CHAPTER VII

INFERENCE AS A HABIT

In this chapter, we are concerned with inference as it can be observed when practised by some one else. Inference is supposed to be a mark of intelligence and to show the superiority of men to machines. At the same time, the treatment of inference in traditional logic is so stupid as to throw doubt on this claim, and syllogistic inference, which was taken as the type from Aristotle to Bacon (exclusive), is just the sort of thing that a calculating machine could do better than a professor. In syllogistic inference, you are supposed to know already that all men are mortal and that Socrates is a man; hence you deduce, what you never suspected before, that Socrates is mortal. This form of inference does actually occur, though very rarely. The only instance I have ever heard of was supplied by Dr. F. C. S. Schiller. He once produced a comic number of the philosophical periodical _Mind_, and sent copies to various philosophers, among others to a certain German, who was much puzzled by the advertisements. But at last he argued: “Everything in this book is a joke, therefore the advertisements are jokes”. I have never come across any other case of new knowledge obtained by means of a syllogism. It must be admitted that, for a method which dominated logic for two thousand years, this contribution to the world’s stock of information cannot be considered very weighty.

The inferences that we actually make in daily life differ from those of syllogistic logic in two respects, namely, that they are important and precarious, instead of being trivial and safe. The syllogism may be regarded as a monument to academic timidity: if an inference might be wrong, it was dangerous to draw it. So the mediæval monks, in their thinking as in their lives, sought safety at the expense of fertility.

With the Renaissance, a more adventurous spirit came into the world, but at first in philosophy, it only took the form of following Greeks other than Aristotle, and more especially Plato. It is only with Bacon and Galileo that the inductive method arrived at due recognition: with Bacon as a programme which was largely faulty, but with Galileo as something which actually led to brilliant results, namely, the foundation of modern mathematical physics. Unfortunately, when the pedants got hold of induction, they set to work to make it as tame and scholastic as deduction had been. They searched for a way of making it _always_ lead to true results, and in so doing robbed it of its adventurous character. Hume turned upon them with sceptical arguments, proving quite conclusively that if an induction is worth making it may be wrong. Thereupon Kant deluged the philosophic world with muddle and mystery, from which it is only now beginning to emerge. Kant has the reputation of being the greatest of modern philosophers, but to my mind he was a mere misfortune.

Induction, as it appears in the text-books, consists, roughly speaking, in the inference that, because A and B have been found often together and never apart, therefore they are probably always together, and either may be taken as a sign of the other. I do not wish, at this stage, to examine the logical justification of this form of argumentation; for the present, I am considering it as a _practice_, which we can observe in the habits of men and animals.

As a practice, induction is nothing but our old friend, the law of conditioned reflexes or of association. A child touches a knob that gives him an electric shock; after that, he avoids touching the knob. If he is old enough to speak he may state that the knob hurts when it is touched; he has made an induction based on a single instance. But the induction will exist as a bodily habit even if he is too young to speak, and it occurs equally among animals, provided they are not too low in the scale. The theories of induction in logic are what Freudians call a “rationalisation”; that is to say, they consist of reasons invented afterwards to prove that what we have been doing is sensible. It does not follow that they are bad reasons; in view of the fact that we and our ancestors have managed to exist since the origin of life, our behaviour and theirs must have been fairly sensible, even if we and they were unable to prove that it was. This, however, is not the point that concerns us at present. What concerns us at present is the fact that verbal induction is a late development of induction in behaviour, which is nothing more or less than the principle of “learned reactions”.

This principle, as the reader will remember, states that, if a certain event calls out a certain response, and if another event is experienced just before it, or at the same moment, in time that other event will tend to call out the response which, originally, only the first event would call out. This applies both to muscles and to glands; it is because it applies to glands that words are capable of causing emotions. Moreover, we cannot set limits to the length of the chain of associations that may be established. If you hold an infant’s limbs, you call out a rage reaction; this appears to be an “unlearned reaction”. If you, and no one else, repeatedly hold an infant’s limbs, the mere sight of you will call out a rage reaction after a time. When the infant learns to talk your name may have the same effect. If, later, he learns that you are an optician, he may come to hate all opticians; this may lead him to hate Spinoza because he made spectacles, and thence he may come to hate metaphysicians and Jews. For doing so he will no doubt have the most admirable reasons, which will seem to him to be his real ones; he will never suspect the process of conditioning by which he has in fact arrived at his enthusiasm for the Ku Klux Klan. This is an example of conditioning in the emotional sphere; but it is rather in the muscular sphere that we must seek the origin of the practice of induction.

Domestic animals which are habitually fed by a certain person will run towards that person as soon as they see him. We say that they expect food, and in fact their behaviour is very like what it would be if they saw food. But really we have only an example of “conditioning”: they have often seen first the farmer and then the food, so that in time they react to the farmer as they originally reacted to the food. Infants soon learn to react to the sight of the bottle, although at first they only react to the touch of it. When they can speak, the same law makes them say “dinner” when they hear the dinner-bell. It is quite unnecessary to suppose that they first think “that bell means dinner”, and then say “dinner”. The sight of dinner (by previous “learned reaction”) causes the word “dinner”: the bell frequently precedes the sight of dinner; therefore in time the bell produces the word “dinner”. It is only subsequent reflection, probably at a much later age, that makes the child say “I knew dinner was ready because I heard the bell”. Long before he can say this, he is acting as if he knew it. And there is no good reason for denying that he knows it, when he acts as if he