국교
In the wake of the Republic's collapse, State religion had adapted to support the new regime of the Emperors. Augustus, the first Roman emperor, justified the novelty of one-man rule with a vast program of religious revivalism and reform. Public vows formerly made for the security of the Republic now were directed at the wellbeing of the Emperor. So-called "Emperor worship" expanded on a grand scale the traditional Roman veneration of the ancestral dead and of the "Genius", the divine tutelary of every individual. Imperial cult became one of the major ways Rome advertised its presence in the provinces and cultivated shared cultural identity and loyalty throughout the Empire: rejection of the State religion was tantamount to treason. This was the context for Rome's conflict with Christianity, which Romans variously regarded as a form of atheism and threat to the stability of the Empire, causing the prosecution of anti-Christian policies; under Emperor Trajan's reign (AD 98–117), Roman intellectuals and functionaries (Lucian of Samosata, Tacitus, Suetonius, Pliny the Younger, and Celsus) gained knowledge about the Jewish roots of Early Christians, therefore many of them considered Christianity to be some sort of "superstitio Iudaica".