that its constancy, in his opinion, was the source of all natural as well as moral laws. Had he doubted for a moment the stability of human nature, the foundations of his system would have fallen out; the forms of perception and thought would at once have lost their boasted necessity, since to-morrow might dawn upon new categories and a modified a priori intuition of space or time; and the avenue would also have been closed by which man was led, through his unalterable moral sentiments, to assumptions about metaphysical truths.
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 transi-