If my mental processes are determined wholly by the motions of atoms in my brain I have no reason to suppose that my beliefs are true ... and hence I have no reason for supposing my brain to be composed of atoms.Nor, if one's mental processes are in fact the result solely of an evolutionary process that selects for survival rather than truth, does one have epistemic justification for believing that naturalism is true since that belief was itself produced by cognitive faculties that evolved to promote survival rather than truth.
So how does the naturalist get around this apparent difficulty? Philosopher Jay Richards summarizes one common response:
If [the Darwinian natural selection] story is roughly correct, then there would seem to be a survival advantage in forming true beliefs. Surely our ancestors would have gotten on in the world much better if they came to believe that, say, a saber-tooth tiger, is a dangerous predator. And if they believed that they should run away from dangerous predators, all the better.On this account evolution would produce a propensity for holding true beliefs solely as a coincidental by-product of selecting for behaviors that are likely to increase the chances of surviving. There are several problems with this argument, however.
In contrast, those early humans who had false beliefs, who believed that saber-tooth tigers were really genies who would give three wishes if they were petted, would tend to get weeded out of the gene pool.
So wouldn’t the Darwinian process select for reliable rational faculties, and so give us faculties that would produce true beliefs?
One is that it assumes as a matter of faith that a non-rational process like natural selection can produce the rational faculties exhibited in human reason. What justifies the belief that rationality can arise from the non-rational?
But the bigger difficulty, as Richards writes, is that:
....there are millions of beliefs, few of which are true in the sense that they correspond with reality, but all compatible with the same behavior. Natural selection could conceivably select for survival-enhancing behavior. But it has no tool for selecting only the behaviors caused by true beliefs, and weeding out all the others.What Richards is getting at might be illustrated by a hypothetical example: Suppose two prehistoric tribes both encouraged the production of as many children as possible, but tribe A did so because they believed that the gods would reward those who produce many offspring with a wonderful afterlife.
Imagine also that tribe B had no belief in an afterlife but did believe that the more children one has the more likely some would survive to adulthood to care for the parents in their old age.
Natural selection would judge both of these tribes to be equally "fit" since the "goal" of evolution is to maximize reproductive success. Natural selection would only "see" the behavior, it would be blind to the beliefs that produced it. Thus, true beliefs would have no particular survival advantage over false beliefs, and cognitive faculties that produced true beliefs would not be any more likely to be selected for than faculties which produced false beliefs.
Richards concludes,
So if our reasoning faculties came about as most naturalists assume they have, then we have little reason to assume they are reliable in the sense of giving us true beliefs. And that applies to our belief that naturalism is true.Put differently, the naturalist cannot rationally justify his belief in naturalism. He can only maintain his belief that naturalism is true by an act of blind faith.
On the other hand, if our rational faculties have been instilled in us by a rational Creator then we have good reason to think that our reason is a reliable guide to truth. The theist, therefore, has much better grounds for trusting that the rational process will lead to truth than does the non-theist.
