EVERYTHING IS SUBJECT TO DARWINISM EXCEPT MY FAITH IN DARWINISM:

Evolution vs. Naturalism: Why they are like oil and water (Alvin Plantinga, July/August 2008, Books & Culture)

[W]hat evolution tells us (supposing it tells us the truth) is that our behavior, (perhaps more exactly the behavior of our ancestors) is adaptive; since the members of our species have survived and reproduced, the behavior of our ancestors was conducive, in their environment, to survival and reproduction. Therefore the neurophysiology that caused that behavior was also adaptive; we can sensibly suppose that it is still adaptive. What evolution tells us, therefore, is that our kind of neurophysiology promotes or causes adaptive behavior, the kind of behavior that issues in survival and reproduction.

Now this same neurophysiology, according to the materialist, also causes belief. But while evolution, natural selection, rewards adaptive behavior (rewards it with survival and reproduction) and penalizes maladaptive behavior, it doesn't, as such, care a fig about true belief. As Francis Crick, the co-discoverer of the genetic code, writes in The Astonishing Hypothesis, "Our highly developed brains, after all, were not evolved under the pressure of discovering scientific truth, but only to enable us to be clever enough to survive and leave descendents." Taking up this theme, naturalist philosopher Patricia Churchland declares that the most important thing about the human brain is that it has evolved; hence, she says, its principal function is to enable the organism to move appropriately:

Boiled down to essentials, a nervous system enables the organism to succeed in the four F's: feeding, fleeing, fighting and reproducing. The principal chore of nervous systems is to get the body parts where they should be in order that the organism may survive … . Improvements in sensorimotor control confer an evolutionary advantage: a fancier style of representing is advantageous so long as it is geared to the organism's way of life and enhances the organism's chances of survival. Truth, whatever that is, definitely takes the hindmost.

What she means is that natural selection doesn't care about the truth or falsehood of your beliefs; it cares only about adaptive behavior. Your beliefs may all be false, ridiculously false; if your behavior is adaptive, you will survive and reproduce. Consider a frog sitting on a lily pad. A fly passes by; the frog flicks out its tongue to capture it. Perhaps the neurophysiology that causes it to do so, also causes beliefs. As far as survival and reproduction is concerned, it won't matter at all what these beliefs are: if that adaptive neurophysiology causes true belief (e.g., those little black things are good to eat), fine. But if it causes false belief (e.g., if I catch the right one, I'll turn into a prince), that's fine too. Indeed, the neurophysiology in question might cause beliefs that have nothing to do with the creature's current circumstances (as in the case of our dreams); that's also fine, as long as the neurophysiology causes adaptive behavior. All that really matters, as far as survival and reproduction is concerned, is that the neurophysiology cause the right kind of behavior; whether it also causes true belief (rather than false belief) is irrelevant.

Next, to avoid interspecies chauvinism, let's not think about ourselves, but instead about a hypothetical population of creatures a lot like us, perhaps living on a distant planet. Like us, these creatures enjoy perception, memory, and reason; they form beliefs on many topics, they reason and change belief, and so on. Let's suppose, furthermore, that naturalistic evolution holds for them; that is, suppose they live in a naturalistic universe and have come to be by way of the processes postulated by contemporary evolutionary theory. What we know about these creatures, then, is that they have survived; their neurophysiology has produced adaptive behavior. But what about the truth of their beliefs? What about the reliability of their belief-producing or cognitive faculties?

What we learn from Crick and Churchland (and what is in any event obvious) is this: the fact that our hypothetical creatures have survived doesn't tell us anything at all about the truth of their beliefs or the reliability of their cognitive faculties. What it tells us is that the neurophysiology that produces those beliefs is adaptive, as is the behavior caused by that neurophysiology. But it simply doesn't matter whether the beliefs also caused by that neurophysiology are true. If they are true, excellent; but if they are false, that's fine too, provided the neurophysiology produces adaptive behavior.

So consider any particular belief on the part of one of those creatures: what is the probability that it is true? Well, what we know is that the belief in question was produced by adaptive neurophysiology, neurophysiology that produces adaptive behavior. But as we've seen, that gives us no reason to think the belief true (and none to think it false). We must suppose, therefore, that the belief in question is about as likely to be false as to be true; the probability of any particular belief's being true is in the neighborhood of 1/2. But then it is massively unlikely that the cognitive faculties of these creatures produce the preponderance of true beliefs over false required by reliability. If I have 1,000 independent beliefs, for example, and the probability of any particular belief's being true is 1/2, then the probability that 3/4 or more of these beliefs are true (certainly a modest enough requirement for reliability) will be less than 10-58. And even if I am running a modest epistemic establishment of only 100 beliefs, the probability that 3/4 of them are true, given that the probability of any one's being true is 1/2, is very low, something like .000001.7 So the chances that these creatures' true beliefs substantially outnumber their false beliefs (even in a particular area) are small. The conclusion to be drawn is that it is exceedingly unlikely that their cognitive faculties are reliable.

But of course this same argument will also hold for us. If evolutionary naturalism is true, then the probability that our cognitive faculties are reliable is also very low. And that means that one who accepts evolutionary naturalism has a defeater for the belief that her cognitive faculties are reliable: a reason for giving up that belief, for rejecting it, for no longer holding it. If there isn't a defeater for that defeater—a defeater-defeater, we could say—she can't rationally believe that her cognitive faculties are reliable. No doubt she can't help believing that they are; no doubt she will in fact continue to believe it; but that belief will be irrational. And if she has a defeater for the reliability of her cognitive faculties, she also has a defeater for any belief she takes to be produced by those faculties—which, of course, is all of her beliefs. If she can't trust her cognitive faculties, she has a reason, with respect to each of her beliefs, to give it up. She is therefore enmeshed in a deep and bottomless skepticism. One of her beliefs, however, is her belief in evolutionary naturalism itself; so then she also has a defeater for that belief. Evolutionary naturalism, therefore—the belief in the combination of naturalism and evolution—is self-refuting, self-destructive, shoots itself in the foot. Therefore you can't rationally accept it. For all this argument shows, it may be true; but it is irrational to hold it. So the argument isn't an argument for the falsehood of evolutionary naturalism; it is instead for the conclusion that one cannot rationally believe that proposition. Evolution, therefore, far from supporting naturalism, is incompatible with it, in the sense that you can't rationally believe them both.

To be fair, you can't rationally believe either.

Posted by Orrin Judd at August 11, 2008 4:55 PM