The Five Books Against Marcion by Tertullian
Chapter III. --Marcion Insinuated the Untrustworthiness of Certain Apostles Whom St. Paul Rebuked The Rebuke Shows that It Cannot Be Regarded as Derogating from Their Authority. The Apostolic Gospels Perfectly Authentic.
In the scheme of Marcion, on the contrary, the mystery of the Christian religion begins from the discipleship of Luke. Since, however, it was on its course previous to that point, it must have had its own authentic materials, by means of which it found its own way down to St. Luke; and by the assistance of the testimony which it bore, Luke himself becomes admissible. Well, but Marcion, finding the Epistle of Paul to the Galatians (wherein he rebukes even apostles ) for |not walking uprightly according to the truth of the gospel,| as well as accuses certain false apostles of perverting the gospel of Christ), labours very hard to destroy the character of those Gospels which are published as genuine and under the name of apostles, in order, forsooth, to secure for his own Gospel the credit which he takes away from them. But then, even if he censures Peter and John and James, who were thought to be pillars, it is for a manifest reason. They seemed to be changing their company from respect of persons. And yet as Paul himself |became all things to all men,| that he might gain all, it was possible that Peter also might have betaken himself to the same plan of practising somewhat different from what he taught. And, in like manner, if false apostles also crept in, their character too showed itself in their insisting upon circumcision and the Jewish ceremonies. So that it was not on account of their preaching, but of their conversation, that they were marked by St. Paul, who would with equal impartiality have marked them with censure, if they had erred at all with respect to God the Creator or His Christ. Each several case will therefore have to be distinguished. When Marcion complains that apostles are suspected (for their prevarication and dissimulation) of having even depraved the gospel, he thereby accuses Christ, by accusing those whom Christ chose. If, then, the apostles, who are censured simply for inconsistency of walk, composed the Gospel in a pure form, but false apostles interpolated their true record; and if our own copies have been made from these, where will that genuine text of the apostle's writings be found which has not suffered adulteration? Which was it that enlightened Paul, and through him Luke? It is either completely blotted out, as if by some deluge -- being obliterated by the inundation of falsifiers -- in which case even Marcion does not possess the true Gospel; or else, is that very edition which Marcion alone possesses the true one, that is, of the apostles? How, then, does that agree with ours, which is said not to be (the work) of apostles, but of Luke? Or else, again, if that which Marcion uses is not to be attributed to Luke simply because it does agree with ours (which, of course, is, also adulterated in its title), then it is the work of apostles. Our Gospel, therefore, which is in agreement with it, is equally the work of apostles, but also adulterated in its title.