Mithras Slaying the Bull, a Relief from Aquileia
A tauroctony from Aquileia, second half of the second century AD, now in the Kunsthistorisches Museum in Vienna (inv. I 624). Mithras had no place in Rome's official calendar and no state priesthood, yet reliefs like this turn up in every province the army garrisoned.
Roman religious policy was not a single thing. The state maintained its own cults with public priesthoods and a fixed calendar; it licensed and absorbed foreign gods on terms it set; it occasionally expelled a cult and later readmitted it; and it left a great deal alone. Mithraism ran alongside all of that — private, initiatory, spread by soldiers and merchants rather than by decree, and never suppressed. Managing the gods of an empire meant deciding, case by case, which of those categories a new god belonged in. See how Rome managed the gods of an empire.
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