“If minds are wholly dependent on brains and brains on biochemistry, and biochemistry (in the long run) on the meaningless flux of the atoms, I cannot understand how the thought of those minds should have any more significance than the sound of the wind in the trees.” – C. S. Lewis1
The Argument
Atheism is logically consistent with a number of metaphysical viewpoints, but I will focus on the kind of atheism most popular in western society: metaphysical naturalism. For the modern atheist, the evolutionary story is the only option when it comes to a theory of human origins, so it is a critical doctrine for any atheist in western culture. However, I want to argue that belief in the conjunction of evolution and naturalism is self-defeating. That is, if evolution and naturalism are both true, then it is irrational to believe that they are true. Alvin Plantinga has made popular an argument he names the Evolutionary Argument against Naturalism. Of course, the argument is not entirely original to Alvin Plantinga. C. S. Lewis wrote about this sort of thing as well, as noted by the quote above. However, I will follow Plantinga’s way of developing the argument as he does in his book Warrant and Proper Function while trying to keep it simple and put things into my own words. The argument is simple and intuitive, as Lewis’s quote shows. Fleshing it out in a bit of detail will be the task of this article.
By “naturalism” I mean the metaphysical view that nature is all that exists. Nature is constituted by physical particles in motion acting in accordance with the laws of physics. You can also refer to this as materialism or physicalism. Jaegwon Kim describes this view in his book on philosophy of mind. He says, “The most fundamental tenet of physicalism concerns the ontology of the world. It claims that the content of the world is wholly exhausted by matter. Material things are all the things that there are; there is nothing inside the spacetime world that isn’t material, and of course there is nothing outside it either. The spacetime world is the whole world, and material things, bits of matter and complex structures made up of bits of matter, are its only inhabitants. This doctrine is sometimes called ‘ontological physicalism.’”2 The relevant aspect of this view for our discussion here is that on naturalism/materialism/physicalism, God does not exist. This means that human beings were not created by an intentional, rational Mind but are rather the end products of chemical and biological evolution. By “evolution” I mean the dominant theory of how life’s complexity came about beginning with simple life forms and being developed through genetic mutation and natural selection (among other things). You, as a human being, are not a special creation of a rational Mind. You are just an accidental byproduct of random physical processes. Now, it is important to remember that the target of this article is the conjunction of naturalism and evolution. If theism is true, then it is possible that God guided evolution, thus ensuring our minds would be reliable, so evolution is not problematic on its own. It becomes a problem when paired with naturalism. If naturalism is true, I am not sure what theory of life development could be viable other than evolution.
Now, if naturalism and evolution are true, then our cognitive faculties have not come about for the purpose of attaining true beliefs. Evolution has no such aim. Rather what accounts for an organism’s survival is its behavior. “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…feeding, fleeing, fighting and reproducing. The principle [sic] 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 [Churchland’s emphasis]. Truth, whatever that is, definitely takes the hindmost.”3Truth has no part in evolution, or it at least “takes the hindmost”. On evolution, it is not necessary that organisms have true beliefs at all. All that matters is that they move in such a way that helps them survive. Plantinga says, “naturalistic evolution—that is, the conjunction of metaphysical naturalism with the view that we and our cognitive faculties have arisen by way of the mechanisms and processes proposed by contemporary evolutionary theory—gives us reason to doubt two things: (a) that a purpose of our cognitive systems is that of serving us with true beliefs, and (b) that they do, in fact, furnish us with mostly true beliefs.”4This presents a problem for the believer in both evolution and naturalism. Because your cognitive faculties were formed for the enhancement of survival, not the production of true beliefs, the probability that your cognitive faculties are reliable is very low. You have no reason to trust that they actually produce true beliefs as opposed to false-but-survival-enhancing beliefs. And even saying “formed for the…” is not exactly correct because that presupposes some sort of goal or intention, but on naturalism and evolution, there is no goal at all. Everything about an organism is just an accident that just happened to enhance survival probability. Now, if our cognitive faculties are not reliable, then every belief produced by them is irrational. Thus, the belief that naturalism and evolution are both true is irrational. Herein lies the self-defeating nature of naturalism and evolution. If true, the belief defeats itself. There is no rational way to accept it.
The Objection
The objection to this argument is simple: organisms must have mostly true beliefs in order to survive. Therefore, we may indeed trust our cognitive faculties. In other words, “belief is connected with action in such a way that extensive false belief would lead to maladaptive behavior”5, so the fact that we as organisms are still around shows that our cognitive faculties are reliable. However, there is in fact no reason to believe that belief and behavior are so connected, and even if they are, we still could not trust that the beliefs such cognitive faculties produce are mostly true. Plantinga notes five possible relations between belief and behavior on naturalistic evolution and shows that on all five, the probability that our cognitive faculties are reliable is low.
Beliefs are mere epiphenomena.
On this, beliefs have literally nothing to do with behavior at all. So, the probability of our cognitive faculties being reliable has to be incredibly low. It seems to me that this is the most probable situation on naturalistic evolution.
Beliefs are effects but not causes of behavior.
On this, beliefs don’t factor in as causes to behavior, so beliefs are irrelevant in producing advantageous action.
Beliefs do indeed have causal power over behavior but not in virtue of their content.
On this, beliefs do affect behavior, but the behavior is not connected to the content or meaning of the beliefs, so the beliefs could have content that is wildly false yet still influence the organism.
Beliefs have causal power over behavior in virtue of their content, but the behavior is maladaptive.
On this, beliefs and their content affect behavior, but the behavior is maladaptive, thus leading to these organisms dying and becoming extinct.
Beliefs have causal power over behavior and are indeed advantageous for survival.
Finally, on this, beliefs are connected to behavior in a beneficial way. Surely, as the objection states above, on this view, our cognitive faculties are reliable. But maybe they are not. Plantinga says, “…beliefs don’t causally produce behavior by themselves; it is beliefs, desires, and other things that do so together. Suppose we oversimplify a bit and say that my behavior is a causal product just of my beliefs and desires. Then the problem is that clearly there will be any number of different patterns of belief and desire that would issue in the same action; and among those there will be many in which the beliefs are wildly false.”6 Even if our beliefs were causally relevant to our survival, the beliefs (combined with desires and presumably more) could still be wildly false and yet lead to survival. Thus, the mere fact that we are still around does not show that our cognitive faculties are reliable.
One more important thing needs to be mentioned. Even if mostly true beliefs were required for survival, these would surely be very basic perceptual beliefs such as, “There is a dangerous predator near me.” Thus, more abstract beliefs such as those derived from theoretical physics, moral philosophy, and biology that have nothing to do with survival would be doubtful. The cognitive faculties held by such creatures formed in naturalistic evolution would be very unlikely to have the cognitive power to achieve what we humans have achieved in our intellectual history.
Theism
Naturalism is not the only game in town, however. And if you, with everyone else, are convinced that we humans do have reliable minds, then you may want to seek another worldview: theism. I will speak specifically of Christian theism. On Christian theism, God has created us to be like Him in certain ways, one of which is the ability to rationally reflect, understand, and know truth. We can be sure that our minds are reliable because He is good and able to create us with the minds to do this. Reliable cognitive faculties are at home in a theistic world, but they are very unlikely in a naturalistic world.
Summary
If naturalism and evolution are true, then our minds are the accidental results of chemical and biological evolution where all that matters is survival-enhancing behavior—not true beliefs. If this is the case, then the chances of our cognitive faculties being reliable in giving us mostly true beliefs is very low. And if this is the case, then it follows that all of our beliefs are irrational, not having been produced by reliable cognitive faculties. If all of our beliefs are irrational and naturalistic evolution is one of our beliefs, then that belief is irrational. Thus, naturalistic evolution defeats itself. It is not rational to believe. It shoots itself in the foot, so to speak. However, on theism, we have good reason to believe that our minds are reliable in giving us true beliefs. An all-powerful, good, and rational Creator has created us with the intention and ability to give us reliable minds that we may seek truth and attain it rationally.