A people so endowed were the natural creators of philosophy. There came a time when the harmonious universality of the Hellenic genius sought for its counterpart and completion in a theory of the external world. And there came a time, also, when the decay of political interests left a large fund of intellectual energy, accustomed to work under certain conditions, with the desire to realise those conditions in an ideal sphere. Such is the most general significance we can attach to that memorable series of speculations on the nature of things which, beginning in Ionia, was carried by the Greek colonists to Italy and Sicily, whence, after receiving important additions and modifications, the stream of thought flowed back into the old country, where it was directed into an entirely new channel by the practical genius of Athens. Thales and his successors down to Democritus were not exactly what we should call philosophers, in any sense of the word that would include a Locke or a Hume, and exclude a Boyle or a Black; for their speculations never went beyond the confines of the material universe; they did not even suspect the existence of those ethical and dialectical problems which long constituted the sole object of philosophical discussion, and have continued since the time when they were first mooted to be regarded as its most peculiar province. Nor yet can we look on them altogether or chiefly as men of science, for their paramount purpose was to gather up the whole of knowledge under a single principle; and they sought to realise this purpose, not by observation and experiment, but by the power of thought alone. It would, perhaps, be truest to say that from their point of view philosophy and science were still undifferentiated, and that knowledge as a universal synthesis was not yet divorced from special investigations into particular orders of phenomena. Here, as elsewhere, advancing reason tends to reunite studies which have been provisionally separated, and we must look to our own contemporaries—to our Tyndalls and Thomsons, our Helmholtzes and Zöllners—as furnishing the fittest parallel to Anaximander and Empedocles, Leucippus and Diogenes of Apollonia.