There is no function of our nature which cannot contribute something to this effect, but one function differs very much from another in the amount and directness of its contribution. The pleasures of the eye and ear, of the imagination and memory, are the most easily objectified and merged in ideas; but it would betray inexcusable haste and slight appreciation of the principle involved, if we called them the only materials of beauty. Our effort will rather be to discover its other sources, which have been more generally ignored, and point out their importance. For the five senses and the three powers of the soul, which play so large a part in traditional psychology, are by no means the only sources or factors of consciousness; they are more or less external divisions of its content, and not even exhaustive of that. The nature and changes of our life have deeper roots, and are controlled by less obvious processes. The human body is a machine that holds together by virtue of certain vital functions, on the cessation of which it is dissolved. Some of these, like the circulation of the blood, the growth and decay of the tissues, are at first sight unconscious. Yet any important disturbance of these fundamental processes at once produces great and painful changes in consciousness. Slight alterations are not without their conscious echo: and the whole temper and tone of our mind, the strength of our passions, the grip and concatenation of our habits, our power of attention, and the liveliness of our fancy and affections are due to the influence of these vital forces. They do not, perhaps, constitute the whole basis of any one idea or emotion: but they are the conditions of the existence and character of all. Particularly important are they for the _value_ of our experience. They constitute health, without which no pleasure can be pure. They determine our impulses in leisure, and furnish that surplus energy which we spend in play, in art, and in speculation. The attraction of these pursuits, and the very existence of an aesthetic sphere, is due to the efficiency and perfection of our vital processes. The pleasures which they involve are not exclusively bound to any particular object, and therefore do not account for the relative beauty of things. They are loose and unlocalized, having no special organ, or one which is internal and hidden within the body. They therefore remain undiscriminated in consciousness, and can serve to add interest to any object, or to cast a general glamour over the world, very favourable to its interest and beauty.