The mechanical organization of external nature is thus the source of apperceptive forms in the mind. Did not sensation, by a constant repetition of certain sequences, and a recurring exactitude of mathematical relations, keep our fancy clear and fresh, we should fall into an imaginative lethargy. Idealization would degenerate into indistinctness, and, by the dulling of our memory, we should dream a world daily more poor and vague. This process is periodically observable in the history of the arts. The way in which the human figure, for instance, is depicted, is an indication of the way in which it is apperceived. The arts give back only so much of nature as the human eye has been able to master. The most primitive stage of drawing and sculpture presents man with his arms and legs, his ten fingers and ten toes, branching out into mid-air; the apperception of the body has been evidently practical and successive, and the artist sets down what he knows rather than any of the particular perceptions that conveyed that knowledge. Those perceptions are merged and lost in the haste to reach the practically useful concept of the object. By a naive expression of the same principle, we find in some Assyrian drawings the eye seen from the front introduced into a face seen in profile, each element being represented in that form in which it was most easily observed and remembered. The development of Greek sculpture furnishes a good example of the gradual penetration of nature into the mind, of the slowly enriched apperception of the object. The quasi-Egyptian stiffness melts away, first from the bodies of the minor figures, afterwards of those of the gods, and finally the face is varied, and the hieratic smile almost disappears.[10] But this progress has a near limit; once the most beautiful and inclusive apperception reached, once the best form caught at its best moment, the artist seems to have nothing more to do. To reproduce the imperfections of individuals seems wrong, when beauty, after all, is the thing desired. And the ideal, as caught by the master's inspiration, is more beautiful than anything his pupils can find for themselves in nature. From its summit, the art therefore declines in one of two directions. It either becomes academic, forsakes the study of nature, and degenerates into empty convention, or else it becomes ignoble, forsakes beauty, and sinks into a tasteless and unimaginative technique. The latter was the course of sculpture in ancient times, the former, with moments of reawakening, has been its dreadful fate among the moderns.