The first thing in the study of human nature is observation of the external part of man. This has two aspects: one is the head of man, and the other is his form. And this can be seen from two points of view: the first is the analytical point of view, and the second is the synthetic. The former is understanding of the character of each organ and the meaning of its form, and the latter is the harmony of the different organs. And a person understands half if he considers one organ only and not its combination with other organs.