C.S. Lewis’ Argument From Reason: Or, Why Naturalism Is Almost Certainly False

C.S. Lewis is famously known for his children’s fiction series, The Chronicles of Narnia. However, when it comes to defending the Christian worldview, Mere Christianity is the work he is often remembered for, including what has now become known as the trilemma, or the Lord, Liar, Lunatic argument. But Lewis’ apologetic prowess did not stop here. In a lesser read work, Miracles, he develops an argument against naturalism from the reality of human reason. This argument is quite powerful and proves to be yet another unsurmountable problem for the anti-God naturalistic worldview.

To begin, we need good definitions of our terms. Naturalism, in the words of Lewis, is the belief that “the ultimate Fact, the thing you can’t go behind, is a vast process in space and time which is going on of its own accord. Inside that total system every particular event (such as your sitting reading this book) happens because some other event has happened; in the long run, because the Total Event is happening…All the things and events are so completely interlocked that no one of them can claim the slightest independence from ‘the whole show.’” In short, the world is a series of natural causes and effects with the ultimate cause being the brute fact of an impersonal, mechanistic reality. There is no room for a God who stands outside and above nature, separate and distinct from it.

Now why is it that rationality poses such a problem for naturalism? First, if anything can be shown to exist that could not have its origin (in principle) in the mechanistic natural order, then naturalism suffers a fatal blow. Even if naturalism can’t be ruled out in principle, and let’s say reason just seems very improbable on naturalism, we have still undercut the presumption of naturalism. Second, if the conclusion (i.e. naturalism) invalidates or renders very uncertain the means (i.e. reason) used to reach that conclusion, then arguments for naturalism carry little weight, as they have sawed off the limb they were standing on.

Can Naturalism Account For Reason?

Events in nature operate on a cause and effect relationship. The water boils because the temperature reaches 212 degrees. The window broke because the ball went through. Reason is something of a different sort, in fact it is quite the opposite. Reason does not depend on the sort of natural cause and effect mentioned above. Reason or rationality, as Lewis points out, is not grounded in a cause-effect relationship. Rather, it rests on the logical relationship between things. “If our B does not follow logically from A, we think in vain.”

We all understand the need for reasoning to transcend the cause-effect relationship. In fact, we expect this and will discredit a man’s opinion if we believe it only has a natural cause. “He believes that because he is a man.” “She says that because she is rich and doesn’t want to let go of her money.” “You only hold that view because you are raised that way.” Natural causes do not give us grounds for believing a man’s opinion. Reason and logic are required, things that are different from the natural cause-effect relationship.

Natural cause and effect relationships, like water boiling at 212 degrees, is rooted in nature. The natural effect is rooted in a natural cause. But reasoning seems to transcend the natural world, possessing this weird quality of being “about” things, and operating on a logical relationship, not a natural one. Since the natural order does not seem to produce reason, in any meaning full sense, reason seems best explained by a source other than naturalism, a source possessing the quality of reason.

Can Naturalism Be Known If It Is True?

A further difficulty of the would-be defender of naturalism is his inability to have a sufficient ground for his reasoning processes. Naturalism, as seen above, doesn’t offer such a grounding. If my reasoning processes are only the result of natural causes, then what “reason” do I have to believe their conclusions. Lewis quotes 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.”

The question begs to be answered: “Why believe my reasoning if it is only the result of natural causes?” If you are a naturalist, or if naturalism happens to be true, it seems impossible to have any true knowledge of that fact. Lewis states it well: “All possible knowledge, then, depends on the validity of reasoning. If the feeling of certainty which we express by words like must be and therefore and since is a real perception of how things outside our own minds really ‘must’ be, well and good. But if this certainty is merely a feeling in our own minds and not a genuine insight into realities beyond them – if it merely represents the way our minds happen to work – then we can have no knowledge. Unless human reasoning is valid no science can be true.”

In this often overlooked argument, C.S. Lewis hammers a couple of nails in the coffin of a presumed naturalistic worldview. And if naturalism can’t account for reason, and even undercuts the ability to reason, then we have opened the door to a supernatural worldview, a world where nature is not all that exists, a world where reason, miracles, and the supernatural are possible.