How do traditional Christians defend the teaching that Paul is an authentic apostle?

When we go by Jesus' standard that you judge the tree by its fruit, then we have to credit Paul with the majority of the work that established Christianity among the Gentiles of the ancient world.

With that said, I don't believe that you have to consider Paul a "false Apostle" in order to believe that he was occasionally wrong. Paul himself warned the people he converted against idolizing him instead of turning their attention to Christ. Given that the apostles themselves didn't always agree with each other, I don't think it's a stretch to say that sometimes they were divinely inspired, and sometimes they weren't.

In addition, Paul was clearly called primarily as an evangelist, but evangelism is only one part of the work Jesus establishes for Christians in the Gospels. There's a danger that if you only read the Pauline Epistles, you only receive a portion of the Christian message.

It is a very relevant question you ask here. Occasionally, someone from the Jesus seminar, for instance, will make the claim that Paul somehow stole Christianity away from the apostles and his disagreement with the Jewish Christians was never resolved. For example, the 2006 Peter Jennings documentary "The Search for Jesus" had an expert biblical scholar making this claim.

Here is just some more circumstantial evidence from a non-canonical source to add to the other answers. The bishop of Rome, Clement, wrote a letter to the Church in Corinth in the late 1st century which is regarded by most scholars as authentic. There is a passage where he is talking about Peter and Paul who had been martyred 'in our generation'.

The take away here is that it seems that both Peter and Paul were contemporaries, ministering in Rome at the same time. More than likely they were ministering together building the very early church in Rome.

This is not 'the' answer, you can make an argument against it. But taken together with the other evidence, it makes a good case that Paul did not have any lasting disagreements or schisms, theological or otherwise, from the other Apostles.

My answer to question this isn't based on Bible verses, But based on my overall view of his life.

Luke wrote in detail about the Missions of Paul in Acts. The suffering of Paul in his entire life leaves me doubtless on the life of Paul. Luke humbly hides himself, since he wanted us to focus on the great Apostleship of Paul. So I can't think that Paul was an insidious infiltrator, His death reveals us that he was a martyr.

Regarding his conversion, there were witnesses, and the whole event was recorded by Luke.

Other apostles didn't write or say anything wrong about Paul's preaching or find fault on him.

Finally, His entire message doesn't complicate our believes, It reflects what the old testament says, and what Jesus said.

>>I don't hold the position that he is a false Apostle

Paul most certainly was not a false apostle. His epistles show he suffered greatly in order to help spread Christianity among the gentiles and, according to tradition, died for it.

• Maybe he thought that if he got to be an insider with influence, he could corrupt the teachings from the inside?

But what would he gain by this? Christianity spread through his efforts. And I will show that his theology was in no way corrupt, particularly in regard to faith and works.

• Next, nobody witnessed his conversion. He was on the road alone, and we have only his word for it. Nobody can verify his claims.

Paul never claimed to have been converted on the road to Damascus - that comes solely from Acts of the Apostles, where there are three different versions of the event. We may not know why the author of Acts believed that Paul experienced a vision of Jesus on the road to Damascus, but certain aspects associated with this seem contradicted by Paul in his own epistles. Regardless of the historicity of the conversion account in Acts, Paul only claimed that it pleased God to reveal his son "in me," after which he conferred with no one but went immediately to Arabia (Galatians 1:16-17).

• his teachings on salvation apart from works seems to contradict other clear teachings

In his undisputed epistles, Paul taught that salvation is achieved by faith without works of the (Jewish) law. In these epistles, he preached that faith in Jesus was of the utmost importance but did not say that good works are not also necessary, in fact frequently preaching against sin and for good works.

Bart D. Ehrman says in Forged, page 99, that Paul was very concerned with arguing that performing the ‘works of the law’ could not contribute to one's right standing before God. For him, it was not the Jewish law that could bring salvation, but the death and resurrection of Jesus. Ehrman insists that When Paul talks about ‘works’, he means doing the things that the Jewish law requires, such as getting circumcised, keeping kosher, and observing the Sabbath. For example, reading Romans 3:27 in isolation could lead to the conclusion that Paul rejected salvation through works - until we read on, to verses 28-29, where we see in context that in "By what law? of works?" he was referring to the Jewish law:

27 Where is boasting then? It is excluded. By what law? of works? Nay: but by the law of faith.

28 Therefore we conclude that a man is justified by faith without the deeds of the law. Is he the God of the Jews only? is he not also of the Gentiles? Yes, of the Gentiles also:

In Romans 4:1-5,9-10 Paul says that Abraham was judged righteous by his faith in God (his willingness to obey a command to sacrifice his son), not because he was or was not circumcised:

What shall we say then that Abraham our father, as pertaining to the flesh, hath found? For if Abraham were justified by works, he hath whereof to glory; but not before God. For what saith the scripture? Abraham believed God, and it was counted unto him for righteousness. Now to him that worketh is the reward not reckoned of grace, but of debt. But to him that worketh not, but believeth on him that justifieth the ungodly, his faith is counted for righteousness . . . Cometh this blessedness then upon the circumcision only, or upon the uncircumcision also? for we say that faith was reckoned to Abraham for righteousness. How was it then reckoned? when he was in circumcision, or in uncircumcision? Not in circumcision, but in uncircumcision.

Ehrman says (page 197) the author of the Epistle to the Ephesians transformed Paul’s teaching that the works of the Jewish law could not bring salvation into a teaching that said good works could not save. Ephesians 2:8-9 certainly seems a direct contradiction to what Paul said in Romans and other undisputed epistles, clearly stating that salvation is by faith and (lest any man should boast) not by works "of yourself," but we should not judge Paul by this epistle, which the majority of critical scholars say was written in Paul's name sometime in the 80s of the first century:

Ephesians 2:8-9: For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: Not of works, lest any man should boast.

Burton L. Mack says in Who Wrote the New Testament, page 214, that the Epistle of James was written partly as a response to the teachings of Paul, but is reacting not to what Paul said but to what later Christians, especially the author of Ephesians, misunderstood Paul as saying:

James 2:14-17: What doth it profit, my brethren, though a man say he hath faith, and have not works? can faith save him? If a brother or sister be naked, and destitute of daily food, And one of you say unto them, Depart in peace, be ye warmed and filled; notwithstanding ye give them not those things which are needful to the body; what doth it profit? Even so faith, if it hath not works, is dead, being alone.

James 2:24 Ye see then how that by works a man is justified, and not by faith only.

Paul's teachings on faith and good works were on song, but have been misunderstood because of the pseudepigraphical epistles, especially Ephesians.

Warren has already noted that the apostle Peter vouched for Paul's authenticity and a_hardin noted that there were other witnesses to his conversion and life before and after. We could continue with these references of people that vouched for him personally.

Another approach can also be taken. An interesting thought experiment can be played by taking Paul and all his writings out of the Bible. While it's true he penned large chunks of the New Testament, he didn't pen it all. The four gospels and not a few letters were from other authors, some of them Jesus' original disciples. In fact, for the sake of this experiment, you could set aside things like Revelation and the other late letters and just work with the historical accounts of Jesus. The Gospels make little attempt to teach what the church should look like (or teach anything at all) they are primarily a historical narrative of Jesus' life and teachings.

Now step back to the Old Testament for a minute. Think about all the things we learn about God and His plan of salvation from it. From Genesis we find the fall of man and the promise of a Savior, then through every generation we have a record of how God interacted with His people and what He required of them. Through the prophets we get a picture of what the savior was to look like.

Admittedly this wasn't very well understood: the Jews didn't instantly recognize Jesus as fulfilling these. Yet through the account of the Gospels we come to an understanding that He did. We know from Him what salvation looks like, what it looks like to follow Him. We know about the sacrifice He made, the propitiation that His death was, what repentance and grace look like, that He came to fulfill the law not abolish it, and so on.

Without continuing on to Paul's letters, we already have everything we need to know for Christianity to be what it is. If we believe the testimony about what Jesus taught, we have the basics solidified. Continuing on to Paul and the teachings of the other apostles after He left, we don't learn anything new or different, we only get an expounded view and implementation of the things we already learned. We get their (inspired) commentary and interpretation, but we don't get any changes. Nothing taught by Paul contradicts the OT or Jesus' teachings or even goes so far beyond them that we couldn't reason out the same conclusions from other material.

I think we owe Paul a huge debt for his faithful contribution. He was a tool used by God to communicate timeless truths to the early NT church and to us today, but our faith is not built on Paul. We are Christians, not Paulinians. I believe that his written testimonies in Scripture carry unique authority as an Apostle writing at a time when other living disciples of Christ vouched for him as a specially chosen and anointed apostle, still we don't have to depend on him alone for any of our major doctrines.

The Apostle Peter believed him to be "authentic":

Therefore, beloved, since you look for these things, be diligent to be found by Him in peace, spotless and blameless, and regard the patience of our Lord as salvation; just as also our beloved brother Paul, according to the wisdom given him, wrote to you, as also in all his letters, speaking in them of these things, in which are some things hard to understand, which the untaught and unstable distort, as they do also the rest of the Scriptures, to their own destruction.

On top of this, we also have the direct revelation to Ananias of Damascus regarding Paul's conversion:

Now there was a disciple at Damascus named Ananias; and the Lord said to him in a vision, "Ananias." And he said, "Here I am, Lord." And the Lord said to him, "Get up and go to the street called Straight, and inquire at the house of Judas for a man from Tarsus named Saul, for he is praying, and he has seen in a vision a man named Ananias come in and lay his hands on him, so that he might regain his sight." But Ananias answered, "Lord, I have heard from many about this man, how much harm he did to Your saints at Jerusalem; and here he has authority from the chief priests to bind all who call on Your name." But the Lord said to him, "Go, for he is a chosen instrument of Mine, to bear My name before the Gentiles and kings and the sons of Israel; for I will show him how much he must suffer for My name's sake." So Ananias departed and entered the house, and after laying his hands on him said, "Brother Saul, the Lord Jesus, who appeared to you on the road by which you were coming, has sent me so that you may regain your sight and be filled with the Holy Spirit." And immediately there fell from his eyes something like scales, and he regained his sight, and he got up and was baptized; and he took food and was strengthened.