"How" a religion practiced was clearly also a factor, says Rüpke, who writes that Roman officials became suspicious of the worshippers of Dionysus and their practice of Bacchanalia because it "took place at night, but mainly because men and women celebrated together". , a scholar of Roman literature, says private divination, astrology, and 'Chaldean practices' (incantations to repulse demons) were also associated with 'night worship', and such magic carried the threat of banishment and execution in the early imperial period. Luke Lavan explains that private and secret religious rituals were associated with treason and secret plots against the emperor. Gathering at night (which Christians also did) smacked of conspiracy and political revolution. That required a police response. Bacchic associations were dissolved, leaders were arrested and executed, women were forbidden to hold important positions in the cult, no Roman citizen could be a priest, and strict control of the cult was thereafter established. Rüpke says the first occasion of such religious repression was in 186 BCE, and this treatment of the Bacchanals became the pattern for the Roman state's response to whatever it saw as a religious threat. In the first century of the common era, there were "periodic expulsions of astrologers, philosophers and even teachers of rhetoric... as well as Jews and...the cult of Isis". Druids also received the same treatment, as did Christians.