There were at this time two peoples in Italy, who by reason of their older culture were able to be Rome's teachers. One lay to the north of her, the mysterious Etruscans, whose culture fortunately for Rome had only a very moderate influence, because the Etruscan culture had already lost much of its virility, possibly also because it was distinctly felt to be foreign, and hence could effect no insidious entry, and probably because Rome was at this time too strong and young and clean to take anything but the best from Etruria. The other lay to the south, the Greek colonies of Magna Graecia, separated from Rome for the present by many miles of forest and by hostile tribes. Around her in Latium were her own next of kin, the Latins, becoming rapidly inferior to her, but enabled to do her at least this service, that of absorbing the foreign influences which came, and in certain cases latinising them, and thus transmitting them to Rome in a more or less assimilated condition.
The three great facts in the life of Rome during this period are the coming of Greek merchants and Greek trade from the south, the coming of Etruscan artisans and handicraft from the north, and the beginnings of her political rivalry and gradual prominence in the league of Latin cities around her. Each one of these movements is reflected in the religious changes of the period. In regard to the first two this is not surprising, for the ancient traveller, like his mythical prototype Aeneas, carried his gods with him. Thus there were worshipped in private in Rome the gods of all the peoples who settled within her walls, and the presence of these gods was destined to make its influence felt. Your primitive polytheist is very catholic in his religious tastes; for, when one is already in possession of many gods, the addition of a few more is a minor matter, especially when, as was now the case in Rome, these deities are the patrons of occupations and interests hitherto entirely unknown to the Roman, and hence not provided for in his scheme of gods. It was therefore in no spirit of disloyalty to the already existing gods, and with no desire to introduce rival deities, that the new cults began to spread until they became so important as to call for state recognition.
Possibly the most interesting cases are those of the two gods who came from the south, Hercules and Castor, interesting because they were the forerunners of that great multitude of Greek gods who later came in proudly by special invitation, and even more interesting yet because, though they were Greek as Greek could be, they came into Rome, as it were, incognito, and were so far from being known as Greek, that, when the same gods came in afterwards more directly, these new-comers were felt to be quite a different thing, and their worship was carried on in another part of the city away from the old-established cults.
In the Greek world Herakles and Hermes were the especial patrons of travellers, and as travelling was never done for pleasure but always for business, they became the patrons of the travelling merchant. It was also natural that they should go with the settlers away from the mother-city into the new colony. Thus it was that they came from the mother-land into the colonies of Magna Graecia in Southern Italy, and once being established there made their way slowly but inevitably northwards. The story of Hermes, under the name of Mercury, belongs to a later chapter, but that of Herakles = Hercules must be recounted here. It is only within the last few years that the scholarly world has been persuaded that there was no such thing as an original Italic Hercules; at first sight it was very difficult to believe, because there seemed to be so many apparently very old Italic legends centering in Hercules. But it has been shown, either that these legends never existed and rest solely upon false interpretation of monuments, or that, though they did exist at an early date, they were introduced under Greek influence. It was the trading merchant therefore who brought Herakles northward. And as the god went, his name was softened into Hercules, and with the assimilation of the name to the tongue of the Italic people, there went hand in hand an adaptation of his nature to their needs, so that by degrees he became thoroughly italicised both in form and content. It is probable that the cult came into Rome as well as into the other cities of Latium, but in Rome it was confined to a few individuals, and at first obtained no public recognition. On the contrary, for reasons that we are at a loss to find, this Greek cult seems to have reached very large proportions in the little town of Tibur (Tivoli), fourteen miles north-east of Rome. There it dominated all other worship and lost so much of its foreign atmosphere that it became thoroughly latinised. In the course of time the Roman state acknowledged this Tivoli cult of Hercules and accepted a branch of it as its own. But the extraordinary thing about this acknowledgment is that the Romans felt it to be a Latin and not a foreign cult. They showed this intimate and friendly feeling by permitting an altar to Hercules to be erected within the city proper, in the Forum Boarium. But in order to understand the significance of this act a word of digression is necessary.
Under the old Roman regime every act of life was performed under the supervision of the gods, and this godly patronage was especially emphasised in acts which affected the life of the community. No act was of greater importance for the community than the choice of a home, the location of a settlement. Thus the founding of an ancient city was accompanied by sacred rites, chief among which was the ploughing of a furrow around the space which was ultimately to be enclosed by the wall. This furrow formed a symbolic wall on very much the same principle as that on which the witch draws her circle. The furrow was called the pomerium and was to the world of the gods what the city wall was to the world of men. It did not however always coincide with the actual city wall, and the space it embraced was sometimes less, sometimes more, than that embraced by the city wall; and just as new walls covering larger territory could be built for the city, so a new pomerium line could be drawn. As was becoming for a spiritual barrier there was nothing to mark it except the boundary stones through which the imaginary line passed. The wall, which Servius built and which continued to be the outer wall of Rome for a period of eight or nine hundred years until the third Christian century, was at the time of its building coincident in the main with the line of the pomerium, with one very important exception: namely that all the region of the Aventine, which was inside the limits of the political city and embraced by the Servian wall, lay outside the pomerium line and was in other words outside the religious city. It continued thus all through the republic and into the empire until the reign of Claudius. Originally the pomerium line played an important part in the religious world and it continued to do so until the middle of the republic, during the Second Punic War, when its sanctity was destroyed and it lost its real religious significance, though it remained as a formal institution. As a divine barrier it served originally in the world of the gods very much the same purpose as the material wall of stone did in the world of men. Before the problem of foreign gods had begun to exist for the Romans, in the good old days when they knew only the gods of their own religion, the pomerium served to keep within the bounds of Rome all the beneficent kindly gods whose presence was not needed outside in the fields, and it served fully as important a purpose in keeping outside of Rome the gods who were feared rather than loved, for example the dread war-god Mars. When foreign gods began to be introduced into Rome they might, of course, be worshipped inside the pomerium by private individuals, but when the state acknowledged them it was more prudent that her worship should be outside the sacred wall. Thus it came to pass that the foreign gods, who were taken into the cult of the Roman state, were given temples in the Campus Martius or over on the Aventine, and the two or three cases where they were publicly worshipped inside the pomerium form no real exception to this rule—such an exception would be, in fact, quite unthinkable in the strictly logical system of Roman worship—but these gods were allowed inside because they came to Rome from her kinsfolk, the Latins, and were not felt to be foreign.
Hercules is one of the cases in this last category. Though originally, as we have seen, a Greek god, his long residence in Tibur (Tivoli) had made him, as it were, a naturalised citizen of Latium, and hence Rome felt it no impropriety to take him inside her pomerium. At first his worship seems to have been carried on by two clans, the Potitii and the Pinarii, but later, during the republic, the state assumed control. But though it was really the Greek Herakles who had come in as the latinised Hercules, the god had paid a certain price for his admission, for he came stripped of all the various attributes which he had had in Greece and retaining merely his function as patron of trade and travel. It was this practical side of his nature alone which appealed to the Romans; it found its expression in the offering of "the tenth" at the great altar in the Forum Boarium. This altar always remained in a certain sense the centre of Hercules-worship in Rome. It was reinforced at an early date by no less than three temples of Hercules in the more or less immediate neighbourhood, all of which were characterised by the same relative simplicity of ritual. Centuries later Herakles became known to the Romans through direct Greek channels, and it was recognised that this new Herakles was akin to the old Hercules, so that he too was called Hercules. There was nothing surprising in this to the Romans, because they considered it a matter of course that there should be found a parallel among their own gods for each Greek deity. They never understood the true state of affairs; it is doubtful whether they could have understood it: namely, that in almost all their other identifications of Roman and Greek deities, they were really doing violence to their own native gods by superimposing upon them the attributes of a deity with whom they had really nothing in common, whereas, in identifying the new Herakles with their old Hercules, they were doing a perfectly legitimate thing. For one who knows the true state of affairs there is something pathetically amusing in the fact that they really showed more delicacy in making their old (really originally Greek) Hercules into the new Greek Herakles-Hercules, than they did in throwing together Neptune and Poseidon, Mars and Ares, Diana and Artemis. As a matter of fact they always reverenced the old cult of the great altar, and never allowed the more sensational phases of Greek worship to be practised there, and put off into another quarter the temples which were built to Hercules under the various new attributes which the new Greek cult brought with it. These temples were placed, as was proper, outside the pomerium, in the southern part of the Campus Martius.
But to return to the simple Hercules and the Servian regime, the Roman state had now obtained a deity, of which, by the contagion of commerce, they already felt a need, a god of great power from whom came success in the practical undertakings of life. Hence he had a strong hold on the Romans whose practical side was undergoing a rapid development. The idea of trade was now represented in the religious world, it had received its divine sanction.
The other god, who came up from Magna Graecia and whose formal acceptance into the state-cult formed one of the earliest incidents in the breakdown of the old agricultural religion, was Castor, with his twin-brother Pollux, although brother Pollux was always an insignificant partner, so much so that the temple which was subsequently built to them both was referred to either as the temple of "Castor" alone or as the temple of "the Castors." At various points in the old Greek world we meet with a pair of brothers, at first not designated by individual names but merely named as a pair. Even these pair-names do not agree, but they represent all of them the same idea. Later when individual names are substituted for the general pair-name, these individual names also differ. They are gods of protection, and on the sea-coast—and most of Greece is sea-coast—they are especially helpful as rescuers from the dangers of the sea, and they are also very early and almost everywhere connected with horses. But in spite of their usefulness they are not very prominent, and it is doubtful whether they would ever have become famous, except for one of those little accidents which make the fortunes of gods as well as of men. It so happened that horses began to be used in warfare more than for the mere drawing of chariots; a primitive sort of cavalry came into being, produced by mounting heavy-armed foot-soldiers on horseback. With this cavalry the "Twin-Brothers" (Dios-kouroi = "Sons of Zeus"), especially Castor, became prominent. Just as the Greek merchants had taken Herakles with them when they set out to plant colonies in Southern Italy, so the heavy-mounted horsemen carried their god Castor with them wherever they went. The Italic tribes in their turn were quick to seize upon this idea of cavalry, and with it as an essential part went its divine patron, Castor. Thus the Castor-cult moved steadily northward, carried, as it were, on horseback. At last it reached Latium, and there the little town of Tusculum, afterwards so famous as the residence of Cicero, became in some unaccountable way an important cult-centre, and did for Castor what Tibur had done for Hercules, i.e. latinised him, so that Rome received him not as an alien but as one of her kin. There can be little doubt that the Roman cult actually did come from Tusculum, and that in its introduction into Rome, as in every other step on its march, it was connected with the reorganisation of the cavalry. This would seem to imply that Tusculum was famous for its cavalry and that Rome took the idea of it from her—statements for which we have unfortunately no other confirmation, though we have abundant proof of the cult at Tusculum and of Rome's close association with it.
Castor was thus the patron of the "horsemen" (equites) and his great day was July 15, when the horsemen's parade took place. Possibly this had been the date of the festival at Tusculum, a day especially appropriate because it was the Ides of the month, and the Ides were sacred to Juppiter, whose sons Castor and Pollux (Dios-kouroi) were supposed to be. It is extremely interesting in the light of this knowledge of the true state of affairs to see how legend later explained the coming of Castor and Pollux. It was an incident in the mythical war which was supposed to have taken place after the last Tarquin had been driven out, and the republic had been started. The adversaries of Rome, allied with Tarquin, notably Octavius Mamilius of Tusculum, fought against the Romans in the battle of Lake Regillus on July 15, B.C. 499. The Romans won, and the first news of victory was brought to Rome by the miraculous appearance of Castor and Pollux who were seen watering their horses in the Forum at the spring of Juturna. A temple on this spot was then vowed and fifteen years later, B.C. 484, it was completed and dedicated. Tusculum, July 15, and the dedication of the temple in B.C. 484 are seemingly the only historical facts in this legend; and long before B.C. 499 Castor was worshipped in Rome, especially on July 15. The site of his original worship was without doubt the same locality in the Forum where his temple was subsequently built, for it is an almost invariable rule that the earliest temples are built on the actual site of, or close to, the old altar or shrine which preceded the formal temple. Like Hercules therefore he was received inside the pomerium, and probably for a similar reason, because it was felt that he was a god of Tusculum, and hence a god of Rome's kinsfolk. We have an additional confirmation of this feeling in the way in which the later direct cult of Castor was treated. This cult, connecting Castor with healing and the interpretation of dreams, and emphasising his function as a rescuer from the dangers of the sea, would have been without meaning for the old Romans who worshipped him merely as a patron of horsemen and horsemanship. The new ideas seem to have had as their centre a later temple in the Circus Flaminius and thus Hercules and Castor may again be paralleled, since they have, each of them, an old cult-centre inside the pomerium, Hercules in the Forum Boarium, Castor in the Forum, and a later cult-centre, for more advanced ideas, in each case in the Circus Flaminius.
Although it was Greek influence which ultimately caused the destruction of Roman religion, and although the cults of Hercules and of Castor are the first definite effects of this influence, it cannot be said that the destruction had in any sense begun, because in their slow journey northward, and in their long residence at Tibur and Tusculum respectively, the two cults had lost all that was pernicious. The Roman instinct, which felt them to be akin to itself, did not go amiss; they were indeed akin to the new Rome with its new interest in trade and its increased interest in warfare, for the trader and the warrior have gone side by side in all ages of the world's history, whether it be a primitive instinct to grasp territory for commercial purposes or a more civilised endeavour to obtain an open port.