Galatians 1:10-24,2:6

10For do I now persuade men, or God? or do I seek to please men? for if I yet pleased men, I should not be the servant of Christ. 11But I certify you, brethren, that the gospel which was preached of me is not after man. 12For I neither received it of man, neither was I taught it, but by the revelation of Jesus Christ. 13For ye have heard of my conversation in time past in the Jews’ religion, how that beyond measure I persecuted the church of God, and wasted it: 14And profited in the Jews’ religion above many my equals in mine own nation, being more exceedingly zealous of the traditions of my fathers. 15But when it pleased God, who separated me from my mother’s womb, and called me by his grace, 16To reveal his Son in me, that I might preach him among the heathen; immediately I conferred not with flesh and blood: 17Neither went I up to Jerusalem to them which were apostles before me; but I went into Arabia, and returned again unto Damascus. 18Then after three years I went up to Jerusalem to see Peter, and abode with him fifteen days. 19But other of the apostles saw I none, save James the Lord’s brother. 20Now the things which I write unto you, behold, before God, I lie not. 21Afterwards I came into the regions of Syria and Cilicia; 22And was unknown by face unto the churches of Judaea which were in Christ: 23But they had heard only, That he which persecuted us in times past now preacheth the faith which once he destroyed. 24And they glorified God in me.

... 6But of these who seemed to be somewhat, (whatsoever they were, it maketh no matter to me: God accepteth no man’s person:) for they who seemed to be somewhat in conference added nothing to me:

Comment: Paul, in the strongest terms, asserts the message he preaches was given to him personally by the resurrected Jesus. Paul builds the case for believing him on three facts. The first fact is that he preaches his message even if it isn't popular. It strains credulity to believe someone would preach an unpopular message for a messiah he didn't believe existed. The second fact that Paul points out is that his perspective had been completely reversed from what it was originally; from a person persecuting Christians to one evangelizing Christianity. Apparently this reversal was commonly known in the Christian community. The implication is that only encountering the resurrected Jesus would've been sufficient to change his life so dramatically. Finally, Paul points out that he preaches the same thing as the other apostles even though he had never been taught what to preach by them. The only way this could occur is if he had been taught by the same person as the original apostles even though he had not been one of Jesus' disciples prior to encountering the resurrected Jesus.