Augurs

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.

Fetials

The fetials were a college of 20 men devoted to the religious administration of international affairs of state.^[26] 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.^[27] 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.^[28]
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.^[29]

Jupiter and religion in the secessions of the plebs

The role of Jupiter in the conflict of the orders is a reflection of the religiosity of the Romans. Whereas the patricians were able to claim the support of the supreme god quite naturally being the holders of the auspices of the State, the plebs (also known as the plebeians) argued that as Jupiter was the source of justice he was on their side since their cause was just.
The first secession was caused by the excessive burden of debts that weighed on the plebs. Because of the legal institute of the nexum a debtor could become a slave of his creditor. The plebs argued the debts had become unsustainable because of the expenses of the wars wanted by the patricians. As the senate did not accede to the proposal of a total debt remission advanced by dictator and augur Manius Valerius Maximus the plebs retired on the Mount Sacer, a hill located three Roman miles to the North-northeast of Rome, past the Nomentan bridge on river Anio.^[30] The place is windy and was usually the site of rites of divination performed by haruspices. The senate in the end sent a delegation composed of ten members with full powers of making a deal with the plebs, of which were part Menenius Agrippa and Manius Valerius. It was Valerius, according to the inscription found at Arezzo in 1688 and written on the order of Augustus as well as other literary sources, that brought the plebs down from the Mount, after the secessionists had consecrated it to Jupiter Territor and built an altar (ara) on its summit. The fear of the wrath of Jupiter was an important element in the solution of the crisis. The consecration of the Mount probably referred to its summit only. The ritual requested the participation of both an augur (presumably Manius Valerius himself) and a pontifex.^[31]
The second secession was caused by the autocratic and arrogant behaviour of the decemviri who had been charged by the Roman people with writing down the laws in use till then kept secret by the patrician magistrates and the sacerdotes. All magistracies and the tribunes of the plebs had resigned in advance. The task resulted in the XII Tables, which though concerned only private law. The plebs once again retreated to the Sacer Mons: this act besides recalling the first secession was meant to seek the protection of the supreme god. The secession ended with the resignation of the decemviri and an amnesty for the rebellious soldiers who had deserted from their camp near Mount Algidus while warring against the Volscians, abandoning the commanders. The amnesty was granted by the senate and guaranteed by the pontifex maximus Quintus Furius (in Livy's version) (or Marcus Papirius) who also supervised the nomination of the new tribunes of the plebs, then gathered on the Aventine Hill. The role played by the pontifex maximus in a situation of vacation of powers is a significant element underlining the religious basis and character of the tribunicia potestas.^[32]