(i) As regards Induction, surely you must admit that the initial part of the task falls not upon the Reason but upon the Imagination; which sees likenesses and leaps to general conclusions, mostly premature or false, but all containing a truth from which the falsehood must be eliminated. Thus, a child imagines, by premature Induction, that all men are (1) like his father; (2) black haired; (3) between five and six feet high; (4) white-skinned, and so on. Then comes Reason afterwards, comparing and contrasting these imaginative premature conclusions with a wider and contradictory experience and widening the conclusion accordingly. Hence it is the part of Reason to suggest those varied experiments which are a necessary part of scientific Induction; and this is generally done by pointing out to us some neglected difference: “You say you had a Turkish bath three times, and each time caught a cold: but were the antecedents of these three colds quite alike? If not, how did they differ? Did you not on the first occasion sit in a draught at a public meeting? on the second, forget to put on your great coat? on the third, let the fire out though it was freezing? Consider therefore, not the single point of likeness, the Turkish bath, but the points of unlikeness also, in the antecedents of your three colds; and try the Turkish bath again, omitting these antecedents, before you say ‘A Turkish bath always gives me cold.’”
You see then that in Induction the positive and suggestive part of the work is done by the Imagination; the negative and eliminative part by Reason.
(ii) As regards Deduction, the business of Reason is to ascertain that the Premises are not only true but also connected in such a way that a conclusion can be drawn from them. But even here Imagination plays a part: for the conclusion of every syllogism (roughly speaking) depends upon the following axiom: “If a is included in b, and b is included in c, then a is included in c; in other words, if a watch is in a box, and the box is in a room, then the watch is in the room.” Now this general proposition, like all general propositions, is arrived at with the aid of the Imagination, so that we may fairly say that the Imagination, helps to lay the foundation of the Syllogism. When therefore you bear in mind that in every Syllogism the Premises are often the result of an Induction in which Imagination has played a part, and that the conclusion always depends upon an axiom of the Imagination, you must admit that even Deductive Reasoning by no means excludes the Imagination.
(iii) Practically, errors seldom arise, and truth is seldom discovered, from mere Deductive Reasoning. Any one can see his way through a logical Syllogism, and almost any one can lay his finger on the weak point in an illogical one. But the difficulty is to start the Reasoning in the right direction and to begin the Logical Chain with an appropriate Syllogism.
For example, suppose we wish to prove that “every triangle which has two angles equal, has two sides opposite to them equal”: how can our Reason, our discriminative faculty, help us here? At present, not at all. We must first call to our aid the Imagination, which says to us, “Imagine the triangle with two equal angles to have two unequal sides opposite to them, and see what follows.” And every one who has done a geometrical Deduction knows that we frequently start by “imagining” the conclusion to be already proved, or the problem to be already performed, and then endeavouring to realise, among the many consequences that would follow, which of those consequences would harmonize with, or be identical with, the data to which we are working back.
The same process is common in the reasoning that deals with what is called Circumstantial Evidence. Thus, it is asserted by A that he saw B commit a murder in the midst of a field, five minutes before midnight, on the first day of last month: how can we test the truth of A’s assertion? The negative faculty of Reason cannot answer the question. But once more Imagination steps in and says, “Imagine the story to be true; imagine yourself to be in A’s place; imagine the circumstances which would have surrounded him, the hidden place from which he saw the murder, the light which enabled him to see it, the precise sight that he saw, the voices or sounds that he heard, and, in a word, all the details of a likely and coherent narrative.” When the Imagination has done this and “imagined” the place—perhaps a hedge—the light—moonlight, and so on, Reason steps in, and corroborates or rejects, by shewing that there was, or was not, a hedge whence the deed could have been witnessed; that there was a full moon or no moon on the night in question; that, if there had been a moon, the place in question was open to the moonlight, or in deep shadow: and thus Imagination and Reason (aided by experience of the place and knowledge of the time) arrive at a conclusion, the former making a positive, the latter a negative contribution. Hence it appears that even in those questions which are called pre-eminently “practical”—for what can be more “practical” than a trial in a law-court for life or death?—the Imagination plays so great a part that without its aid the reason could effect little or nothing.
Here I must break off; but I hope I have said enough to satisfy you that the imaginative faculty, though it needs the constant test of Reason and Experience, is far more intimately connected with what we call knowledge, than is commonly supposed. But if this be so, we ought not (I think) to be surprised if a careful analysis of our profoundest religious convictions should reveal that for these also we are indebted, and intended by God to be indebted, to the Imagination far more than to the Reason.
VII
THE CULTURE OF FAITH
My dear ——,
I have been very much pained by your sprightly account of the lively and witty conversation between you and your clever young friends, —— and ——, on the proofs of the existence of a God. Bear with me if I assure you that discussions in that spirit are likely to be fatal to real faith. They may often be far more dangerous than a serious collision between untrained faith and the most highly educated scepticism. I do not deprecate discussion, but I do most earnestly plead for reverence.