I have already frequently mentioned the _ius divinum_, the law governing the relations between the divine and human inhabitants of the city, as the _ius civile_ governed the relations between citizen and citizen.[340] When we examined the calendar of Numa, we were in fact examining a part of this law; we began with this our studies of the religion of the Roman city-state, because it is the earliest document we possess which illuminates the dark ages of city life, so far as religion is concerned. The study of the calendar naturally led us on to consider the evidence it yields, taken together with other sources of information, as to the nature of the deities for whose worship it fixes times and seasons, or, more accurately, the amount of knowledge to which the Romans had attained about their divine beings. But we must now return to the _ius divinum_, and study it in another aspect, for which the calendar itself does not suffice as evidence. Perhaps the simplest way of explaining this _ius_ is to describe it as laying down the rules for the maintenance of right relations between the citizens and their deities; as ordaining what things are to be done or avoided in order to keep up a continual _pax_, or quasi-legal covenant, between these two parties. The two words _ius_ and _pax_, we may note, are continually meeting us in Roman religious documents. In a prayer sanctioned by the pontifices for use at the making of a new clearing, we read: "Si deus, si dea sit cuius illud sacrum est, _ut tibi ius siet_ porco piaculo facere illiusce sacri coercendi ergo,"[341] _i.e._ "O unknown deity, whether god or goddess, whose property this wood is, let it be legally proper to sacrifice to thee this pig as an expiatory offering, for the sake of cutting down trees in this wood of thine." "Pacem deorum exposcere" (or "petere") is a standing formula, as all readers of Virgil know;[342] and it occurs in many other authors and religious documents. When Livy wants to express the horror of the old patrician families at the idea of plebeians being consuls--men who had no knowledge of the _ius divinum_ and no right to have any--he makes Appius Claudius exclaim, "Nunc nos, tanquam iam nihil pace deorum opus sit, omnes caerimonias polluimus."[343] How can we maintain our right relations with the gods, if plebeians have the care of them?