“And Socrates, sitting on the side of the bed, bent his leg and rubbed it with his hand, and in doing so said,――'How strange a thing, my friends, is that which is called Pleasure! and how oddly it is connected with what is called Pain! Pleasure and Pain do not come to man together; but if a person runs after the one and catches it, he almost immediately catches the other too, as if they were fastened together at one end. I think if Æsop had noticed this he would have compiled a fable to this effect: That the gods tried to reconcile these two opposites, and not being able to do this, fastened their extremities together so that when you take hold of one it pulls after it the other. And so it happens to me now; there was pain in my leg when the chain bound it, and now comes pleasure following the pain.’” A law of physiology, a law of the whole universe, underlies these homely reflections of the ancient Greek. On the one side, pleasure and pain are states of feeling totally opposed to each other both in sensation and in physical effect, pleasure being concomitant with an increase, pain with a decrease, of the vital functions; and yet, on the other, there is a unity, or, at any rate, a close analogy of action, under these contrary conditions of mental life. Each is a stimulus to new forms of mental change and biotic motion, though in the one instance the tendency of the new activity is toward a higher concentration of the individual life, and, in the other, toward its diminution or its disaggregation into other and lower forms. A feeling of pleasure is an exaltation of sensation in some special set of nerves. These are stimulated to an unwonted exercise of their functions; but they can provide this disproportionate energy only by drafts on the general resources of the nervous system; and this must be paid back through exhaustion, fatigue, or, perhaps, actual pain. A sensation of pain also demands for its presence special and unusual conditions of nervous activity, which also result in exhaustion of the powers of sensation, but, unfortunately, much later than in conditions of pleasure. Pain seems in some sort more our natural element, for we can bear it much longer than pleasure in equal degree. Generalizing on this fact, Schopenhauer reached the dismal conclusion――“The essential elements of all Life are pain and sorrow.” The mere cessation of pain is in itself a pleasure of considerable degree, as in the case of Socrates relieved from the chafing of his irons; indeed, probably some of the intensest moments of delight are those experienced on a sudden relief from acute suffering, or during the reaction from long privations.