Prantl, writing a few years before the appearance of Mr. Darwin’s book on the Origin of Species, and therefore without any prejudice on the subject, observes with truth that this theory of Empedocles was deeply rooted in the mythological conceptions of the time.[23] Perhaps he was seeking for a rationalistic explanation of the centaurs, minotaurs, hundred-handed giants, and so forth, in whose existence he had not, like Lucretius, learned completely to disbelieve. His strange supposition was afterwards freed from its worst extravagances; but even as stated in the _De Rerum Naturâ_, it has no claim whatever to rank as a serious hypothesis. Anything more unlike the Darwinian doctrine, according to which all existing species have been evolved from less highly-organized ancestors by the gradual accumulation of minute differences, it would be difficult to conceive. Every thinker of antiquity, with one exception, believed in the immutability of natural species. They had existed unchanged from all eternity, or had sprung up by spontaneous generation from the earth’s bosom in their present form. The solitary dissentient was Anaximander, who conjectured that man was descended from an aquatic animal.[24] Strange to say, this lucky guess has not yet been quoted as an argument against the Ascidian pedigree. It is chiefly the enemies of Darwinism who are eager to find it anticipated in Empedocles or Lucretius. By a curious inversion of traditionalism, it is fancied that a modern discovery can be upset by showing that somebody said something of the kind more than two thousand years ago. Unfortunately authority has not the negative value of disproving the principles which it supports. We must be content to accept the truths brought to light by observation and reasoning, even at the risk of finding ourselves in humiliating agreement with a philosopher of antiquity.[25]