The Romans were relatively tolerant during the early years of the empire. The governors of Roman provinces were concerned about tax and pax - about providing a steady stream of revenue for Rome and about maintaining tranquility within the province. The local religions could be tolerated or ignored as long as they didn’t interfere with these two goals.
Except for the uprisings of the Zealots, the Romans regarded Judaism as odd but harmless. Judaism was an outlier on the spectrum of religions because it was monotheistic and because it systematically wove ethics into its religious thought.
The other belief systems around the empire were polytheistic. They were less concerned with the ethics of good and evil, and more concerned with the pleasing or displeasing various deities. As historian Timothy Maschke writes:
During this same time period since the time of Augustus (63 BC - 14 AD, ruled 27 BC - 14 AD), Judaism had been recognized as a legitimate religion in the Roman Empire. While small numerically (estimates of 5-7% of the Roman populace), Judaism’s influence greatly exceeded its diminutive size. Judaism was an ancient religion with a revered tradition. Furthermore, it was the religion into which Jesus was born and from which the Christian church developed. This meant that more than a few of the beliefs and practices of Judaism carried over into Christianity, e.g., monotheism, Ten Commandments, and singing Psalms.
Later, Rome became less tolerant and began to persecute both Christians and Jews. Tellingly, the Romans at first made little distinction between the two groups.
The persecutions began because the Christians and Jews objected to the notion that the emperor was divine. Probably few Romans truly believed this formal declaration that the emperor was a god, but they were willing to publicly pronounce it as an official procedure.
Jews and Christians, on the other hand, were not willing to state the emperor’s divinity and thereby incurred Roman wrath.
Initially, the Romans rightly treated Christianity as a movement within Judaism, and punished Christians and Jews without distinguishing between the two. Later, Romans saw Christianity as a distinct group, especially as an increasing number of non-Jews became Christians.
Eventually, the number of gentile Christians being arrested, jailed, interrogated, tortured, and killed by the Romans far exceeded the number Jewish Christians, and by the end of the empire, Judaism and Christianity were seen as almost unrelated.
