St. Irenaeus of Lyons, writing in the latter quarter of the second century, reckons him as the fifth pope in succession from the Apostles, though he says nothing of his martyrdom. His pontificate is variously dated by critics, e.g. 106-115 or 109-116. In Christian antiquity he was credited with a pontificate of about ten years, and there is no reason to doubt that he was on the...