Jupiter is the god of the sky and thunder, and king of the gods in ancient Roman religion and mythology. Jupiter was the chief deity of Roman state religion throughout the Republican and Imperial eras, until Christianity became the dominant religion of the Empire. In Roman mythology, he negotiates with Numa Pompilius, the second king of Rome, to establish principles of Roman religion such as offering, or sacrifice.
Jupiter is usually thought to have originated as a sky god. His identifying implement is the thunderbolt and his primary sacred animal is the eagle, which held precedence over other birds in the taking of auspices and became one of the most common symbols of the Roman army (see Aquila). The two emblems were often combined to represent the god in the form of an eagle holding in its claws a thunderbolt, frequently seen on Greek and Roman coins. As the sky-god, he was a divine witness to oaths, the sacred trust on which justice and good government depend. Many of his functions were focused on the Capitoline Hill, where the citadel was located. In the Capitoline Triad, he was the central guardian of the state with Juno and Minerva. His sacred tree was the oak.
The Romans regarded Jupiter as the equivalent of the Greek Zeus, and in Latin literature and Roman art, the myths and iconography of Zeus are adapted under the name Jupiter. In the Greek-influenced tradition, Jupiter was the brother of and Pluto, the Roman equivalents of Poseidon and Hades respectively. Each presided over one of the three realms of the universe: sky, the waters, and the underworld. The Italic Diespiter was also a sky god who manifested himself in the daylight, usually identified with Jupiter. Tinia is usually regarded as his Etruscan counterpart.
The Romans believed that Jupiter granted them supremacy because they had honoured him more than any other people had. Jupiter was "the fount of the auspices upon which the relationship of the city with the gods rested." He personified the divine authority of Rome's highest offices, internal organization, and external relations. His image in the Republican and Imperial Capitol bore regalia associated with Rome's ancient kings and the highest consular and Imperial honours.
The consuls swore their oath of office in Jupiter's name, and honoured him on the annual feriae of the Capitol in September. To thank him for his help, and to secure his continued support, they sacrificed a white ox (bos mas) with gilded horns. A similar sacrificial offering was made by triumphal generals, who surrendered the tokens of their victory at the feet of Jupiter's statue in the Capitol. Some scholars have viewed the triumphator as embodying (or impersonating) Jupiter in the triumphal procession.
Jupiter's association with kingship and sovereignty was reinterpreted as Rome's form of government changed. Originally, Rome was ruled by kings; after the monarchy was abolished and the Republic established, religious prerogatives were transferred to the patres, the patrician ruling class. Nostalgia for the kingship (affectatio regni) was considered treasonous. Those suspected of harbouring monarchical ambitions were punished, regardless of their service to the state. In the 5th century BC, the triumphator Camillus was sent into exile after he drove a chariot with a team of four white horses (quadriga)—an honour reserved for Jupiter himself. When Marcus Manlius, whose defense of the Capitol against the invading Gauls had earned him the name Capitolinus, was accused of regal pretensions, he was executed as a traitor by being cast from the Tarpeian Rock. His house on the Capitoline Hill was razed, and it was decreed that no patrician should ever be allowed to live there. Capitoline Jupiter represented a continuity of royal power from the Regal period, and conferred power to the magistrates who paid their respects to him.
During the Conflict of the Orders, Rome's plebeians demanded the right to hold political and religious office. During their first secessio (similar to a general strike), they withdrew from the city and threatened to found their own. When they agreed to come back to Rome they vowed the hill where they had retreated to Jupiter as symbol and guarantor of the unity of the Roman res publica. Plebeians eventually became eligible for all the magistracies and most priesthoods, but the high priest of Jupiter (Flamen Dialis) remained the preserve of patricians.
Flamen and Flaminica Dialis
Jupiter was served by the patrician Flamen Dialis, the highest-ranking member of the flamines, a college of fifteen priests in the official public cult of Rome, each of whom was devoted to a particular deity. His wife, the Flaminica Dialis, had her own duties, and presided over the sacrifice of a ram to Jupiter on each of the nundinae, the "market" days of a calendar cycle, comparable to a week. The couple were required to marry by the exclusive patrician ritual confarreatio, which included a sacrifice of spelt bread to Jupiter Farreus (from far, "wheat, grain").
The office of Flamen Dialis was circumscribed by several unique ritual prohibitions, some of which shed light on the sovereign nature of the god himself. For instance, the flamen may remove his clothes or apex (his pointed hat) only when under a roof, in order to avoid showing himself naked to the sky—that is, "as if under the eyes of Jupiter" as god of the heavens. Every time the Flaminica saw a lightning bolt or heard a clap of thunder (Jupiter's distinctive instrument), she was prohibited from carrying on with her normal routine until she placated the god.
Some privileges of the flamen of Jupiter may reflect the regal nature of Jupiter: he had the use of the curule chair, and was the only priest (sacerdos) who was preceded by a lictor and had a seat in the senate. Other regulations concern his ritual purity and his separation from the military function; he was forbidden to ride a horse or see the army outside the sacred boundary of Rome (pomerium). Although he served the god who embodied the sanctity of the oath, it was not religiously permissible (fas) for the Dialis to swear an oath. He could not have contacts with anything dead or connected with death: corpses, funerals, funeral fires, raw meat. This set of restrictions reflects the fulness of life and absolute freedom that are features of Jupiter.
The augures publici, augurs were a college of sacerdotes who were in charge of all inaugurations and of the performing of ceremonies known as auguria. Their creation was traditionally ascribed to Romulus. They were considered the only official interpreters of Jupiter's will, thence they were essential to the very existence of the Roman State as Romans saw in Jupiter the only source of state authority.
The fetials were a college of 20 men devoted to the religious administration of international affairs of state. Their task was to preserve and apply the fetial law (ius fetiale), a complex set of procedures aimed at ensuring the protection of the gods in Rome's relations with foreign states. Iuppiter Lapis is the god under whose protection they act, and whom the chief fetial (pater patratus) invokes in the rite concluding a treaty. If a declaration of war ensues, the fetial calls upon Jupiter and Quirinus, the heavenly, earthly and chthonic gods as witnesses of any potential violation of the ius. He can then declare war within 33 days.
The action of the fetials falls under Jupiter's jurisdiction as the divine defender of good faith. Several emblems of the fetial office pertain to Jupiter. The silex was the stone used for the fetial sacrifice, housed in the Temple of Iuppiter Feretrius, as was their sceptre. Sacred herbs (sagmina), sometimes identified as vervain, had to be taken from the nearby citadel (arx) for their ritual use.