes of reality can easily
amount to ontological dualisms and pluralisms which entirely depart from
naturalism.