and its victory in the struggle for life are connected with the brute quantity of nervous excitation, independently of its quality. But this view involves difficulties. How, for example, can we explain the fact that some sounds and some odors are disagreeable in all their degrees? Again, fix your eyes upon a moderately lighted white surface; you will feel neither fatigue nor displeasure, but you will also experience only a weak positive pleasure. Substitute a blue surface for the white one. The blue ray, which was previously present in the white light as one of its constituent elements, is now offered separately to your eye, with the other rays eliminated, and your pleasure is increased. The increase of pleasure can not be due to an increase of stimulus, for the physical stimulus has been in fact diminished by the quantity of light that has been eliminated. Your pleasure is no more due to a diminution of fatigue, for there was nothing fatiguing about the white. The agreeable nature of the blue is therefore associated with the mode rather than with the degree of nervous action. An effect of heredity and selection is also involved. Animated beings have for many ages received the blue rays from the sky under which they lived, and they have become hereditarily accustomed and adapted to this luminous medium of clear days as well as to the green rays of the fields and woods. It is, however, impossible to account for the details of our sensory pleasures any more than for our æsthetic pleasures. All that can be said is, generally, that the form or quality of the excitation must be taken account of, as well as its quantity.
If we examine the directions toward which the movements of the organisms ultimately tend, we shall find that some tend to the preservation of the substance, others to its destruction; some to life, others to death. Pleasure is of victory in the struggle, of life, pain of defeat, of death. All suffering is a partial death which comes upon some organ or function. Darkness makes us sad because it extinguishes the sight; discords, because the jangle of noises afflicts our perception of sounds. Thus, everything that tends to obstruct and annul a function of the senses produces annoyance and pain. So with mental functions. We enjoy what we can understand clearly, for it implies life and vigor of thought; we are pained when we fail to understand anything clearly, because that conveys an impression of impotency of thought. The emotion of the sublime involves a mingling of sorrow and joy, because, in the immensity of that which excites it, the possibility of perceiving the whole, of comprehending it all in our eye or even in our imagination, is taken away from us; but, by a superior effort, we conceive the infinite, and annul the material obstacle by the power of thought. We thus, at the same time, feel a physical inferiority that depresses us, and a moral superiority that raises us: we die in the world of sense, and are born again in the world of mind.
While Darwin discusses the struggle for existence, he does not
