When did Irenæus, however, really write his work against Heresies? Although our sources of credible information regarding him are exceedingly limited, we are not without materials for forming a judgment on the point Irenæus was probably born about a.d. 140-145, and is generally supposed to have died at the beginning of the third century (a.d. 202).(1) We know that he was deputed by the Church of Lyons to bear to Eleutherus, then Bishop of Rome, the Epistle of that Christian community describing their sufferings during the persecution commenced against them in the seventeenth year of the reign of Marcus Aurelius Antoninus (7th March, 177--178).(2) It is very improbable that this journey was undertaken, in any case, before the spring of a.d. 178 at the earliest, and, indeed, in accordance with the given data, the {209} persecution itself may not have commenced earlier than the beginning of that year, so that his journey need not have been undertaken before the close of 178 or the spring of 179, to which epoch other circumstances might lead us.(1) There is reason to believe that he remained some time in Rome. Baronius states that Irenæus was not appointed Bishop of Lyons till a.d. 180, for he says that the see remained vacant for that period after the death of Pothinus in consequence of the persecution. Now certain expressions in his work show that Irenæus did not write it until he became Bishop.(2) It is not known how long Irenæus remained in Rome, but there is every probability that he must have made a somewhat protracted stay, for the purpose of making himself acquainted with the various tenets of Gnostic and other heretics then being actively taught, and the preface to the first Book refers to the pains he took. He wrote his work in Gaul, however, after his return from this visit to Rome. This is apparent from what he himself states in the Preface to the first Book: "I have thought it necessary," he says, "after having read the Memoirs [------] of the disciples of Valentinus as they call themselves, and _having had personal intercourse with some of them_ and acquired full knowledge of their opinions, to unfold to thee,"(3) &c. A little further on, he claims from the friend to whom he addresses his work indulgence for any defects of style on the score of his being resident amongst the Keltæ.(4) Irenæus no doubt during his stay in Rome came in {210}