Jupiter, or Jove, was the supreme or high, god of the Roman pantheon, and recognized as father of the gods was closely identified with Zeus. His probable origin was an Etruscan god, for the Etruscan kings, with their own high god being called Tinia, instituted the cult of Jupiter Optimus Maximus, "best and greatest," but his name and characteristics more closely associate him to the Greeks. Being a sky-god, Jupiter Lucetius, he was the light-bringer, and days of the full moon. The Ides were sacred to him. Like Zeus, he was associated with rain and thunder, since his epithets include Tonans (thunder) and Fulgurator (sender of lightning), and his main sanctuary was located on Capitoline Hill, in Rome, contained the lapides silices, and believed to be his thunderbolts. Throughout Italy all of the sanctuaries honoring him were built on hills and places that had been struck by lightning. He was represented in the sanctuary of Jupiter Feretinus by a crude lump of stone.
Jupiter was not only the protective deity of the race, but he was regarded as the guardian of public morality, being concerned with oaths treaties, alliances, and wars. Socially Jupiter also was concerned with the citizen's duties toward the gods, state, and family. His annual dedication festival was observed on September 13, the day on which the consuls of the republic took office. He was particularly responsible for honoring oaths, which led to the practice of swearing in his name, by Jupiter! Or by Jove!
During his evolvement as a deity Jupiter was part of two trinities: the earlier trinity included Mars
and Quirinus. Later this trinity was revised to include Jupiter, Juno, and Minerva, all three whom shared the Capitoline Sanctuary.
Jupiter also played military roles as a war-god. As Jupiter Victor he lead legions to victory, and when the legions were on the defensive he was Jupiter Stator or Jupiter Protector. Away from Rome he was allied with the Syrian/Hittite god Dolichenus, and in this form became popular with the Roman military who erected shrines to him as far as Britain.
Increasing in honor Jupiter became the protector of all of the Roman people. With the development of urbanization and the increasing importance of the city, it was only natural that this tutelary deity should have risen to greater pre-eminence, while his associate Mars shed agricultural associations for more bellicose dispositions. Under the name of Jupiter Capitolinus, he presided over the Roman games, always an important feature of ancient city life. With the introduction of Emperor worship, a means of testing the loyalty of the subject as much as an official religion, Jupiter's political function was somewhat decreased, though traitors were still thrown from Tarpeian rock on Capitoline Hill. Jupiter was no longer the embodiment of the greatness and prosperity of the Roman Empire, but rather, he served as a divine guide of the world. Cicero, who in 43 BC had his head and hands cut off for advocating a return to republican principles, equated Jove with numen praestantissimae mentis, "the presence of a supreme mind." This was a conception not unlike monotheism of Christianity, to which the conversion of Emperor Constantine in 312 AD meant the beginning of the end of the European pagan era. A.G.H.
Cotterell, Arthur, A Dictionary of World Mythology, New York, G. P. Putman's Sons, 1980, pp. 145-146
Grimal, Pierre, Larousse World Mythology, Secaucus, New Jersey, Chartwell Books, 1965, p. 177
Jordan, Michael, Encyclopedia of Gods, New York, Facts On File, Inc. 1993, p. 125