Jan 13, 2012
In my book Where the Conflict Really Lies: Science, Religion and Naturalism, I argue that there is superficial conflict but deep concord between modern science and theistic religion (Christianity, Judaism, Islam), but superficial concord and deep conflict between science and naturalism.
What is that deep conflict between naturalism and science? First, I’m taking naturalism as the belief that there is no such person as God or anything like God. Others use that term in other ways; this is how I use it. Second, I take it that naturalism includes materialism with respect to human beings: If you are a naturalist, you will think that human beings are material objects. They do not have an immaterial self or soul or ego; they are made through and through of flesh and blood and bones. It is this belief—naturalism construed as including materialism—that I say is in conflict with science.
The argument is a bit too involved to state in detail here (for a full-dress presentation, see chapter 10 of the book), but I can at least give its flavor. The conflict has to do with our cognitive faculties: memory, perception, logical intuition, introspection, and so on. And the place to start is with the thought that evolution, natural selection, doesn’t give a hoot about what you believe: It rewards adaptive behavior and punishes maladaptive behavior, but is wholly indifferent to the content of your belief. It can be expected to promote neurophysiology that causes adaptive behavior, but it has no interest, as such, in reliable belief formation. And this, in conjunction with naturalism, suggests a sort of skepticism; it suggests that human cognitive faculties are not reliable, that they don’t produce an appropriate preponderance of true belief over false. If naturalism is true, and our cognitive faculties have been produced by natural selection, it seems likely that our cognitive faculties are not particularly reliable.
This thought is of course not original with me. According to Friedrich Nietzsche, for example,
It is unfair to Descartes to call his appeal to God’s credibility frivolous. Indeed, only if we assume a God who is morally our like can “truth” and the search for truth be at all something meaningful and promising of success. This God left aside, the question is permitted whether being deceived is not one of the conditions of life.
Indeed, Darwin himself expresses serious doubts along these lines:
With me the horrid doubt always arises whether the convictions of man’s mind, which has been developed from the mind of the lower animals, are of any value or at all trustworthy. Would any one trust in the convictions of a monkey’s mind, if there are any convictions in such a mind?
More explicitly, the argument begins with the idea that the probability that our cognitive faculties are reliable (produce an appropriate preponderance of true belief over false belief), given naturalism and evolution, is low. Consider a population of creatures a lot like us on some other planet (or perhaps in one of those other universes partisans of the multiverse like to invoke); if all we know about them is that naturalism holds for them, and that they and their cognitive faculties have come to be by way of natural selection, then, with respect to what we know, it is improbable that their cognitive faculties are reliable. We can put that more briefly as:
1. P(R/N&E) is low
Where R is the proposition that our cognitive faculties are reliable, N is the proposition that naturalism is true, and E is the proposition that we and our cognitive faculties have come to be by way of evolution by natural selection.
Now suppose (1) is true. Then anyone who accepts N&E, and also sees that (1) is true, has a defeater for the common sense belief or assumption that our cognitive faculties are reliable. She has a reason to reject that belief, to give it up. And if you have a defeater for the belief that your cognitive faculties are reliable, you also have a defeater for any belief produced by your cognitive faculties—which, of course, comprises all of your beliefs, including N&E itself.
But why believe (1)? What we can assume about these creatures, given that they have been produced by evolution, is that their behavior is adaptive, conducive to survival and reproduction. According to materialism, this behavior is caused by processes in their brains—the underlying neurology, as we may call it. That neurology, therefore, is also adaptive. That neurology, furthermore, also causes or determines their beliefs. But, as far as that adaptive behavior is concerned, it doesn’t matter whether those beliefs are true or false. If true, fine; if false, also fine. Either way, the underlying neurology causes adaptive behavior. It therefore doesn’t matter whether their beliefs are mostly true or mostly false.
But isn’t it just obvious that adaptive action is more likely to be caused by true beliefs than by false? If these creatures harbor mostly false beliefs, won’t they act in maladaptive ways? If they believe jumping off a cliff will improve their health, won’t they come to an early end?
Yes, of course; this is certainly how we ordinarily think. But this ordinary way of thinking doesn’t fit with materialism. Given materialism, a belief will have to be something like an event or process in someone’s nervous system. A belief will have two kinds of properties: On the one hand, it will have neurophysiological properties (call them “NP properties”) involving how this structure is connected with other neural structures, the rate of fire in various parts of the structure, and the like. But if it is a belief, it will also have to have content; it will have to be the belief that p for some proposition p. And the crucial point to see here is that it is by virtue of its NP properties, not its content, that a belief enters the causal chain that leads to behavior.
Take any belief: If it had had the same NP properties but different content, it would have caused the same behavior, made the same causal contribution to behavior. But that means that the content of belief plays no causal role with respect to behavior and hence with respect to fitness and adaptive behavior. And that means that the probability of a given belief’s being true, given N&E, will have to be about 0.5. But then the probability of reliability of the part of these creatures’ cognitive faculties will be very low.
Of course what holds for them also holds for us: P(R/N&E) for us will also be low. If it is, however, then anyone who accepts N&E and also sees that (1) is true will have a defeater for R and therefore a defeater for any belief she holds, including N&E itself. N&E is therefore self-defeating; it is a belief we can’t rationally hold. But then naturalism and evolution are in conflict—not in the sense that they are logically incompatible, but in the sense that we can’t rationally accept them both. And since E is a crucially important part of current science, there is deep conflict between naturalism and science.
Alvin Plantinga is the John A. O’Brien Professor of Philosophy at the University of Notre Dame and the author of the new book Where the Conflict Really Lies: Science, Religion and Naturalism.