Contrasting sensation and emotion, on the one side, with intellect on the other, feeling with thought, they are seen to be polar or antithetical manifestations of mind. Each requires the other for its existence, yet in such wise that the one is developed at the expense of the other. The one waxes as the other wanes. This is seen to advantage when their most similar elements are compared. Thus consciousness in sensation is keenest when impressions are strongest; but this consciousness is a bar to intellectual self-consciousness, as was pointed out by Professor Ferrier in his general Law of consciousness.[20-1] When emotion and sensation are at their minimum, one is most conscious of the solidarity of one’s thoughts; and just in proportion to the vividness of self-consciousness is thought lucid and strong. In an ideal intelligence, self-consciousness would be infinite, sensation infinitesimal. Yet there is a parallelism between feeling and thought, as well as a contrast. As pain and pleasure indicate opposite tendencies in the forces which guide sensation and emotion, so do the true and the untrue direct thought, and bear the same relation to it. For as pain is the warning of death, so the untrue is the detrimental, the destructive. The man who reasons falsely, will act unwisely and run into danger thereby. To know the truth is to be ready for the worst. Who reasons correctly will live the longest. To love pleasure is not more in the grain of man than to desire truth. “I have known many,” says St. Augustine, “who like to deceive; to be deceived, none.” Pleasure, joy, truth, are the respective measures of life in sensation, emotion, intellect; one or the other of these every organism seeks with all its might, its choice depending on which of these divisions of mind is prominently its own. As the last mentioned is the climax, truth presents itself as in some way the perfect expression of life. We have seen what pleasure is, but what is truth? The question of Pilate remains, not indeed unanswered, but answered vaguely and discrepantly.[21-1] We may pass it by as one of speculative interest merely, and turn our attention to its practical paraphrase, what is true? The rules of evidence as regards events are well known, and also the principles of reaching the laws of phenomena by inductive methods. Many say that the mind can go no further than this, that the truth thus reached, if not the highest, is at least the highest for man. It is at best relative, but it is real. The correctness of this statement may be tested by analyzing the processes by which we acquire knowledge.