A few weeks ago I attended a workshop that was entitled “Becoming Human: A Brief Evolutionary History of Man”. At the end of the workshop we were assigned a paper of which we had a week to complete. The paper had to be about evolution. So I asked my professor “I am a philosophy major, so can I really write ANYTHING about evolution?” When he replied in the affirmative I was excited and it got me thinking about the very problem we are to discuss in this post.

This topic has been put forth by theist and atheist philosophers alike, the idea is that if evolution and naturalism are both true then “the probability of having reliable cognitive faculties is low.”1 Alvin Plantinga, Richard Taylor, Stephen Clark, J.P. Moreland, etc. all have somewhat similar arguments, and while I could be persuaded otherwise, I don’t believe any of them are correct. Is it fair to speak of probabilities of that which you have no empirical evidence for? I would be weary of jumping on that boat too quickly since the justification of that belief doesn’t seem to strike me at face value. So I considered a more mathematical or formal approach with logic.I performed a proof by reductio ad absurdum (if anyone wants to see the formal proof in symbols let me know in the comments) and I arrived at contradictions.

We are starting by assuming evolution and naturalism are both true. From here we have only two options 1.) We either evolved the illusion of rationality or 2.) We did in fact evolve rational brains.

1.) Asserting the truth of this premise means all of logic is only an illusion. This also means that mathematical truths, logical truths, and metaphysical truths are accidental by-products of a brain that was trying to evolve with traits best fit for survival but not brains best fit for making necessary truth claims. This defeats both naturalism and evolution since they are also by-products of an irrational mind.

2.) This premise means we did, by accident, evolve an objective rationality that lets us know necessary truths, including mathematical, logical, and metaphysical truths. This means that mathematical truth claims are true. Since mathematical claims are true this means that numbers exist (this is a because you can’t make truth claims about things that do not exist 2). If numbers exist then at least one set of abstract objects exists. If at least one set of abstract objects exists then naturalism is not true.

The conclusion is, in my opinion,fairly modest. Either evolution is not the case or naturalism is not the case (or both). But neither of them, it seems, can be true at the same time. To assert the truth of both of them is to arrive at contradictions.