(1) No belief is rationally inferred if it can be fully explained in terms of non-rational causes.
(2) If naturalism is true, then all beliefs can be fully explained in terms of non-rational causes.
(3) Therefore, if naturalism is true, then no belief is rationally inferred.
(4) If any thesis entails the conclusion that no belief is rationally inferred, then it should be accepted and its denial accepted.
Conclusion: naturalism should be rejected and its denial accepted.
The problem with this argument is (1), upon closer examination this is an unfounded assumption. Of course the non-rational causes themselves are not rational, but this does not mean their interactions cannot be. In fact, there are numerous examples in nature of the interactions of a system having new properties which the individual components lack. Such emergent properties are well demonstrated, for instance, in the complex properties of all biological organisms (such as the trait I discussed in my article about a novel definition of life). Given that such examples are so abundant, it seems very plausible that rationality could be an emergent property from the interactions of non-rational causes. To be clear, this does not prove that non-rational causes interact to produce rationality. However, it does provide compelling reason to suspect that they may. A claim as bold as (1) would require justification for the argument to be sound.
(5) A being requires a rational process to assess the truth or falsehood of a claim (hereinafter, to be convinced by argument).
(6) Therefore, if humans are able to be convinced by argument, their reasoning processes must have a rational source.
(7) Therefore, considering element two above, if humans are able to be convinced by argument, their reasoning processes must have a non-physical (as well as rational) source.
(8) Rationality cannot arise out of non-rationality. That is, no arrangement of non-rational materials creates a rational thing.
(9) No being that begins to exist can be rational except through reliance, ultimately, on a rational being that did not begin to exist. That is, rationality does not arise spontaneously from out of nothing but only from another rationality.
(10) All humans began to exist at some point in time.
(11) Therefore, if humans are able to be convinced by argument, there must be a necessary and rational being on which their rationality ultimately relies.
Conclusion: this being we call God.
Notice that (7), (8), and (9) are extremely related to (2), which I have already discussed. In fact, my refutation of (2) is equally applicable to these points. The assumption that rationality must be nonphysical and cannot be formed through the interactions of non-rational elements is unsubstantiated. As before, the idea that rationality is an emergent property from the interaction of non-rational elements continues to be a viable possibility.
A serious difficulty results from (5), it deals with whether or not humans can accurately tell if a claim is true or false. That is, if in general human reasoning is valid or not. Lewis assumes that humans are capable of valid reasoning and argues that the existence of God is required for this. Without God, he contends valid reasoning would not be possible because of (7). The problem here is that making a general claim one way or the other about whether or not humans are capable of valid reasoning is an absurd concept. The philosopher Elizabeth Anscombe has argued that the notion of validity or invalidity can be known only through experiencing both. For instance, suppose we assume that human reasoning is always invalid. It would be necessary for us to experience at least one instance of valid reasoning to have the notion of invalid reasoning, but this obviously contradicts the original claim that human reasoning is always invalid. Thus Lewis’s general claims about the validity of human reasoning inevitably introduce contradiction into his argument.
Lewis’s assumption that humans are able to assess the truth or falsehood of a claim is worth further attention. This is a very conventional idea, scientists and many philosophers (except those whose research interests include this very issue!) do not regularly question if this is so. It would certainly be bad news for human knowledge if our reasoning was invalid. The legitimacy of science, philosophy, and mathematics hinges on the assumption that human reasoning is valid. The importance to us of this being true does not mean it must be, however. That is merely wishful thinking. That being said, the reproducibility of science and the accuracy of many of its predictions suggest that even if our reasoning is invalid, it seems to work pretty well. The usefulness of mathematics is also a testament to this. Of course working well and actually being true are different things. From an evolutionary prospective it seems that working well would be the important criterion for our cognitive skills, rather than how accurate or truthful they really are. The important question then becomes if invalid reasoning could function as well as valid reasoning in our universe. If not, then we certainly must have valid reasoning. This is not a question which I claim to have the answer to though. Whether or not our reasoning is valid is uncertain. Challenging this assumption is fundamentally difficult, however. Questioning the validity of human reasoning is synonymous with questioning the argument that it ought to be questioned itself. Thus it is impossible to logically argue that human reasoning is invalid. Indeed this is the basis of Lewis’s argument from reason. Although the assumption may be wrong, his argument cannot be criticized for this reason (except in self-contradicting ways, that is). Lewis makes an interesting argument, but it ultimately fails to disprove naturalism or show that God exists.
Without the mysticism of the supernatural, it is often thought that naturalism must be an extremely dismal view. It describes an indifferent universe which is both amoral and without purpose. Seeing the universe in this way does not condemn us to have these traits ourselves though. In fact, their acceptance provides all the more reason to live a life that is virtuous and meaningful. In his essay “The Free Man’s Worship” Bertrand Russell wrote,
That man is the product of causes which had no prevision of the end they were achieving; that his origin, his growth, his hopes and fears, his loves and his beliefs, are but the outcome of accidental collocations of atoms; that no fire, no heroism, no intensity of thought and feeling, can preserve an individual life beyond the grave; that all the labours of the ages, all the devotion, all the inspiration, all the noonday brightness of human genius, are destined to extinction in the vast heat death of the solar system, and that the whole temple of Man’s achievement must inevitably be buried beneath the debris of a universe in ruins – all these things, if not quite beyond dispute, are yet so nearly certain that no philosophy which rejects them can hope to stand. Only within the scaffolding of these truths, only on the firm foundation of unyielding despair, can the soul’s habitation henceforth be safely built.