A passage of Cicero’s _Tusculans_,[364] which is directly inspired by the _Phaedo_ of Plato, is instructive as to the transformation which ideas underwent. “There are,” it says, “two roads and two courses for souls which issue from the body. The souls which are sullied with human vice and have abandoned themselves to passions ... follow a crooked path which leads them away from the dwelling of the gods; but for the souls which have kept their innocence and purity and have, while in human bodies, imitated the life of the gods, there is an easy return to the beings from whose abode they descended to the earth.” In the same way Virgil, as we have said elsewhere,[365] is apparently faithful to the traditional topography of Hades, but does not regard it as really situated in the underground. There were even attempts to fix precisely the itinerary which souls had to follow in the upper spheres. Seneca pleasantly ridicules these beliefs in his satire on the apotheosis of Claudius, affirming that emperors went to heaven by the Appian Way. The Milky Way, originally regarded as the path of the sun, remained, according to an opinion which persisted until the end of antiquity, the road by which gods and heroes rose to the zenith.[366] It was said to cut the zodiac in the tropical signs of Cancer and Capricorn, and it was there that those gates opened by which souls went down from heaven to earth and rose from earth to heaven.[367] The former of these gates was called the Gate of Men, the other the Gate of Gods. We will return later (p. 162) to the theories which assign different dwellings in the starry spheres to pure spirits and tell of their passing through the celestial gates. We would merely note that the allegory of the two roads, of which one is the road of God and heaven and eternal life and the other that of Satan, hell and death, is found in the most ancient Christian literature, and is justifiably likened by Lactantius[368] to the Pythagorean Y, which is at the origin of all the later symbolism. * * * * * But when the idea of a journey to the underworld had been transformed into that of a journey to heaven, how was the power of the dead to reach the upper spheres explained? What force or what vehicle raised them thither? Originally they made use of all the means of locomotion. They went on foot, in a ship, in a carriage, on horseback, and even had recourse to aviation.