[Sidenote: The inevitable tendency is to the Ionic philosophy.] Not only thus from their intrinsic nature, but also from their recorded gradual development, are we warranted in imputing to the greater part of the myths an indigenous origin. The theogony of Homer is extended by Hesiod in many essential points. He prefixes the dynasty of Uranos, and differs in minor conceptions, as in the character of the Cyclops. The Orphic theogony is again another advance, having new fictions and new personages, as in the case of Zagreus, the horned child of Jupiter by his own daughter Persephone. Indeed, there is hardly one of the great and venerable gods of Olympus whose character does not change with his age, and, seen from this point of view, the origin of the Ionic philosophy becomes a necessary step in the advance. That philosophy, as we shall soon find, was due not only to the expansion of the Greek intellect and the necessary improvement of Greek morals; an extraneous cause, the sudden opening of the Egyptian ports, 670 B.C., accelerated it. European religion became more mysterious and more solemn. European philosophy learned the error of its chronology, and the necessity of applying a more strict and correct standard of evidence for ancient events. It was an ominous circumstance that the Ionian Greeks, who first began to philosophize, commenced their labours by depersonifying the elements, and treating not of Zeus, Poseidon, and Hades, but of Air, Water, Fire. The destruction of theological conceptions led irresistibly to the destruction of religious practices. To divinities whose existence he denied, the philosopher ceased to pray. Of what use were sacrificial offerings and entreaties directed to phantasms of the imagination? but advantages might accrue from the physical study of the impersonal elements. [Sidenote: Inevitable destruction of Greek religious ideas] Greek religion contained within itself the principles of its own destruction. It is for the sake of thoroughly appreciating this that I have been led into a detail of what some of my readers may be disposed to regard as idle and useless myths. Two circumstances of inevitable occurrence insured the eventual overthrow of the whole system; they were geographical discovery and the rise of philosophical criticism. Our attention is riveted by the fact that, two thousand years later, the same thing again occurred on a greater scale. [Sidenote: by geographical discovery.]