Jupiter, the chief god of the Romans. Etymologically identical with the Sanskrit Dyau, the Greek Zeus, and the Teutonic Tiu or Zio, Jupiter is one of the few gods that can safely claim to be descended from the Indo-European primeval period, and consequently one of the few exceptions to the rule that, if a deity is common to the Greeks and the Romans, he was borrowed by the latter from the former in historical times. But though Jupiter was known to the Italians from the time when they first became a separate branch of the Indo-European people, it would be an error to imagine that everything that can be predicated of the Greek Zeus holds good of the Roman god, or that the attributes of Jupiter can be ascribed indiscriminately to the Greek deity. We do indeed find that the same tales are told about Jupiter by Virgil and Ovid as had been related about Zeus by the Greek poets whom the Roman writers imitated; but it by no means follows that these tales were known to the Italians before their contact in historical times with the Greeks. On the contrary, it is in some cases perfectly certain that the myths were borrowed by the Romans from the Greeks. For instance, no myth in which Apollo figures along with Jupiter could possibly be an original Italian production, because it was only in historical times that the worship of Apollo was introduced from Greece into Italy. In this article, therefore, we must refer the reader for all that regards the Greek god to the article ZEUS. But, although we propose here to confine ourselves to the Roman deity, it is by no means easy to determine the outlines of this figure in mythology as it appeared to the religious consciousness of the Italians before they came in contact with Greek thought. We have but little direct information as to the Italians of that period. A few of the indigitamenta or formulæ containing the epithets of the gods which were recited as a sort of litany by the Roman priests have survived to us, but not enough for our purpose. We are therefore reduced to general considerations. And from this point of view there is no reason whatever for assuming that the resemblance between Jupiter and the Greek Zeus was originally any greater than that between Jupiter and the Sanskrit Dyau or the Gothic Tiu. As long as it was an accepted theory that the ancestors of the Greeks and Romans dwelt together, and apart from the rest of the Indo-European family, for some time before immigrating into their respective historical abodes, the case was different.
Now, however, this Pelasgian theory no longer has the sanction of either philology or archaeology. We must, therefore, conceive the difference between the original Italian Jupiter and the Greek Zeus to have been determined by the general differences between Greek and Roman religion. In the striking words of Mommsen (History of Rome, i. 28), 'As the Greek, when he sacrificed, raised his eyes to heaven, so the Roman veiled his head; for the prayer of the former was vision, that of the latter reflection.' The Greek gods were thoroughly anthropomorphic; they were represented by their poets and their sculptors alike in the image of man. The gods of the Romans were much nearer the earlier stage of animism; they were powers whose good-favour could be propitiated and ill-will averted by the proper ritual and by sacrifice, but they were not subjects for plastic art until the time of Greek influence. This difference will at once account for the fact that no myths whatever attach to the Italian Jupiter—all that are related of him were borrowed in late times from the Greek Zeus. What we do find is that various epithets, such as Lucetius and Elicius, Imbricator, Prodigialis, Depulsor, &c., are applied to him. And we may conjecture that all such epithets were probably, as some certainly were, originally part of the indigitamenta, with the recital of which the Roman priests sought to secure the favour of the god. In the next place it is to be noted that these epithets tend to show that Jupiter was originally to the Roman just as abstract a figure as Janus ('the spirit of opening'), Juventus ('the spirit of youth'), or Forculus ('the spirit of doors'), Limentinus ('the spirit of thresholds'), or Cardea ('the spirit of door-hinges'). And we may conjecture that the Romans, who have retained the original Indo-European word for priest (flamen = Sansk. brahman) which the Greeks lost, also present to us the original animism of the Indo-Europeans more faithfully than does the anthropomorphism of the Greeks. That Jupiter was to the Italians, as to the Indo-Europeans, the spirit of the sky, is shown by his epithet Lucetius, which occurred in the Saliaric Hymns. The same conception is at the bottom of the epithets which designate Jupiter as the spirit of thunder or of lightning—Jupiter Tonans, or Fulgur. As Jupiter Latarius he presided over the Latin alliance. As the supreme spirit apparently he was besought to grant victory in war, and hence the names Stator, Feretrius, Victor. The vintage also stood under the care of Jupiter Liber. The Ides of every month were sacred to him. He was also the spirit of oaths, Dius Fidius. Finally, although many of the epithets applied to him can at once be recognised as appropriate to the original character of Jupiter as spirit of the sky, such as Elicius, Fulminator, Pluvius, Imbricator, Serenator, Alnus, Frugiferus, there are others, such as Stator, Victor, &c., which cannot possibly be derived from his functions as a sky-spirit, and which must therefore be accretions, possibly resulting from the identification of the Roman Jupiter with the chief gods of the various allied states. The epithet Capitolinus is derived from the temple on the Capitol built by Tarquin, and the spirit inhabiting that temple was, compared with the rest, Jupiter Optimus, Maximus.