In an age of unbounded credulity the invitation to deceit was constant; and, while credulity itself means the faculty for innocent false witness, it could not be but that frauds were common in matters of miracle-working of all kinds. To suppose that all the miracle-stories arose in good faith when the deliberate manufacture of false documents and calculated tamperings with the genuine were a main part of the literary life of the Church, is to ignore all probability. The systematic forgery and interpolation of "Sibylline Books" by way of producing pagan testimonies and prophecies on the side of Christism, is to be regarded as a clerical industry of the second century. A bishop's business was to forward the fame and interests of his Church; and in Ambrose's transparent account of his discovery of miracle-working relics of saints at Milan in the fourth century we have a typical instance of the methods by which the prestige of the faith was advanced. Ambrose was above and not below the moral average of previous bishops. To find what might pass for the bones and relics of saints and martyrs, to frame false tales concerning them, to win illiterate and poor pagans to the Church by imitating their festivals and ceremonies--these were, by the grieving admission of many Christian historians, among the common activities of the Church from the second or third century onwards; and the priesthood were the natural agents of the work. By the very fact, however, that there were special reputations for wonder-working, as that of Gregory Thaumaturgus in the third century, we are reminded that the pretence was not universal. Imposture is a variation like another; and there must always have been a proportion of normally honest minds, however unintelligent and uncritical. It was their incapacity that evoked fraud. Some, on the other hand, have recorded how the bones of executed robbers were at times made to do duty as relics of martyrs.