I desire to hear from Marcion the origin of Paul the apostle. I am a sort of new disciple, having had instruction from no other teacher. For the moment my only belief is that nothing ought to be believed without good reason, and that is believed without good reason which is believed without knowledge of its origin: and I must with the best of reasons approach this inquiry with uneasiness when I find one affirmed to be an apostle, of whom in the list of the apostles in the gospel I find no trace. So when I am told that he [i.e., Paul] was subsequently promoted by our Lord, by now at rest in heaven, I find some lack of foresight in the fact that Christ did not know beforehand that he would have need of him, but after setting in order the office of apostleship and sending them out upon their duties, considered it necessary, on an impulse and not by deliberation, to add another, by compulsion so to speak and not by design [i.e., on the Road to Damascus]. So then, shipmaster out of Pontus [i.e., Marcion], supposing you have never accepted into your craft any smuggled or illicit merchandise, have never appropriated or adulterated any cargo, and in the things of God are even more careful and trustworthy, will you please tell us under what bill of lading you accepted Paul as apostle, who had stamped him with that mark of distinction, who commended him to you, and who put him in your charge? Only so may you with confidence disembark him [i.e., Paul]: only so can he avoid being proved to belong to him who has put in evidence all the documents that attest his apostleship. He [i.e., Paul] himself, says Marcion, claims to be an apostle, and that not from men nor through any man, but through Jesus Christ. Clearly any man can make claims for himself: but his claim is confirmed by another person’s attestation. One person writes the document, another signs it, a third attests the signature, and a fourth enters it in the records. No man is for himself both claimant and witness. Besides this, you have found it written that many will come and say, I am Christ. If there is one that makes a false claim to be Christ, much more can there be one who professes that he is an apostle of Christ.... [L]et the apostle, belong to your other god...."Against Marcion," cir. 212AD
Tertullian - Early Church Apologist. My how the church changed their mind!