JUPITER, in Latin IUPPITER, DIESPITER or lows, the chief Roman and Italian god ; like Zeus, with whom he is etymologically identical (root diu, "bright") he was a sky god. One of his most ancient epithets is Lucetius, the light-bringer ; and later literature has preserved the same idea in such phrases as sub love, under the open sky. All days of the full moon (ides) were sacred to him; as Jupiter Elicius he was propitiated with a peculiar ritual, to send rain in time of drought ; as Fulgur he had an altar in the Campus Martius, and all places struck by lightning were made his property and guarded from the profane by a circular wall. The vintage, which needs especially the light and heat of the sun, was under his particular care, and in the festivals (V inalia) con nected with it he was the deity invoked, and his flamen the priest employed.
Throughout Italy we find him worshipped on the summits of hills; thus on the Alban hill south of Rome was an ancient seat of his worship as Jupiter Latiaris, which was the centre of the league of 3o Latin cities of which Rome was originally an ordinary member. At Rome itself on the Capitoline hill we find his oldest temple, described by Livy (i. 1o) ; here we have a tradition of his sacred tree, the oak, common to the worship both of Zeus and Jupiter, and here, too, were kept the lapides silices, perhaps celts, believed to have been thunderbolts, which were used symbolically by the fetiales when officially declaring war or making treaties on behalf of the Roman state. Hence the curious form of oath, lovem lapidem iurare, used at Rome, both in public and private life. (See H. J. Rose, Roman Questions, p. 75; Primitive Culture in Italy, P. 45.) In Jupiter we undoubtedly see not only the great protecting deity of the race, but one, and perhaps the only one, whose wor ship embodies a distinct moral conception. He is specially con cerned with oaths, treaties and leagues, and it was in the presence of his priest that the most ancient and sacred form of marriage (confarreatio) took place. The lesser deities, Dius Fidius and Fides, were, perhaps, originally identical, certainly connected, with him. This connexion with the conscience, with the sense of obligation and right dealing, was never quite lost throughout Roman history. In Virgil's great poem, though Jupiter is in many ways as much Greek as Roman, he is still the great protecting deity who keeps the hero in the path of duty (pietas) towards gods, State and family.
But this aspect of Jupiter gained a new force and meaning at the close of the monarchy with the building of the famous temple on the Capitol, of which the foundations are still to be seen. It was dedicated to luppiter Optimus Maximus; i.e., the best and greatest of all the Jupiters, and with him were associated Juno and Minerva, in a fashion which clearly indicates a Graeco Etruscan origin ; for the combination of three deities in one temple was foreign to the ancient Roman religion, while it is found both in Greece and Etruria. Its dedication festival fell on Sept. 13, on which day the consuls originally succeeded to office, accompanied by the senate and other magistrates and priests, and, in fulfilment of a vow made by their predecessors, they offered to the great god a white ox, his favourite sacrifice, and after rendering thanks for the preservation of the State during the past year, made the same vow as that by which their predecessors had been bound. Then followed the epulum /ovis or feast of Jupiter, in which the three deities seem to have been visibly present in the form of their statues, Jupiter having a couch and each goddess a sella, and to have shared the meal with Senate and magistrates. In later times this day became the central point of the great Roman games (ludi Romani), origi nally games vowed in honour of the god if he brought a war to a successful issue. When a victorious army returned home the triumphal procession passed to this temple. (See TRIUMPH.) Throughout the Republic this remained the central Roman cult, and although Augustus's new foundations (Apollo Palatinus and Mars Ultor) were in some sense its rivals, that emperor was far too shrewd to attempt to oust luppiter Optimus Maximus from his paramount position ; he became the protecting deity of the reigning emperor as representing the State, as he had been the protecting deity of the free republic. His worship spread over the whole empire; a Capitol modelled on that of Rome was a feature of numerous important towns (e.g., Ostia), and the fact that the Romans chose the name of Jupiter, in almost every case, by which to indicate the chief deity of the subject peoples, proves that they continued to regard him, so long as his worship existed at all, as the god whom they them selves looked upon as greatest.
See ZEUS, ROMAN RELIGION, also G. Wissowa, Religion and Kultus, p. 113, et seq. ; articles "Iuppiter" in Roscher's Lexikon and Pauly Wissowa, Realencyklopadie, s.v.