The physical and unconscious self-sacrifice of parents to form offspring, which the lowest living things display from hour to hour, shows us in its primitive form the altruism which makes possible the egoism of individual life and growth. As we ascend to higher grades of creatures, this parental altruism becomes a direct yielding up of only part of the body, joined with an increasing contribution from the remainder in the shape of tissue wasted in efforts made on behalf of progeny. This indirect sacrifice of substance, replacing more and more the direct sacrifice as parental altruism becomes higher, continues to the last to represent also altruism which is other than parental; since this, too, implies loss of substance in making efforts that do not bring their return in personal aggrandizement. After noting how among mankind parental altruism and family altruism pass into social altruism, we observed that a society, like a species, survives only on condition that each generation of its members shall yield to the next, benefits equivalent to those it has received from the last. And this implies that care for the family must be supplemented by care for the society. Fullness of egoistic satisfactions in the associated state, depending primarily on maintenance of the normal relation between efforts expended and benefits obtained, which underlies all life, implies an altruism which both prompts equitable conduct and prompts the enforcing of equity. The well-being of each is involved with the well-being of all in sundry other ways. Whatever conduces to their vigor concerns him, for it diminishes the cost of everything he buys. Whatever conduces to their freedom from disease concerns him, for it diminishes his own liability to disease. Whatever raises their intelligence concerns him, for inconveniences are daily entailed on him by others' ignorance or folly. Whatever raises their moral character concerns him, for at every turn he suffers from the average unconscientiousness. Much more directly do his egoistic satisfactions depend on those altruistic activities which enlist the sympathies of others. By alienating those around, selfishness loses the unbought aid they can render; shuts out a wide range of social enjoyments, and fails to receive those exaltations of pleasure and mitigations of pain which come from men's fellow-feeling with those they like. Lastly, undue egoism defeats itself by bringing on an incapacity for happiness. Purely egoistic gratifications are rendered less keen by satiety, even in the earlier part of life, and almost disappear in the later; the less satiating gratifications of altruism are missed throughout life, and especially in that latter part when they largely replace egoistic gratifications; and there is a lack of susceptibility to æsthetic pleasures of the higher orders.