To revert to the starting point of our lives is to seek nature in vain, since the alternations of art and nature proceed relentlessly, whether we rest our dead weight on the process or try to help it along. It is a vain flattery of our reluctance to travel, to take our seat always in the last car. But, however futile, the cult of the natural in literature has a reasonable explanation, and it is well to understand with sympathy why it is likely to recur periodically in a civilization that must feel its age more and more. Art criticizes life, as we have often been told, by selecting or sifting it; that is what the word criticism means. The authority that art has over us, its right to make such a sifting, derives not from books but from the human brain itself, from the method of memory; we remember only by forgetting most of the things we have done or have suffered, and rearranging the rest. As we grow older life becomes clearer, we say, thanks to this selection and forgetting. When art sifts life, then, it is only imitating the process of nature, and when we observe the process we can understand why the Greeks said that memory was the mother of the muses. But this sifting of life on the part of memory and of art is progressive, and in all honesty we may wonder at times whether it has not gone too far. Some of the clarity of vision, the firmness of doctrine, which is the reward of old age, may be not the genuine harvesting of experience which is almost the gift of prophecy; it may be rather a partial memory which seems clear because so much has been left out. If a poet could get a first-hand impression of life, his art would be one sifting of nature; if he reacts not only to nature but to the interpretations of other poets, his art is a second sifting, more highly organized, perhaps, more intelligible, than is normally recorded from immediate contact with life. It makes no difference whether we call these siftings poetry or criticism, since poetry, as Arnold reminded us, is a criticism of life. The poet may submit his sensitiveness to nature as sifted through three or four or any number of interventions of personality, and we may call the result poetry, or criticism, or criticism of criticism; very often we cannot tell, and the poet does not know, whether the life that stimulates him is direct or transmitted. But in each remove from the first contact with nature, in each additional intervention of personality, we get a clearer order and a finer intelligibility—truth instead of facts, formulas instead of experiences, and fewer exceptions. The literature, then, which begins in naturalism will at last emerge in philosophy, if we allow it time enough, and the biography of an individual will be condensed and generalized into a proverb.