What does 2 Corinthians 12:19 mean?

Paul has spent much of this letter countering attacks on his character and his role as an apostle of Jesus Christ. These attacks have come from false apostles in Corinth, as well as some of the Corinthians themselves. Paul now asks what may be a surprising question: Have you been reading this letter as if we—meaning Paul and his associates—are defending ourselves to you? It certainly seems like that's what Paul has been doing.

Of course, Paul has presented a long list of defenses. The key phrase in the question is "to you," meaning the real issue to whom Paul is accountable. In the most important sense, Paul does not need to defend himself to the Corinthians. They are not his judge and jury. He has been countering the attacks against him in the sight of God. Paul understands God to be his only judge. He has been speaking in Christ, fully secure in his legitimate role as an apostle of Jesus to the Corinthians.

The reason he has worked hard to counter lies about him, Paul writes, is for their sake, in order to build them up. He calls them his beloved. He has been waging this war of words in order to persuade them that what he taught them about Christ is trustworthy and true. He doesn't want them to be led away from Christ and into sin by these false teachers. If he needs to stand up for himself in order to save them, he will do it.