To undertake to set forth with any definiteness the "religious ideas of a Roman" of A.D. 64 would be an extremely difficult task. Those ideas would differ with the individual, being determined or varied by a number of considerations and influences - by locality, education, and temperament. Silius would not hold the views of Scius and probably not those of Marcia. We may speak of the "State religion" of Rome, as distinct from various other religions tolerated and practised in different parts of the empire, but it is scarcely possible to define the contents of that "State religion." There were certain special priests and priestly bodies who saw to it that certain rites and ceremonies should be perfortied scrupulously in a prescribed manner and on prescribed dates; but these were officers of the state, whose knowledge and functions were confined to the ritual observances with which they had to deal. They were not persons trained in a system of theology, nor were they preachers of a code of doctrines or morals; they had no "cure of souls," and belonged to no church; they had no credo and no Bible or corresponding authority to which to refer. Though most well-informed persons could have told the names of the prominent deities in the calendar - such as Jupiter, Mars, Apollo, and Ceres - perhaps scarcely any one but an encyclopaedist or antiquarian could have named one-half of the total. It is not merely that the deities on the list were so numerous. There were other reasons for ignorance or vagueness. In the first place, the line between the operations of one deity and those of another was often too fine to draw, and deities originally more or less distinct came to be confused or identified. Secondly, it was often hard, if not impossible, to make up one's mind whether a so-called deity - such as Virtue, Peace, or Health - was supposed to have a real existence, or whether it was simply the personification of an abstract quality. Thirdly, many of the ancient divinities had fallen out of fashion, and to a large extent out of memory, while many new ones - Isis and Serapis for example - had come, or were coming, into vogue.

The state possessed its old-established calendar of days sacred to a number of deities, and its code of ritual to be performed in their honour. There were ancient prescriptions as to what certain priests should wear, what they should do or avoid in their priestly character, what victims - ox, sheep, or pig - they should sacrifice, what instruments they should use for the purpose, and in what formula of words they should pray in particular connections. There was a standing commission, with the Pontifex Maximus - at this date that excellent religious authority, the emperor Nero - at its head, to safeguard the state religion, to see that its requirements were carried out, and that no one ventured to commit an outrage towards it. But the state could not have told you with any precision that you must believe in just so many deities and no others; it could not have told you precisely what notions to entertain concerning those deities whom it did officially recognise; it dictated no theological doctrines; neither did it dictate any moral doctrines beyond those which you would find in the secular law. It reserved the right to prevent the introduction of foreign or new divinities if it found sufficient cause; but so long as the temples, the rites and ceremonies, the cardinal moral axioms of the Roman "religion," and the basic principles of Roman society were respected, the state practised no sort of inquisition into your beliefs or non-beliefs, and in no way interfered with your particular selection of favourite deities.

Polytheism in an advanced community is always tolerant, because it is necessarily always indefinite. What it does not readily endure is an organised attack upon the entire system, whether openly avowed or manifestly implied. Even undisguised unbelief in any deity at all it is often willing to tolerate, so long as the unbelief is rather a matter of dialectics than anything else, and makes no attempt at a crusade. When a state so disposed is found to interfere with a novel religion, it will generally be easy to perceive that the jealousy is not on behalf of the deities nor of a creed, but on behalf of the community in its political, economic, or social aspect. This, however, is perhaps to anticipate. Let us endeavour to realise as best we can the religious situation among the Roman or romanized portion of the population.

Though we are not here directly concerned with the steps by which the Roman religion had come to be what it was, we can scarcely hope to understand the position without some comprehension of that development. The Romans were a conservative people, and many of the peculiarities of their worship were due to the retention of old forms which had lost such spirit as they once possessed.