The process of which these are the outward landmarks went on during the whole period of the Republic, and resulted in the substitution of what may be called with Mommsen the Graeco-Roman, for the old Roman religion. The change was a very profound one. Not only were some new gods added to the old ones, not only did Greek art come to be employed in Roman temples, not only were new rites introduced, such as the _lectisternium_, in which couches were arranged, each with the image of a god and that of a goddess, and tables spread to regale the recumbent deities. The very notion of deity was changed; the Greek god, represented by an image in human form and moving freely in the upper world, was substituted for the Latin god who was the unseen side of an act or process or quality, from which he had his name, and apart from which he was not. The following is a list of the principal Roman gods and of the Greek ones with whom they were identified:--Jupiter (Zeus), Juno (Hera), Neptunus (Poseidon), Minerva (Athene), Mars (Ares), Venus (Aphrodite), Diana (Artemis), Vulcanus (Hephaestus), Vesta (Hestia), Mercurius (Hermes), Ceres (Demeter). The identifications are by no means accurate; Jupiter and Vesta, as we have seen, are the only two Roman gods who are really identical with Greek gods, the other equations are founded on accidental resemblances, and are more arbitrary than real. The result of them was, however, that the Romans forgot to a large extent their own gods, and got Greek ones instead. With the divine figures they took over the mythology of Greece, and thus the gods came to be well known with all their weaknesses, instead of as before surrounded with mystery and awe. The worship founded on the earlier conception of the deity, and kept up with unwavering regularity, was inapplicable to these new gods, and inevitably lost all its reality. This is not the only cause, but it is one of the chief causes which prepared for the fearful spectacle presented by Roman religion at the end of the Republic, when men of learning and distinction officiated as the heads of a religion in which they had no belief, and which they scoffed at in their writings.