The Only Witness for the Marcionite Canon Being Galatians First is Epiphanius and Epiphanius Isn't a Credibly Witness

I am very interested in the origins of Christianity.  When I meet someone new, I scour their personality for some sign that they are 'interesting.'  I find the exotic attractive.  For instance the consistent American mispronunciation of foreign words endlessly amusing to me.  Most truly don't have a clue that words like foyer (does not rhyme with voyeur), au gratin (does not sound like an Irish last name), en route (not 'in rout')  - are French!  From going to the Starbucks drive thru one too many times even I have started to call a small Italian biscuit, a 'bi-scotty.'  My wife has started to order 'brushetta' at the local restaurant and even develop a taste for Maggiano's (proper pronunciation not Ma-gee-a-no's).

If all these average people make little mistakes when it comes to foreign words, who's going to call out the professional scholars?  I am amazed when I read that 'Tertullian and Epiphanius' testify to the Marcionite canon having the Epistle to the Galatians first among the Pauline letters.  Really? Where exactly does Tertullian actually say that.  He doesn't.  It's another sloppy bit of misinformation that rarely gets called out. 

Certainly the ordering of Tertullian's attack against Marcion's interpretation of the Pauline canon is Galatians first.  But is this reflective of Marcion's canon, Tertullian's canon or his original source for Against Marcion (i.e. Irenaeus or some other source)?  The idea that Tertullian has a copy of Marcion's canon beside him and is 'reporting the facts' is a supposition.  It's not a proven fact.  Indeed if Tertullian was copying out an earlier source - something he does quite frequently (i.e. Against the Valentinians, Against Hermogenes, Against Marcion III/Against the Jews etc) the author's claim to be doing this would become transferred to Tertullian's hand.

The bottom line is that only Epiphanius claims that the Marcionite canon is Galatians first.  Tertullian's report treats Galatians first but plenty of 'orthodox' witnesses had Galatians first canons.  If Ephrem the Syrian wrote a commentary on the Pauline letters and it survived intact it would naturally begin Galatians first.  There were also Galatians first canons in Latin.  It would be quite natural for the dim witted Church Father Epiphanius to infer that the Marcionite canon was Galatians first based on a common source shared with Tertullian. 

Daniel Plooij gets it right when commenting on Epiphanius's claim that the Diatessaron was the Gospel to the Hebrews comes out and says what we've all thought at one time or another - “I think Epiphanius ought to be the last witness we should trust uncontrolled, especially in his testimonies on heretics and heretical writings. He combines all kinds of notices, rumours, and calumnies into abracadabra often completely incomprehensible." [A Primitive Text of the Diatessaron p. 78] Indeed Epiphanius's unreliability has been demonstrated in situations when he can be checked in his account of other heresies (e.g., F. L. Horton, The Melchixedek Tradition: a Critical Examination of the Sources to the 5th century A.D. [Cambridge, 1976], Chap. 4).

The claim that the Marcionite canon was Galatians first is solely based on the testimony of Epiphanius and therefore should not be taken seriously.