How do we gain knowledge about motives, the moving powers of the human machine? Since we cannot take this machinery to pieces, or experiment with it freely, we must derive our knowledge largely from the consciousness of our own motives. Tickling produces laughter in us, and pricking, a cry; affection, and the command of those whom we love, produce in us obedience; desire of a result or reward produces effort; fear of pain or penalty produces avoidance of certain actions, performance of others. Hence we infer that, in others also, similar effects have been produced, or will be produced, by similar causes. In either case, our inference is based partly upon our observation that these causes have preceded these effects in other persons, and partly upon our _faith_ that other people’s machinery is like our own. But we have not yet touched one of the most powerful of motives, that power within us which we call Conscience (“joint-knowledge”); as though there were in us an Assessor sitting in judgment by the side of the mysterious “I,” the two together pronouncing sentence of “Right” or “Wrong” upon the several propositions and intentions which are, as it were, called up before their tribunal. The development of Conscience and our sensibility to its dictation appears to me largely due to the Imagination. If a philosopher tells me that when Conscience appears to us to say “Right” it really says “Expedient for society and ultimately for yourself,” or “Calculated to gain esteem for yourself,” or “Conducive to your own peace of mind,” I am obliged, with all deference to him, but with greater deference to truth, to assure him that (however correct he may be as to the origin of this feeling in my own infant mind or in the matured mind of my primæval ancestors) he is mistaken, at all events in my own case, as to the action of Conscience now. I may possibly have been long ago guided to my idea of “Right” by my observation of what is expedient: but, to me, now, the sense of “right” is as different from the sense of “expedient,” as the eye is different from some sensitive protuberance which may ultimately be developed into an eye, but is at present responsive only to the touch.