The instinct of conservation is, as we have seen, a collective term, an abridged formula, used to designate the totality of particular tendencies which assure the persistence of the individual, and one of which, the craving for food, is fundamental. It manifests itself in all its simplicity in most animals and in savage tribes who live, strictly speaking, from day to day. Yet ants, bees, foxes, and many other animals put aside a reserve store of food for future needs. The human race has very rapidly acquired the habits of foresight and care for the future, even while still in the savage stage and living by hunting and fishing. With a nomadic or agricultural life, the need of possession affirms itself more and more. As social progress substitutes for exchanges in kind the use of the precious metals, first in ingots, then as coined money, and later still, of paper money, feeling follows the same course, transferring itself from things to the values which represent them and the representations of these values, in many cases with well-known tenacity; and we see people who prefer illness to the expense of a cure, the risk of being murdered to the unpleasantness of giving up their purses. So that those values and signs of values which represent the possibility of satisfying needs (food, clothes, lodging, etc.), become in and for themselves a cause of desire and pleasure, and, amassed as a security for life, remain useless—if, indeed, they do not cause death. Avarice is a passion very well suited to illustrate this evolution in heterogeneous form, which, in spite of a strictly logical development, undergoes so many changes that its extreme point seems the negation of its point of departure. The feeling of strength, self-feeling in its positive form, is at first, as we have seen, the consciousness of physical energy; but, with the intellectual development, it radiates in different directions, according to temperament and disposition. We can at least note two very different directions: (1) an evolution in the theoretical and purely individual sense, which leads a man to take up all questions, examine and criticise everything, form an independent opinion on every subject—in short, to have as his ideal an absolute liberty of thought, without any sort of restriction; (2) an evolution in the practical and social sense, extending one’s power over things and men; the child who domineers over his playmates may, at a later age, impose his personality on a party, a nation, a number of nations (Cæsar, Napoleon). The quality of the emotions felt in the two cases is very different; however, the original source is common to both, the divergence is the effect of character and intellectual evolution. II.