The History of Rome, by Theodor Mommsen (Etext)
Such was the nature and such the influence of the Roman religion in its pure, unhampered, and thoroughly national development. Its national character was not infringed by the fact that, from the earliest times, modes and systems of worship were introduced from abroad; no more than the bestowal of the rights of citizenship on individual foreigners denationalized the Roman state. An exchange of gods as well as of goods with the Latins in older time must have been a matter of course; the transplantation to Rome of gods and worships belonging to less cognate races is more remarkable. Of the distinctive Sabine worship maintained by the Tities we have already spoken.(14) Whether any conceptions of the gods were borrowed from Etruria is more doubtful: for the Lases, the older designation of the genii (from lascivus), and Minerva the goddess of memory (men, menervare), which it is customary to describe as originally Etruscan, were on the contrary, judging from philological grounds, indigenous to Latium. It is at any rate certain, and in keeping with all that we otherwise know of Roman intercourse that the Greek worship received earlier and more extensive attention in Rome than any other of foreign origin. The Greek oracles furnished the earliest occasion of its introduction. The language of the Roman gods was on the whole confined to Yea and Nay or at the most to the making their will known by the method of casting lots, which appears in its origin Italian;(15) while from very ancient times -- although not apparently until the impulse was received from the East -- the more talkative gods of the Greeks imparted actual utterances of prophecy. The Romans made efforts, even at an early period, to treasure up such counsels, and copies of the leaves of the soothsaying priestess of Apollo, the Cumaean Sibyl, were accordingly a highly valued gift on the part of their Greek guest-friends from Campania. For the reading and interpretation of the fortune-telling book a special college, inferior in rank only to the augurs and Pontifices, was instituted in early times, consisting of two men of lore (duoviri sacris faciundis), who were furnished at the expense of the state with two slaves acquainted with the Greek language. To these custodiers of oracles the people resorted in cases of doubt, when an act of worship was needed in order to avoid some impending evil and they did not know to which of the gods or with what rites it was to be performed. But Romans in search of advice early betook themselves also to the Delphic Apollo himself. Besides the legends relating to such an intercourse already mentioned,(16) it is attested partly by the reception of the word thesaurus so closely connected with the Delphic oracle into all the Italian languages with which we are acquainted, and partly by the oldest Roman form of the name of Apollo, Aperta, the "opener," an etymologizing alteration of the Doric Apellon, the antiquity of which is betrayed by its very barbarism. The Greek Herakles was naturalized in Italy as Herclus, Hercoles, Hercules, at an early period and under a peculiar conception of his character, apparently in the first instance as the god of gains of adventure and of any extraordinary increase of wealth; for which reason the general was wont to present the tenth of the spoil which he had procured, and the merchant the tenth of the substance which he had obtained, to Hercules at the chief altar (ara maxima) in the cattle-market. Accordingly he became the god of mercantile covenants generally, which in early times were frequently concluded at this altar and confirmed by oath, and in so far was identified with the old Latin god of good faith (deus fidius). The worship of Hercules was from an early date among the most widely diffused; he was, to use the words of an ancient author, adored in every hamlet of Italy, and altars were everywhere erected to him in the streets of the cities and along the country roads. The gods also of the mariner, Castor and Polydeukes or, in Roman form, Pollux, the god of traffic Hermes -- the Roman Mercurius -- and the god of healing, Asklapios or Aesculapius, became early known to the Romans, although their public worship only began at a later period. The name of the festival of the "good goddess" (bona dea) damium, corresponding to the Greek -- damion -- or -- deimion -- , may likewise reach back as far as this epoch. It must be the result also of ancient borrowing, that the old Liber pater of the Romans was afterwards conceived as "father deliverer" and identified with the wine-god of the Greeks, the "releaser" (Lyaeos), and that the Roman god of the lower regions was called the "dispenser of riches" (Pluto - Dis pater), while his spouse Persephone became converted at once by change of the initial sound and by transference of the idea into the Roman Proserpina, that is, "germinatrix." Even the goddess of the Romano-Latin league, Diana of the Aventine, seems to have been copied from the federal goddess of the lonians of Asia Minor, the Ephesian Artemis; at least her carved image in the Roman temple was formed after the Ephesian type.(17) It was in this way alone, through the myths of Apollo, Dionysus, Pluto, Herakles, and Artemis, which were early pervaded by Oriental ideas, that the Aramaic religion exercised at this period a remote and indirect influence on Italy. We clearly perceive from these facts that the introduction of the Greek religion was especially due to commercial intercourse, and that it was traders and mariners who primarily brought the Greek gods to Italy.
These individual cases however of derivation from abroad were but of secondary moment, while the remains of the natural symbolism of primeval times, of which the legend of the oxen of Cacus may perhaps be a specimen,(18) had virtually disappeared. In all its leading features the Roman religion was an organic creation of the people among whom we find it.