Thus Darwin defines the general good or welfare which should be the aim of our conduct as "the rearing of the greatest number of individuals in full health and vigour with all their faculties perfect;" upon which Mr. Sidgwick remarks[6] with justice: "Such a reduction of the notion of 'well-being' to 'being' (actual and potential) would be a most important contribution from the doctrine of Evolution to ethical science. But it at least conflicts in a very startling manner with those ordinary notions of progress and development" in which "it is always implied that certain forms of life are qualitatively superior to others, independently of the number of individuals, present or future, in which each form is realized.... And if we confine ourselves to human beings, to whom alone the practical side of the doctrine applies, is it not too paradoxical to assert that 'rising in the scale of existence' means no more than 'developing the capacity to exist'? A greater degree of fertility would thus become an excellence outweighing the finest moral and intellectual endowments; and some semi-barbarous races must be held to have attained the end of human existence more than some of the pioneers and patterns of civilization." Nor is it only in the region of ethics but in every region that this false simplification is fertile in paradoxes; and yet if it be disowned, the charm to which Evolution owes its popularity is gone. It would be indeed a short cut to knowledge if we might believe life to be, as this theory imagines it, a simple, self-diffusing force with an irrepressible tendency to spread itself in all directions, like fire in a prairie. True we should not have altogether got rid of innate tendencies, but we should have reduced them to one, namely, to the struggling, or persisting, or self-asserting tendency; a simplification like that offered by the matter-and-force theory of Buchner.