Although exceptional skill and learning have been devoted to the origins of martyr cult, undeniably this grand and highly distinguished tradition has been shaped by certain widely shared and long-standing assumptions. In particular, while great scholars such as Duchesne and Delehaye have exhibited a strong (and very proper) scepticism about particular legends, there has in general been a predisposition to accept at face value the underlying context as presented by the post-Constantinian Church. Most historians of the martyrs have followed hagiographical tradition and accepted that, as Pope Leo I claimed in the mid-fifth century, ‘uncounted numbers’ of the faithful had died in the imperial persecutions and were marked out as endowed with power ‘to help those in danger, to drive away sickness, to expel unclean spirits and to cure infirmities without number’. That carefully constructed picture, however, only emerges in the late fourth and fifth centuries, and it is the circumstances and processes which shaped its emergence that will be examined here.