The argument from reason is a name applied to an argument, or a group of arguments, which attempt to make a case against a naturalistic philosophy by pointing out that such a philosophy undercuts the claim to hold rational beliefs. The argument is best-known in the writings of C. S. Lewis, but is considerably older. Some have actually found this line of argumentation as far back as Plato, and a version of it is found in Kant.
What these arguments invariably target are doctrines known as naturalism, materialism, or physicalism. All of these concepts are notoriously difficult to define. What seems to be common to all of them is the idea that at the basis of reality are elements which are entirely non-mental in nature. We can begin thinking about this by contrasting two different types of explanation. One type of explanation is what might be provided by how we might explain the movement of rocks down a mountain in an avalanche. If I am standing down at the bottom of the mountain, we can expect the rocks to move where they do without regard to whether my head is in their path or not. They will not deliberately move to hit my head, neither will they move to avoid it. They will do what the laws of physics require that they do, and if my head is in the wrong place at the wrong time, it will be hit, and otherwise it will not be hit. The process is an inherently blind one.
Consider, by contrast, how we might explain what happens when I decide to vote for a certain candidate for President. I weigh the options, and choose the candidate who is most likely to do what I want to see done in the country for the next four years. The action of voting for Obama or Romney is one filled with intention and purpose. I know what the choice is about, I have a goal in mind when voting, and I perform the act of voting with the intent to achieve a certain result.
If we look at the world from a naturalistic perspective, we are always looking to find non-mental explanation even behind the mental explanations that we offer. Take, for example, Einstein developing his theory of relativity. If a naturalistic view of the world is correct, then we can, and must explain the development of Einstein’s theory in mental terms, in terms of certain mathematical relationships obtaining, and so forth. But, Einstein’s brain is, according to the naturalist, entirely the result of a purely non-intention process of random variation and natural selection. The appearance of intention and design is explained by an underlying blind process that not only produced Einstein’s brain, but also, the processes in his brain are the result of particles in his brain operating as blindly as the rocks falling down the avalanche and either hitting or not hitting my head at the bottom of the mountain.
Contrast this with a theistic view. On such a view, there may be particles the follow the laws of physics, but those laws are in place because they were built into creation by God. Presumably, if God had wanted there to be other laws of physics, he could have made a world with laws of physics very different than the ones that we see. So, on the theistic view we see the opposite of naturalism. Even what seems on one level to be completely explained in terms of the non-mental has a mental explanation.
The argument from reason tries to show that if the world were as the naturalist, or materialist, or physicalist, says that it is, then no one can be rational in believing that it is so. Rational beliefs must, according to the argument, must have rational causes, but naturalism holds that, in the final analysis, all causes are non-rational causes. But if this is so, then human beings really don’t reason, and if they don’t reason, they don’t do science either. So, the very naturalistic world-view which is supposed to be based on science, is actually the very view that render science impossible.
In the original 1947 edition of his book Miracles: A Preliminary Study, Lewis presented a version of the argument from reason which can be formalized as follows.
1) If naturalism is true, then all thoughts including the thought “naturalism is true,” can be fully explained as the result of irrational causes.
2) If all thoughts that are the result of irrational causes, then all thoughts are invalid, and science is impossible.
3) If all thoughts are invalid, and science is impossible, then no one is justified in believing that naturalism is true.
4) Therefore naturalism should be rejected.
In 1948, the Roman Catholic philosopher Elizabeth Anscombe argued that against Lewis’s argument in a paper at the Oxford Socratic Club. She argued, first that one has to distinguish between irrational causes on the one hand, and non-rational causes on the other. Irrational causes for a belief would be such things as wishful thinking or mental illness, or unreasonable fears. Irrational causes always interfere with the possibility of believing rationally. Non-rational causes would by physical events which, while not rational, don’t necessarily make rationality impossible. While naturalists hold that all thoughts are the result of nonrational causes, they need not hold that they are the result of irrational cases.
Second, she argued that when we say that something or other makes a thought invalid, we are presuming a contrast between valid and invalid thoughts. Hence, the very existence of the distinction entails that some thoughts are valid and others are not, and so it cannot be the conclusion of an argument that no thoughts are valid.
Third, she argued that there is an ambiguity in the terms “why,” “because” and “explanation” conceal the possibilities that a naturalistic explanation and a rational explanation might not actually turn out to be compatible. Thus, when we are asking “why” in the context of identifying a cause for a certain event, we are asking a radically different question from when we are asking “why” when we are asking why someone believes something. Thus, we could simultaneously give “because such and such brain event caused it,” and “because there is good evidence to think it true” as explanations without contradicting ourselves.
Now, in response to these arguments by Anscombe, some responses can be made on Lewis’s behalf. First, with respect to Anscombe’s first argument, Lewis had already drawn the distinction between nonrational and irrational causes, when he distinguished between two types of irrational causes. He wrote:
“Now the emotion, thus considered by itself, cannot be in agreement or disagreement with Reason. It is irrational not as a paralogism is irrational, but as a physical event is irrational: it does not rise even to the dignity of error.”
With both nonrational causes, in Anscombe’s sense, and irrational causes, reason is absent from the causal process. Yet, in paradigmatic cases reasoning that a naturalist cannot deny ever occur, such as the reasoning process that led Darwin to explain the variation in beak sizes on the Galapagos islands in terms of natural selection, reasoning is definitely present. Naturalistic thinkers frequently insist that people require evidence for their beliefs as opposed to believing on blind faith, but this implies that reasons can and do play a critical role in the production of many beliefs. If this were not so, there would be no science.
Second, while it might be unsound to argue that there no thoughts are valid, the conclusion of Lewis’s argument is the conditional statement, “If naturalism is true, then no thoughts are valid.” So, even though Anscombe’s paradigm case argument might show that there must be a contrast between rational and irrational thoughts, Lewis can affirm that there is indeed such a contrast, but existence of such a contrast can exist only if naturalism is false.
Third, although causal relationships are different from evidential relationships, when we think about being persuaded to believe something, we are inclined to suppose that somehow the fact that an evidential relationship obtains is causally relevant to the actual occurrence of belief as a psychological event. Anscombe actually says “It appears to me that if a man has reasons, and they are good reasons, and they genuinely are his reasons, for thinking something, then his thought is rational, whatever causal statements may be said about him.” (Anscombe, 1981, p.299.) But it seems to me that part of what it is for something to be someone’s reasons for believing something has to do with the role those reasons play not only in producing, but also sustaining that belief. If someone gives a reason for believing something, but it turns out that the presence or absence of that reason would have absolutely nothing to do with whether or not a person continued to believe what he does, then it is questionable whether these reasons are operative at all.
If you were to meet a person, call him Steve, who could argue with great cogency for every position he held, you might be inclined to consider him a very rational person. But if you were to discover that he rolled dice to fix permanently all his beliefs, you might on that account be inclined to withdraw from him the honorific title “rational.” We sometimes consider persons who continue to hold the positions they hold regardless of the evidence against such positions impervious to reason. But if naturalism true, it might be argued that everyone is impervious to reason, because, in the final analysis, because the existence of reasons is irrelevant to how beliefs are produced and sustained. In the last analysis, all beliefs are caused, not by mental, but rather by physical, and therefore nonmental causes.