acleon 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.