Let this suffice as my protest against the popular fallacy that the Imagination is an abnormal faculty, limited to poets and painters and “artists,” mostly illusive, and always to be subordinated in the search after truth. I maintain, on the contrary, that it lies at the basis of all knowledge; that it is no less necessary for science, for morals, and for religion, than for artistic success; and that the illusions of Imagination are the stepping-stones to Truths. Now to speak of Reason, or, as some would call it, Understanding. While dealing with Imagination, we recognized that the work of Reason is mostly negative and corrective: but let us come to detail. Reason is commonly said to proceed by two methods; (i) by Induction, wherein, by “inducing,” or introducing, a number of particular instances (_e.g._ “A, B, C, &c., are men and are mortal”), you establish a general conclusion (“all men are mortal”); (ii) by Deduction, wherein, from two previous statements called Premises, you deduce a third, called a Conclusion. (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.