Decline of Greco-Roman polytheism

Religion in the Greco-Roman world at the time of the Constantinian shift mostly comprised three main currents:

Early Christianity grew gradually in Rome and the Roman Empire from the 1st to 4th centuries, when it was legalized and, in its Nicene form became the state church of the Roman Empire with the Edict of Thessalonica of 380. Hellenistic polytheistic traditions survived in pockets of Greece throughout Late Antiquity. The Neoplatonic Academy was shut down by Justinian I in 529, a date sometimes taken to mark the end of Classical Antiquity.

The Romans tended towards syncretism, seeing the same gods under different names in different places of the Empire, accommodating other Europeans such as the Hellenes, Germans, and Celts, and Semitic and other groups in the Middle East. Under Roman authority, the various national myths most similar to Rome were adopted by analogue into the overall Roman mythos, further cementing Imperial control. Consequently, the Romans were generally tolerant and accommodating towards new deities and the religious experiences of other peoples who formed part of their wider Empire.

The more philosophical outlook of the Hellenic parts of the Roman empire led to a renaissance of intellectual religious thought around the start of the 2nd century. Writings pseudepigraphically attributed to Hermes Trismegistus, and discussing esoteric philosophy, magic, and alchemy, began to spread from Roman Egypt throughout the empire; while they are difficult to date with precision, these texts are likely to have been redacted between the first and third centuries. Although such hermetica was generally written with the theological aim of spiritual improvement, each text had an anonymous, eclectic, and spontaneous origin, rather than being part of an organised movement.

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