The fundamental idea on which it rests, the idea that the psychic essence is the same as the fire of the heavenly bodies, is at the root of all oriental astrology, which claims to explain by astral influence the formation of character. This idea of a relationship (συγγένεια) between the soul and the stars does not in Greece belong to the old basic popular beliefs. It was introduced thither by the philosophers, who, as we shall see, drew from it very important theological conclusions. According to them, it was owing to this identity of nature that the soul was capable of knowing the gods and of aspiring to join them.[229] This doctrine took on new power when astrology succeeded in imposing itself on the Alexandrian world, and it is significant that we find it clearly formulated by an adept of this pseudo-science, the famous Hipparchus, in the second century before our era. “Hipparchus,” says Pliny,[230] “will never receive all the praise he deserves, since no one has better established the relation between man and the stars, or shown more clearly that our souls are particles of the heavenly fire.” Pythagorism and Stoicism, and after them the Syrian and Persian mysteries, were to popularise this conception throughout the ancient world. In certain regions, as in Gaul, it undoubtedly found pre-existing native beliefs with which it combined, and in religion and among theologians it assumed multiple forms. We shall try to distinguish its chief aspects, dealing successively with lunar, solar and stellar immortality. * * * * * The Pythagoreans, perhaps transforming a belief of the Greek people as to Selene’s rôle, but more probably inspired by Oriental speculations, held that souls, when they had been purified by air, went to dwell in the moon. To the question, “What are the Isles of the Blessed?” the orthodox doctrine of the sect answered, “The sun and the moon.”[231] For them the heavenly bodies were moving islands washed by a luminous fluid, which their swift motion caused to sound about them. These thinkers, who debated all the scientific hypotheses, accepted the plurality of worlds. The heavenly bodies were other earths surrounded by air and rolling in the boundless ether. The moon in particular was designated as the “ethereal” or “Olympic earth,” and in the moon lay the Elysian Fields, the meadows of Hades, in which the shades of the heroes rested. Pythagoras himself, promoted to the rank of an immortal spirit, rejoiced there among the sages. Persephone, assimilated to Artemis, reigned over this kingdom. Did not the moon, like her, transfer itself alternately above and below the earth? The planets were this huntress’s hounds which, ever in chase, were scouring the fields of space around her in every direction.