But Jupiter was there; and we know certain facts of his cult which give us a pretty clear idea of what the Romans of the pre-Etruscan period thought about him. In the calendar all Ides belonged to him, were _feriae Iovis_;[256] he seems to be the source of light, whether of sun or moon, for neither of which the Romans had any special divinity; in the hymn of the Salii he is addressed as Lucetius, the giver or source of light. The festivals of the vintage belonged to him, since the production of wine specially needed the aid of sun and light, and his flamen was employed in the cult on these occasions.[257] When rain was sorely needed, the aid of the sky-god was sought under the cult-title Elicius, and as Fulgur or Summanus[258] he was the Power who sent the lightning by day and by night. The ideas thus reflected in the Roman cult were common to all Italian peoples of the same stock; everywhere we find him worshipped on the summits of hills, and in woods of oak, ilex, or beech,[259] where nothing but the trees he loved intervened between the heaven and the earth.
His oldest cult at Rome was on the Capitoline hill, but at all times quite distinct from that which became so famous afterwards; he was known here as Feretrius, a cult-title of which the meaning is uncertain,[260] and here, so far as we can guess, there must have been an ancient oak regarded either as the dwelling of the numen or as the numen himself, upon which Romulus is said to have hung the _spolia opima_ taken from the king of the Caeninenses;[261] here we may see the earliest trace of the triumphal procession that was to be. Doubtless an _ara_ was here from the first, and then followed a tiny temple, only fifteen feet wide as Dionysius describes it from personal knowledge in the time of Augustus,[262] who restored it. There was no image of the god, but in the temple was kept a _silex_, probably a stone celt believed to have been a thunderbolt;[263] this stone the Fetiales took with them on their official journeys, and used it in the oath, _per Iovem lapidem_, with which they ratified their treaties. As the Romans thought of Jupiter, not as a personal deity living in the sky like Zeus, but rather as the heaven itself, so they could think of him as immanent in this stone, _Iuppiter lapis_. And the use of the flint in treaty-making suggests another aspect of the god, which he retained in one way or another throughout Roman history; it is his sanction that is called in to the aid of moral and legal obligations, resulting from treaties, oaths, and contracts such as that of marriage. As Dius Fidius he was invoked in the common Roman oath _medius fidius_; as Farreus (if this were an old cult-title) he gave his sanction to the solemn contract entered into in the ancient form of marriage by _confarreatio_, where his flamen had to be present, and where in all probability the cake of _far_ was eaten as a kind of sacrament by the parties to the covenant.[264] In much of this it is tempting to see, as we can see nowhere else in the Roman religion, faint traces of a feeling about the heaven-god brought from a remote pastoral life under the open sky, where neither forest nor mountain intervened to shelter man from the great Presence;[265] and it is also tempting to think that there was here, even for Latins who had learnt to worship Jupiter under the form of stocks and stones in the land of their final settlement, some chance of the development of a deity "making for righteousness."