The force of this long tradition has been broken, however, by two influences of great weight in recent times, the theory of evolution and the revival of pantheism. The first has reintroduced flux into the conception of existence and the second into the conception of values. If natural species are fluid and pass into one another, human nature is merely a name for a group of qualities found by chance in certain tribes of animals, a group to which new qualities are constantly tending to attach themselves while other faculties become extinct, now in whole races, now in sporadic individuals. Human nature is therefore a variable, and its ideal cannot have a greater constancy than the demands to which it gives expression. Nor can the ideal of one man or one age have any authority over another, since the harmony existing in their nature and interests is accidental and each is a transitional phase in an indefinite evolution. The crystallisation of moral forces at any moment is consequently to be explained by universal, not by human, laws; the philosopher’s interest cannot be to trace the implications of present and unstable desires, but rather to discover the mechanical law by which these desires have been generated and will be transformed, so that they will change irrevocably both their basis and their objects. [Sidenote: Pantheism.] To this picture of physical instability furnished by popular science are to be added the mystical self-denials involved in pantheism. These come to reinforce the doctrine that human nature is a shifting thing with the sentiment that it is a finite and unworthy one: for every determination of being, it is said, has its significance as well as its origin in the infinite continuum of which it is a part. Forms are limitations, and limitations, according to this philosophy, would be defects, so that man’s only goal would be to escape humanity and lose himself in the divine nebula that has produced and must invalidate each of his thoughts and ideals. As there would be but one spirit in the world, and that infinite, so there would be but one ideal and that indiscriminate. The despair which the naturalist’s view of human instability might tend to produce is turned by this mystical initiation into a sort of ecstasy; and the deluge of conformity suddenly submerges that Life of Reason which science seemed to condemn to gradual extinction. [Sidenote: Instability in existences does not dethrone their ideals.]