consider the question of why beings should live, or should desire to live; or why there are agreeable and useful variations which the being should mate an effort to preserve. Now, external selection evidently presupposes an internal spring, of necessity or spontaneity, which produces, with life, the bound toward a higher life, the bound of evolution. A German biologist, Mr. Rolph, looked for this spring in the movement of assimilation by endosmose, which is characteristic of all organized beings, or of all individual cells, and which he assumed to be insatiable. In this view, we might then speak of a "mechanical hunger," or craving, as the cause of all the actions of living organisms. Corresponding with this "mechanical hunger" appears, at a particular stage of evolution, what Mr. Rolph calls "psychical hunger," which makes itself felt at first essentially as pain; while pleasure is only "a secondary and derivative phenomenon." Hence it results that pain is the motive spring of the universe. This theory is intimately connected with the doctrine which assumes that the essence of pleasure, or at least its necessary condition, is the suppression of pain. Leibnitz has mentioned those infinitesimal and imperceptible "little griefs" which, being suppressed, give "a quantity of half-pleasures," the continuation and accumulation of which, "as in the continuation of the impulsion of a grave body, which gains impetuosity as it falls," become at last a real and whole pleasure. "And at the bottom," he adds, "without these half-griefs there would be no pleasure, and we should have no means of perceiving that anything aids and relieves us by removing the obstacles that hinder our setting ourselves at ease." An Italian philosopher of the eighteenth century, Verri, developing Leibnitz's thought, came to the conclusion that a pain precedes every pleasure; and the theory has been followed up by Kant and Schopenhauer and the pessimists.
To resolve this question which the pessimists have raised, we must inquire whether there are any pleasures that make themselves felt directly, without the intervention of a previous pain; and whether there can be motives to activity without the assistance of pain. It appears to us that the pleasures of the higher senses, of sight, hearing, and smell, and the mental pleasures, and those of science and art, belong to the latter category. A child, seeing a scarlet cloth for the first time, gains an excitation of the sense of sight which is in no way the suppression of a previous pain. To invoke in this case imperceptible uneasiness and latent wants, and a tension of the optic nerve aspiring to fulfill them, is to form a hypothesis which has a part of truth, but does not wholly explain the phenomena. The pleasure here is not simply the exact filling of a void, or the adequate satisfaction of a pre-existing want; it is a surplus, an addition. If we regard the scale of intensities in sensation, we shall find that there is a point near to indifference, departing from which some pleasures are capable of arising by an increase of intensity. Not every pleasure supposes a previous
