2 Corinthians 11:16-29

I repeat: Let no one take me for a fool. But if you do, then receive me just as you would a fool, so that I may do a little boasting. In this self-confident boasting I am not talking as the Lord would, but as a fool. Since many are boasting in the way the world does, I too will boast. You gladly put up with fools since you are so wise! In fact, you even put up with anyone who enslaves you or exploits you or takes advantage of you or pushes himself forward or slaps you in the face.

(v16-20, NIV)

Boasting in yourself is wrong for the most part. This is because boasting in yourself is used to elevate yourself as the end goal. However, in this section, Paul is speaking as a fool in order to try and speak on the level of a fool. Since some of those at the Corinthian church have turned away to false gospels, they have become fools. Paul doesn't want to do this, but he is doing this in order to show them that even in their foolish way of thinking, Paul is superior to those they are following.

Though I am free and belong to no man, I make myself a slave to everyone, to win as many as possible. To the Jews I became like a Jew, to win the Jews. To those under the law I became like one under the law (though I myself am not under the law), so as to win those under the law. To those not having the law I became like one not having the law (though I am not free from God's law but am under Christ's law), so as to win those not having the law. To the weak I became weak, to win the weak. I have become all things to all men so that by all possible means I might save some. I do all this for the sake of the gospel, that I may share in its blessings.

(1 Corinthians 9:19-23, NIV)

Paul is becoming like those he is preaching to. In the same way he talks about becoming like a Jew to the Jews in 1 Corinthians 9:12-23, he is becoming like a fool to those at the Corinthian church in 2 Corinthians 11. In this case, his target audience is turning to false apostles. This turning reveals their foolishness. Paul is becoming a fool in order to reach out to them in a sense. He is trying to speak on their terms for them to understand. Sometimes we need to become like the people we are reaching out to. However, we should not sin in the process.

From verses 21 to 29 Paul lists out a bunch of his credentials. He is showing the ways he is superior to those other false apostles.

though I myself have reasons for such confidence.

If anyone else thinks he has reasons to put confidence in the flesh, I have more: circumcised on the eighth day, of the people of Israel, of the tribe of Benjamin, a Hebrew of Hebrews; in regard to the law, a Pharisee; as for zeal, persecuting the church; as for legalistic righteousness, faultless.

(Philippians 3:4-6, NIV)

Similarly, in Philippians, Paul lays out his credentials. However, in Philippians, he is laying out his credentials that would be highly viewed by Jews. To the Jew, he becomes a Jew.