Miracles. C. S. Lewis

We should be in a pretty pickle if we could never think ‘This is glass’ without drawing all the inferences which could be drawn. It is impossible to draw them all; quite often we draw none. We must therefore amend our suggested law. One thought can cause another not by being, but by being seen to be, a ground for it.

      If you distrust the sensory metaphor in seen, you may substitute apprehended or grasped or simply known. It makes little difference for all these words recall us to what thinking really is. Acts of thinking are no doubt events; but they are a very special sort of events. They are ‘about’ something other than themselves and can be true or false. Events in general are not ‘about’ anything and cannot be true or false. (To say ‘these events, or facts are false’ means of course that someone’s account of them is false). Hence acts of inference can, and must, be considered in two different lights. On the one hand they are subjective events, items in somebody’s psychological history. On the other hand, they are insights into, or knowings of, something other than themselves. What from the first point of view is the psychological transition from thought A to thought B, at some particular moment in some particular mind, is, from the thinker’s point of view a perception of an implication (if A, then B). When we are adopting the psychological point of view we may use the past tense. ‘B followed A in my thoughts.’ But when we assert the implication we always use the present—‘B follows from A’. If it ever ‘follows from’ in the logical sense, it does so always. And we cannot possibly reject the second point of view as a subjective illusion without discrediting all human knowledge. For we can know nothing, beyond our own sensations at the moment unless the act of inference is the real insight that it claims to be.

      But it can be this only on certain terms. An act of knowing must be determined, in a sense, solely by what is known; we must know it to be thus solely because it is thus. That is what knowing means. You may call this a Cause and Effect because, and call ‘being known’ a mode of causation if you like. But it is a unique mode. The act of knowing has no doubt various conditions, without which it could not occur: attention, and the states of will and health which this presupposes. But its positive character must be determined by the truth it knows. If it were totally explicable from other sources it would cease to be knowledge, just as (to use the sensory parallel) the ringing in my ears ceases to be what we mean by ‘hearing’ if it can be fully explained from causes other than a noise in the outer world—such as, say, the tinnitus produced by a bad cold. If what seems an act of knowledge is partially explicable from other sources, then the knowing (properly so called) in it is just what they leave over, just what demands, for its explanation, the thing known, as real hearing is what is left after you have discounted the tinnitus. Any thing which professes to explain our reasoning fully without introducing an act of knowing thus solely determined by what is known, is really a theory that there is no reasoning.

      But this, as it seems to me, is what Naturalism is bound to do. It offers what professes to be a full account of our mental behaviour; but this account, on inspection, leaves no room for the acts of knowing or insight on which the whole value of our thinking, as a means to truth, depends.

      It is agreed on all hands that reason, and even sentience, and life itself are late comers in Nature. If there is nothing but Nature, therefore, reason must have come into existence by a historical process. And of course, for the Naturalist, this process was not designed to produce a mental behaviour that can find truth. There was no Designer; and indeed, until there were thinkers, there was no truth or falsehood. The type of mental behaviour we now call rational thinking or inference must therefore have been ‘evolved’ by natural selection, by the gradual weeding out of types less fitted to survive.

      Once, then, our thoughts were not rational. That is, all our thoughts once were, as many of our thoughts still are, merely subjective events, not apprehensions of objective truth. Those which had a cause external to ourselves at all were (like our pains) responses to stimuli. Now natural selection could operate only by eliminating responses that were biologically hurtful and multiplying those which tended to survival. But it is not conceivable that any improvement of responses could ever turn them into acts of insight, or even remotely tend to do so. The relation between response and stimulus is utterly different from that between knowledge and the truth known. Our physical vision is a far more useful response to light than that of the cruder organisms which have only a photo-sensitive spot. But neither this improvement nor any possible improvements we can suppose could bring it an inch nearer to being a knowledge of light. It is admittedly something without which we could not have had that knowledge. But the knowledge is achieved by experiments and inferences from them, not by refinement of the response. It is not men with specially good eyes who know about light, but men who have studied the relevant sciences. In the same way our psychological responses to our environment—our curiosities, aversions, delights, expectations—could be indefinitely improved (from the biological point of view) without becoming anything more than responses. Such perfection of the non-rational responses, far from amounting to their conversion into valid inferences, might be conceived as a different method of achieving survival—an alternative to reason. A conditioning which secured that we never felt delight except in the useful nor aversion save from the dangerous, and that the degrees of both were exquisitely proportional to the degree of real utility or danger in the object, might serve us as well as reason or in some circumstances better.

      Besides natural selection there is, however, experience—experience originally individual but handed on by tradition and instruction. It might be held that this, in the course of millennia, could conjure the mental behaviour we call reason—in other words, the practice of inference—out of a mental behaviour which was originally not rational. Repeated experiences of finding fire (or the remains of fire) where he had seen smoke would condition a man to expect fire whenever he saw smoke. This expectation, expressed in the form ‘If smoke, then fire’ becomes what we call inference. Have all our inferences originated in that way?

      But if they did they are all invalid inferences. Such a process will no doubt produce expectation. It will train men to expect fire when they see smoke in just the same way as it trained them to expect that all swans would be white (until they saw a black one) or that water would always boil at 212° (until someone tried a picnic on a mountain). Such expectations are not inferences and need not be true. The assumption that things which have been conjoined in the past will always be conjoined in the future is the guiding principle not of rational but of animal behaviour. Reason comes in precisely when you make the inference ‘Since always conjoined, therefore probably connected’ and go on to attempt the discovery of the connection. When you have discovered what smoke is you may then be able to replace the mere expectation of fire by a genuine inference. Till this is done reason recognises the expectation as a mere expectation. Where this does not need to be done—that is, where the inference depends on an axiom—we do not appeal to past experience at all. My belief that things which are equal to the same thing are equal to one another is not at all based on the fact that I have never caught them behaving otherwise. I see that it ‘must’ be so. That some people nowadays call axioms tautologies seems to me irrelevant. It is by means of such ‘tautologies’ that we advance from knowing less to knowing more. And to call them tautologies is another way of saying that they are completely and certainly known. To see fully that A implies B does (once you have seen it) involve the admission that the assertion of A and the assertion of B are at bottom in the same assertion. The degree to which any true proportion is a tautology depends on the degree of your insight into it. 9 × 7 = 63 is a tautology to the perfect arithmetician, but not to the child learning its tables nor to the primitive calculator who reached it, perhaps, by adding seven nines together. If Nature is a totally interlocked system, then every true statement about her (e.g. there was a hot summer in 1959) would be a tautology to an intelligence that could grasp that system in its entirety. ‘God is love’ may be a tautology to the seraphim; not to men.

      ‘But’, it will be said, ‘it is incontestable that we do in fact reach truths by inferences’. Certainly. The Naturalist and I both admit this. We could not discuss anything unless we did. The difference I am submitting is that he gives, and I do not, a history of the evolution of reason which is inconsistent with the claims that he and I both have to make for inference as we actually practise it. For his history is, and from the nature of the case can only be, an account, in Cause and Effect terms, of how people came to think the way they