" The old laissez-faire Roman ways, in which the worship of one god might simply be added to the worship of all the others, were, preachers told their congregations, no longer acceptable. Worship a different god, they explained, and you were not merely being different. You were demonic. Demons, said the clerics, dwelt in the minds of those who practised the old religions. Those who criticized Christianity, warned the Christian apologist Tertullian, were not speaking with a free mind. Instead, they were attacking the Christians because they were under the control of Satan and his footsoldiers. The ‘battleground’ of these fearsome troops was nothing other than ‘your minds, which have been attuned to him by his secret insinuations’. Demons were able to ‘take possession of men’s souls and block up their hearts’ and so stop them believing in Christ. "

― Catherine Nixey , The Darkening Age: The Christian Destruction of the Classical World