The world in general is attracted by similarity of form, but remains indifferent to similarity of understanding. The creature that has a long skeleton, hands differently shaped from the feet, hair on its head, and an even set of teeth in its jaws, and walks erect, is called a man. But it does not follow that a man may not have the mind of a brute. Even though this be the case, other men will still recognize him as one of their own species in virtue of his outward form. In infancy, the vital force is concentrated, the will is simple, and the general harmony of the system is perfect.
External objects produce no injurious impression, and to the moral nature nothing can be added.
In adolescence, the animal passions are wildly exuberant, the heart is filled with rising desires and preoccupations. The man is open to attack by the objects of sense, and thus his moral nature becomes enfeebled. In old age, his desires and preoccupations have lost their keenness, and the bodily frame seeks for repose. External objects no longer hold the first place in his regard. In this state, though not attaining to the perfection of infancy, he is already different from what he was in adolescence.