That ius divinum was a part of the ius civile, the law of the Roman city-state; as the ius civile, exclusive of the ius divinum, regulated the relations of citizen to citizen, so did the ius divinum regulate the relations of the citizen to the deities of the community.

The priesthoods administering this law consisted not of sacrificing priests, attached to the cult of a particular god and temple, but of lay officials in charge of that part of the law of the State; it was no concern of theirs (so indeed they might quite well argue) whether the gods really existed or not, provided the law were maintained.

When in 61 B.C.Clodius was caught in disguise at the women's festival of the Bona Dea, the pontifices declared the act to be _nefas_,--crime against the ius divinum; but we may doubt whether any of those pontifices really believed in the existence of such a deity.

The idea of the _mos maiorum_ was still so strong in the mind of every true Roman, his conservative instincts were so powerful, that long after all real life had left the divine inhabitants of his city, so that they survived only as the dead stalks of plants that had once been green and flourishing, he was quite capable of being horrified at any open contempt of them.

And he was right, as Augustus afterwards saw clearly; for the masses, who had no share in the education described in the sixth chapter, who knew nothing of Greek literature or philosophy, and were full of superstitious fancies, were already losing confidence in the authorities set over them, and in their power to secure the good-will of the gods and their favour in matters of material well-being.
This is the only way in which we can satisfactorily account for the systematic efforts of Augustus to renovate the old religious rites and priesthoods, and we can fairly argue back from it to the tendencies of the generation immediately before him.