The story telling how these books came into the possession of the Roman State through a woman who sold them to Tarquin—according to one version Tarquin the Elder, according to another Tarquin the Younger—is found in Roman authors who were well known and read throughout the whole middle age. The woman was a Sibylla, according to Varro the Erythreian, so called from a Greek city in Asia Minor; according to Virgil the Cumæan, a prophetess from Cumæ in southern Italy. Both versions could easily be harmonised, for Cumæ was a Greek colony from Asia Minor; and we read in Servius' commentaries on Virgil's poems that the Erythreian Sibylla was by many regarded as identical with the Cumæan. From Asia Minor she was supposed to have come to Cumæ.

In western Europe the people of the middle age claimed that there were twelve Sibyllas: the Persian, the Libyan, the Delphian, the Cimmerinean, the Erythreian, the Samian, the Cumæan, the Hellespontian or Trojan, the Phrygian and Tiburtinian, and also the Sibylla Europa and the Sibylla Agrippa. Authorities for the first ten of these were the Church father Lactantius and the West Gothic historian Isodorus of Sevilla. The last two, Europa and Agrippa, were simply added in order to make the number of Sibyllas equal to that of the prophets and the apostles.

But the scholars of the middle ages also knew from Servius that the Cumæan Sibylla was, in fact, the same as the Erythreian; and from the Church father Lactantius, who was extensively read in the middle ages, they also learned that the Erythreian was identical with the Trojan. Thanks to Lactantius, they also thought they could determine precisely where the Trojan Sibylla was born. Her birthplace was the town Marpessus, near the Trojan Mount Ida. From the same Church father they learned that the real contents of the Sibylline books had consisted of narrations concerning Trojan events, of lives of the Trojan kings, &c., and also of prophecies concerning the fall of Troy and other coming events, and that the poet Homer in his works was a mere plagiator, who had found a copy of the books of the Sibylla, had recast and falsified it, and published it in his own name in the form of heroic poems concerning Troy.

This seemed to establish the fact that those books, which the woman from Cumæ had sold to the Roman king Tarquin, were written by a Sibylla who was born in the Trojan country, and that the books which Trojan bought off her contained accounts and prophecies—accounts especially in regard to the Trojan chiefs and heroes afterwards glorified in Homer's poems. As the Romans came from Troy, these chiefs and heroes were their ancestors, and in this capacity they were entitled to the worship which the Romans considered due to the souls of their forefathers. From a Christian standpoint this was of course idolatry; and as the Sibyllas were believed to have made predictions even in regard to Christ, it might seem improper for them to promote in this manner the cause of idolatry. But Lactantius gave a satisfactory explanation of this matter. The Sibylla, he said, had certainly prophesied truthfully in regard to Christ; but this she did by divine compulsion and in moments of divine inspiration. By birth and in her sympathies she was a heathen, and when under the spell of her genuine inspirations, she proclaimed heathen and idolatrous doctrines.

In our critical century all this may seem like mere fancies. But careful examinations have shown that an historical kernel is not wanting in these representations. And the historical fact which lies back of all this is that the Sibylline books which were preserved in Rome actually were written in Asia Minor in the ancient Trojan territory; or, in other words, that the oldest known collection of so-called Sibylline oracles was made in Marpessus, near the Trojan mountain Ida, in the time of Solon. From Marpessus the collection came to the neighbouring city Gergis, and was preserved in the Apollo temple there; from Gergis it came to Cumæ, and from Cumæ to Rome in the time of the kings. How it came there is not known. The story about the Cumæan woman and Tarquin is an invention, and occurs in various forms. It is also demonstrably an invention that the Sibylline books in Rome contained accounts of the heroes in the Trojan war. On the other hand, it is absolutely certain that they referred to gods and to a worship which in the main were unknown to the Romans before the Sibylline books were introduced there, and that to these books must chiefly be attributed the remarkable change which took place in Roman mythology during the republican centuries. The Roman mythology, which from the beginning had but few gods of clear identity with the Greek, was especially during this epoch enlarged, and received gods and goddesses who were worshipped in Greece and in the Greek and Hellenised part of Asia Minor where the Sibylline books originated. The way this happened was that whenever the Romans in trouble or distress consulted the Sibylline books they received the answer that this or that Greek-Asiatic god or goddess was angry and must be propitiated. In connection with the propitiation ceremonies the god or goddess was received in the Roman pantheon, and sooner or later a temple was built to him; and thus it did not take long before the Romans appropriated the myths that were current in Greece concerning these borrowed divinities. This explains why the Roman mythology, which in its oldest sources is so original and so unlike the Greek, in the golden period of Roman literature comes to us in an almost wholly Greek attire; this explains why Roman and Greek mythology at that time might be regarded as almost identical. Nevertheless the Romans were able even in the later period of antiquity to discriminate between their native gods and those introduced by the Sibylline books. The former were worshipped according to a Roman ritual, the latter according to a Greek. To the latter belonged Apollo, Artemis, Latona, Ceres, Hermes, Mercury, Proserpina, Cybile, Venus, and Esculapius; and that the Sibylline books were a Greek-Trojan work, whose original home was Asia Minor and the Trojan territory, was well known to the Romans. When the temple of the Capitoline Jupiter was burned down eighty-four years before Christ, the Sibylline books were lost. But the State could not spare them. A new collection had to be made, and this was mainly done by gathering the oracles which could be found one by one in those places which the Trojan or Erythreian Sibylla had visited, that is to say, in Asia Minor, especially in Erythræ, and in Ilium, the ancient Troy.

So far as Hermes-Mercury is concerned, the Roman annals inform us that he got his first lectisternium in the year 399 before Christ by order from the Sibylline books. Lectisternium was a sacrifice: the image of the god was laid on a bed with a pillow under the left arm, and beside the image was placed a table and a meal, which as a sacrifice was offered to the god. About one hundreds years before that time, Hermes-Mercury had received his first temple in Rome.

Hermes-Mercury seemed, therefore, like Apollo, Venus, Esculapius, and others, to have been a god originally unknown to the Romans, the worship of whom the Trojan Sibylla had recommended to the Romans.

This was known to the scholars of the middle age. Now, we must bear in mind that it was as certain to them as an undoubted scientific fact that the gods were originally men, chiefs, and heroes, and that the deified chief whom the Romans worshipped as Mercury, and the Greeks as Hermes, was the same as the Teutons called Odin, and from whom distinguished Teutonic families traced their descent. We must also remember that the Sibylla who was supposed to have recommended the Romans to worship the old king Odin-Mercurius was believed to have been a Trojan woman, and that her books were thought to have contained stories about Troy's heroes, in addition to various prophecies, and so this manner of reasoning led to the conclusion that the gods who were introduced in Rome through the Sibylline books were celebrated Trojans who had lived and fought at a time preceding the fall of Troy. Another inevitable and logical conclusion was that Odin had been a Trojan chief, and when he appears in Teutonic mythology as the chief of gods, it seemed most probable that he was identical with the Trojan king Priam, and that Priam was identical with Hermes-Mercury.

Now, as the ancestors of the Romans were supposed to have emigrated from Troy to Italy under the leadership of Æneas, it was necessary to assume that the Romans were not the only Trojan emigrants, for, since the Teutons worshipped Odin-Priamus-Hermes as their chief god, and since a number of Teutonic families traced their descent from this Odin, the Teutons, too, must have emigrated from Troy. But, inasmuch as the Teutonic dialects differed greatly from the Roman language, the Trojan Romans and the Trojan Teutons must have been separated a very long time.

They must have parted company immediately after the fall of Troy and gone in different directions, and as the Romans had taken a southern course on their way to Europe, the Teutons must have taken a northern. It was also apparent to the scholars that the Romans had landed in Europe many centuries earlier than the Teutons, for Rome had been founded already in 754 or 753 before Christ, but of the Teutons not a word is to be found in the annals before the period immediately preceding the birth of Christ. Consequently, the Teutons must have made a halt somewhere on their journey to the North. This halt must have been of several centuries' duration, and, of course, like the Romans, they must have founded a city, and from it ruled a territory in commemoration of their fallen city Troy. In that age very little was known of Asia, where this Teutonic-Trojan colony was supposed to have been situated, but, both from Orosius and, later, from Gregorius of Tours, it was known that our world is divided into three large divisions—Asia, Europe, and Africa—and that Asia and Europe are divided by a river called Tanais. And having learned from Gregorius of Tours that the Teutonic Franks were said to have lived in Pannonia in ancient times, and having likewise learned that the Mœotian marshes lie east of Pannonia, and that the Tanais empties into these marshes, they had the course marked out by which the Teutons had come to Europe—that is, by way of Tanais and the Mœotian marshes. Not knowing anything at all of importance in regard to Asia beyond Tanais, it was natural that they should locate the colony of the Teutonic Trojans on the banks of this river.