Let us then, in attempting to do this, dismiss all secondary and precarious matter; such as (1) the argument drawn by Tischendorf [Endnote 254:1] from the order in which the names of the disciples of Valentinus are mentioned and from an impossible statement of Epiphanius which seems to make Heracleon older than Cerdon, and (2) the argument that we find in Volkmar and ’Supernatural Religion’ [Endnote 254:2] from the use of the present tense by Hippolytus, as if the two writers, Ptolemaeus and Heracleon, were contemporaries of his own in 225-235 A.D.  Hippolytus does indeed say, speaking of a division in the school of Valentinus, ’Those who are of Italy, of whom is Heracleon and Ptolemaeus, say’ &c.  But there is no reason why there should not be a kind of historic present, just as we might say, ’The Atomists, of whom are Leucippus and Democritus, hold’ &c., or ’St. Peter says this, St. Paul says that.’  The account of such presents would seem to be that the writer speaks as if quoting from a book that he has actually before him.  It is not impossible that Heracleon and Ptolemaeus may have been still living at the time when Hippolytus wrote, but this cannot be inferred simply from the tense of the verb.  Surer data are supplied by Irenaeus.

Irenaeus mentions Ptolemaeus several times in his first and second books, and on one occasion he couples with his the name of Heracleon.  But to what date does this evidence of Irenaeus refer?  At what time was Irenaeus himself writing.  We have seen that the terminus ad quem, at least for the first three books, is supplied by the death of Eleutherus (c.  A.D. 190).  On the other hand, the third book at least was written after the publication of the Greek version of the Old Testament by Theodotion, which Epiphanius tells us appeared in the reign of Commodus (180-190 A.D.).  A still more precise date is given to Theodotion’s work in the Paschal Chronicle, which places it under the Consuls Marcellus (Massuet would read ‘Marullus’) and Aelian in the year 184 A.D. [Endnote 255:1] This last statement is worth very little, and it is indeed disputed whether Theodotion’s version can have appeared so late as this.  At any rate we must assume that it was in the hands of Irenaeus about 185 A.D., and it will be not before this that the third book of the work ‘Against Heresies’ was written.  It will perhaps sufficiently satisfy all parties if we suppose that Irenaeus was engaged in writing his first three books between the years 182-188 A.D.  But the name of Ptolemaeus is mentioned very near the beginning of the Preface; so that Irenaeus would be committing to paper the statement of his acquaintance with Ptolemaeus as early as 182 A.D.

This is however the last link in the chain.  Let us trace it a little further backwards.  Irenaeus’ acquaintance with Ptolemaeus can hardly have been a fact of yesterday at the time when he wrote.  Ptolemaeus represented the ‘Italian’ branch of the Valentinian school, and therefore it seems a fair supposition that Irenaeus would come in contact with him during his visit to Rome in 178 A.D.; and the four years from that date to 182 A.D. can hardly be otherwise than a short period to allow for the necessary intimacy with his teaching to have been formed.