The moral end has sometimes been defined as social vitality. Vitality is, in strictness, the energy to live, and has two aspects. It is (1) the force which keeps a creature alive, or (2) the force which keeps it well. As implying the keeping up of vital functions, the notion of continued existence represents the end, but represents it in its lowest aspect, its least and poorest significance, and is an insufficient description; for not existence can be the end, but existence of a certain sort. "Existence, in fact, is an abstraction to which nothing corresponds in experience: nothing exists except upon certain terms. Given the type, the end of the creature is to continue the existence of that type; but continuance of existence is nothing more nor less than the performance of those functions which constitute the type of life in question: it is not separated from those functions as something which they subserve." If the functions in man or animal are said to be determined by the need of maintaining his existence, it may be answered that his existence is these functions. In this sense of continued existence as the repetition of vital functions in their order, it is true, but only secondarily true, that the end is to preserve life. But the doctrine of evolution implies much more than such preservation. It means the victorious continuance of life. But because a type is victorious, we cannot infer that the end of the type is to maintain its victorious existence in the sense of aiming at victory. To do this is to read into the end a theory of how the type came into existence. The end of a type is to act according to the type; the victory over rivals affords the opportunity of this. The preservation of existence is a condition of the end, not the end itself; to regard it as such is to confuse cause with effect. Vitality as health, on the other hand, implies the equilibrium which constitutes good conduct good. It must, however, "be observed that health is not a further specification or a limitation of continued life, but is coextensive with it." But health, as applied to morals, is a metaphorical term. Morality does not consist in mere physical vitality; on the contrary, some sacrifice of such vitality may be necessary, the perfect physical vitality may be inconsistent with the development of higher and finer mental functions. "With this proviso, vitality as health is simply another name for the character of good conduct which wins it the title of good."