In a superb article in a 1963 issue of Past & Present , GEM de Ste. Croix asks why Christians were persecuted. He finds the answer in Christian exclusiveness, their refusal to pay homage to the gods, which endangered the pax deorum on which the empire depended. Both common pagans and emperors set about persecution for religious reasons.
Along the way, he gives some brilliant insight into the workings of Roman criminal law, or, more precisely, the absence of such. In contrast to private law, Roman criminal law was virtually non-existent, and left a great deal to the discretion of officials. What, he asks, “was the legal foundation for the charges against Christians?” and answers that there was none:
“no foundation was necessary, other than a prosecutor, a charge of Christianity, and a governor willing to punish on that charge. Theories that the Christian churches could be legally regarded as collegia illicita , unlawful associations, either in the sense of being irremediably illegal (so that their members were at all times liable to criminal punishment), or merely because they were unlicensed (and liable to be prosecuted if they failed to obey an order to disband), have been strongly attacked in recent years by specialists in Roman public law; and in spite of some texts which suggest there may have been some technical irregularity, I am convinced that this issue can have had no real importance: we never hear that any Christian was ever prosecuted as a member of a collegium illicitum .”
Persecution of Christians aimed not at conviction, which made martyrs, but at apostasy. Tertullian spotted the inequity: “Others, who plead gulty, you torture to make them confess, the Christians alone to make them deny. de Ste. Croix sees here “a lonely anomaly in the Roman legal system. The explanation is that the only punishable offence was being a Christian, up to the very moment sentence was pronounced, not having been one. I certainly know of no parallel to this in Roman criminal law.”
If the persecutions reveal the arbitrary underside of Roman criminal procedures, they also reveal that the justice system was populated by feeble Pilates: “The governor was advised by a first-century jurist to consider not so much what was the practice at Rome as what the circumstances required; and the principle that in the exercise of his criminal jurisdiction the governor should act according to the circumstances existing in his particular province was well recognized. Probably the main reason why some martyrdoms -perhaps many martyrdoms – took place was that they were thought to be necessary if the province were to be kept ’ pacata atque quieta .’”