In the earliest period of Roman state religion, Jupiter, Mars, and Quirinus were the supreme triad. The Romans, however, tolerant of new gods and religions (provided that no harm was done to the state as such), adopted many foreign gods. Under the influence of the Etruscans and other Italic communities, new gods began to appear about the 7th cent. B.C. A wider and much more significant influence, however, was that of the Greek and Middle Eastern cults from about the 3d cent. B.C. Old Roman deities were equated with the Greek gods and accordingly endowed with their attributes and myths. Such important cults as the worship of Dionysus and Apollo were brought to Rome. Greek philosophy, particularly that of the Epicureans (see Epicurus) and the Stoics (see Stoicism), began to influence Roman religious thought.
In the last two centuries of the republic—when the old basis of Roman religion had lost much of its importance, and when the state had grown so massive and distant that its ceremonies failed to satisfy the populace—religious feeling rapidly degenerated. The people, needing a new and emotionally more satisfying religion, turned toward the religious mysteries and the Middle Eastern cults. The most prominent were those of the Great Mother (see Cybele), Isis and Osiris, Sol, and Mithra. Old Roman worship had been controlled, impersonal, and concerned with matters of the everyday world. The new cults, which centered around the individual, promised personal salvation and blessed afterlife. It was in this religious air that Christianity took root and eventually triumphed.