Alvin Plantinga, Part II

This is part II of my discussion of Plantinga’s evolutionary argument against naturalism. Part I was here.

There are four possible hypothesis regarding the origins of our ability to reason. 1) Our brains arose by natural selection or other natural processes and has produced reliable mechanisms of finding truth. 2) Our brains arose by natural selection or other natural processes and are not reliable. 3) Our brains arose by some mechanism other than natural selection, perhaps supernatural, and has produced reliable mechanisms of finding truth. 4) Our brains arose by some mechanism other than natural selection, perhaps supernatural, and are not reliable.

I need to clarify two things. First, this is artificially restricting the possibilities. For example, reason might have arisen by evolution, but not by natural selection (it could be a Spandrel, for example). Perhaps we were designed by Aliens. Since Plantinga is basically arguing against naturalism, more than against evolution, I tried to group all natural explanations in one, and supernatural in another.

Second, in 1) and 3), I only claim that we have at least some means of determining true beliefs. I need not claim that all of our senses or brain function produces true belief. We could easily argue whether or not beliefs that aid in survival are likely to be true beliefs or not. Much of the discussion of Plantinga’s argument revolves around these. Some of it has the form of just so arguments—it is easy to come up with a story to show how survival could or could not correlate with truth. For this, I will make the reasonable assumption that sometimes there will be such a correlation, and sometimes there will not be. If that is true, then our brains and eyes should sometimes give us accurate information about the world, and sometimes deceive us. Regardless of whether we are the product of natural selection, this is what we observe—we are prone to logical fallacies, visual illusions, etc., but also seem capable of higher reasoning.

I understand Plantinga as arguing that if we arose by evolution, we have no way to distinguish between 1) and 2). We can’t tell if our beliefs are reliable or not. If he is making the much stronger claim that 1) could not be true, he requires a much higher standard of evidence. He must show not just that evolution can produce false beliefs, but that it could never produce true beliefs. He must show that survival and true beliefs never coincide. I do not believe such a claim could be supported, as I discussed above. I fully agree that sometime evolution will produce false beliefs, but contend in 1) that sometimes it produces true beliefs.

If 2) were true, then our brains should be well designed for survival, but should not be able to do things that require true understanding of the world but do not aid in survival. That is a testable prediction. If 2) were true, we should not be able to make airplanes or solve the Rubic’s cube. The success of science, and the many other ways we use our brains for things other than survival, is evidence that our brains are reliable, at least sometimes. Therefore, we can rule out 2) and 4). We are left with a reliable brain that either arose by natural processes or by supernatural processes.

Since we have determined that our brains are reliable, we can no longer dismiss all of the evidence for evolution. Plantinga tried to dismiss the overwhelming case for evolution by saying we can’t trust our brains and thus can’t trust the evidence for evolution. Now that we have shown our brains are reliable, the way to distinguish between 1) and 3) is simply to look at the evidence. We have escaped Plantinga’s circular and unfalsifiable argument.

Plantinga would claim our brains are reliable, but arose through supernatural means. He then has a few conundrums of his own. He believes we can trust our brains, and therefore we can't dismiss the evidence for evolution. It's only once you dismiss evolution that he has a way to dismiss the evidence. Also, evolution can easily explain both why our brains are sometimes reliable, and why they so often fails us. If we arose by supernatural means, why did God give us such imperfect brains?

Unlike most anti-evolution arguments, this is not a scientific argument. It is a philosophical argument, an argument from epistimology. I respect much of philosophy. It can help us to know the world. However, sometimes it becomes nothing but word games and sophistry. I think that is what we have here.