It was in this epoch of declining energy and declining freedom that there grew up the nugatory doctrine, associated with the Eleatic school, [525] that the only realities are mental, [526] a formula which eluded at once the problems of Nature and the crudities of religion, and so made its fortune with the idle educated class. Meant to support the cause of reason, it was soon turned, as every slackly-held doctrine must be, to a different account. In the hands of Plato it developed into the doctrine of ideas, which in the later Christian world was to play so large a part, as "Realism," in checking scientific thought; and in Greece it fatally fostered the indolent evasion of research in physics. [527] Ultimately this made for supernaturalism, which had never been discarded by the main body even of rationalizing thinkers. [528] Thus the geographer and historian Hekataios of Miletos (fl. 500 B.C.), living at the great centre of rationalism, while rejecting the mass of Greek fables as "ridiculous," and proceeding in a fashion long popular to translate them into historical facts, yet affected, in the poetic Greek fashion, to be of divine descent. [529] At the same time he held by such fables as that of the floating island in the Nile and that of the supernormal Hyperboreans. This blending of old and new habits of mind is indeed perhaps the strongest ground for affirming the genuineness of his fragments, which has been disputed. [530] But from his time forward there are many signs of a broad movement of criticism, doubt, inquiry, and reconstruction, involving an extensive discussion of historical as well as religious tradition. [531] There had begun, in short, for the rapidly-developing Greeks, a "discovery of man" such as is ascribed in later times to the age of the Italian Renaissance. In the next generation came the father of humanists, Herodotos, who implicitly carries the process of discrimination still further than did Hekataios; while Sophocles [496-405 B.C.], without ever challenging popular faith, whether implicitly as did Æschylus, or explicitly as did Euripides, "brought down the drama from the skies to the earth; and the drama still follows the course which Sophocles first marked out for it. It was on the Gods, the struggles of the Gods, and on destiny that Æschylus dwelt; it is with man that Sophocles is concerned." [532]