C.S. Lewis wanted to explain nature on the basis of his supernatural god; as a consequence, naturalistic explanations for nature represented a major threat â€" just as it does for contemporary apologists. Lewis argued against naturalism in a variety of contexts. It plays an important role not just in his discussions about morality, but also in his arguments about the nature of reason.
In his book Miracles, Lewis argues against naturalism by saying “If Naturalism is true, every finite thing or event must be (in principle) explicable in terms of the Total System.†This isn’t necessarily true. Lewis was aware of advances in physics which revealed that events on the quantum level were probabilistic rather than deterministic, but he regarded this as a reason to think that there exists something more than “Nature†rather than as a reason to think that maybe nature isn’t quite what he (like others) assumed it to be. He rejected the findings of science because they conflicted with his assumptions.
Lewis appears not to have understood that some events and systems are, even in principle, not explainable despite being entirely natural. No one disputes that the weather is completely natural, but while weather events can be predicted to varying degrees of accuracy, it’s not possible even in principle to explain every facet of them because they are too complex, chaotic, and probabilistic.
Part of the problem is that Lewis adopts a very limited, narrow understanding of naturalism. For Lewis, naturalism is the same as determinism. Thus, what we encounter is a tactic which Lewis uses continually: the construction of a false dilemma fallacy in which he presents the “wrong†option in an unfavorable and incorrectly defined way against the “right†option which, he hopes, will seem more reasonable against his straw man. The idea of a third option, like rejecting both extreme determinism and supernaturalism, is never entertained.
From this inauspicious beginning, things only go down hill. Lewis argues that nature cannot explain the existence of Reason:
“A strict materialism refutes itself for the reason given long ago by Professor Haldane: ‘If my mental processes are determined wholly by the motions of atoms in my brain, I have no reason to suppose that my beliefs are true...and hence I have no reason for supposing my brain to be composed of atoms.’ (Possible Worlds, p. 209)†In other words, because atoms are not themselves rational, then they alone cannot be responsible for rationality because such an irrational foundation cannot be a reliable basis for rational thinking. This absurd reasoning would preclude atoms being responsible for anything at all â€" atoms aren’t visible to the naked eye, so how could they produce anything visible? It’s known as the fallacy of composition and is just one more example of Lewis constructing fallacious arguments in the apparent hope that no one would notice.
On February 2, 1948, G.E.M. Anscombe read a paper to the Oxford Socratic Club criticizing this section of C.S Lewis’ book, identifying several serious weaknesses. According to George Sayer, a friend of Lewis, he recognized that his position was soundly refuted:
“He told me that he had been proved wrong, and that his argument for the existence of God had been demolished. ...The debate had been a humiliating experience, but perhaps it was ultimately good for him. In the past, he had been too proud of his logical ability. Now he was humbled ....’I can never write another book of that sort’ he said to me of Miracles. And he never did. He also never wrote another theological book. Reflections on the Psalms is really devotional and literary; Letters to Malcolm is also a devotional book, a series of reflections on prayer, without contentious arguments.â€
Lewis never publicly acknowledged his defeat, but he did respond. The relevant chapter was renamed from “Naturalism is Self-Refuting†to “The Cardinal Difficulty of Naturalism.†Some statements were revised and he removed the egregious claim that “We may state it as a rule that no thought is valid if it can be fully explained as the result of irrational causes.â€
These revisions are not enough to salvage his argument because its flaws are fundamental. Lewis relied, for example, on a bizarre epistemology, according to which knowledge can only be attained indirectly by inferring from sensory perception to the objects supposedly lying behind them. Because of this, he felt that reliable knowledge depends upon logical reasoning â€" that we cannot come to have true, justified beliefs about the world without it.
This is a peculiar and extreme form of rationalism, but it’s not an epistemology which is compatible with modern science and thinking. It doesn’t enjoy wide currency today, even among Christians who ostensibly accept Lewis’ apologetics. If they do not accept the epistemological assumptions he uses, though, they cannot also accept his theological conclusions which they find so appealing.
