We saw how Paul defended his ministry to the Corinthians last week. Pointing not to what he had accomplished but only to the things God had done.
2 Corinthians10 17 But, ‘Let the one who boasts boast in the Lord.’ 18 For it is not the one who commends himself who is approved, but the one whom the Lord commends.
Paul was countering the “super-apostles” who were leading the Church in Corinth astray, as Eve herself was by the devil in the Garden of Eden. These super-apostles were actually preaching a different gospel
11 . 4 For if someone comes to you and preaches a Jesus other than the Jesus we preached, or if you receive a different spirit from the Spirit you received, or a different gospel from the one you accepted, you put up with it easily enough

In particular it seems that they were criticizing Paul because he supported himself during his time in Corinth, rather than expecting the Corinthians to give him hospitality and pay all his bills. 9…. I have kept myself from being a burden to you in any way, and will continue to do so.

And Paul goes on to be even more direct in his criticisms.
13 For such people are false apostles, deceitful workers, masquerading as apostles of Christ. 14 And no wonder, for Satan himself masquerades as an angel of light. 15 It is not surprising, then, if his servants also masquerade as servants of righteousness. Their end will be what their actions deserve.
We saw last week how Paul summed up his defence against the “super-apostles”.
2 Corinthians 12 11 …. I am not in the least inferior to the ‘super-apostles’, even though I am nothing. 12 I persevered in demonstrating among you the marks of a true apostle, including signs, wonders and miracles.
These, says Paul, are included in the marks of a true apostle . and they were evidenced in Paul’s own ministry time and time again. Not boasting of their own accomplishments. Faithfully preaching the gospel as Christ commands all his followers to do. Not sponging off gullible Christians as some celebrity evangelists and preachers do today exploiting their followers. Not deceitful workers, masquerading as angels of light. But manifesting signs and wonders and miracles. That was last week. This week we come back to three more grounds Paul used in those chapters to defend his ministry which we skimmed over last week. They are often grouped together because they have a similar theme, and some people call them collectively “The Fool’s Speech”.
2 Corinthians 11 16 I repeat: let no one take me for a fool. But if you do, then tolerate me just as you would a fool, so that I may do a little boasting. 17 In this self-confident boasting I am not talking as the Lord would, but as a fool. 18 Since many are boasting in the way the world does, I too will boast. 19 You gladly put up with fools since you are so wise! 20 In fact, you even put up with anyone who enslaves you or exploits you or takes advantage of you or puts on airs or slaps you in the face. 21 To my shame I admit that we were too weak for that!
Paul says that he is speaking like a fool. Not because he is a fool – but because the evidence he calls on to defend his ministry and his mission could be interpreted as evidence that he is a fool. He starts by pointing to his background.
Whatever anyone else dares to boast about—I am speaking as a fool—I also dare to boast about. 22 Are they Hebrews? So am I. Are they Israelites? So am I. Are they Abraham’s descendants? So am I.

But then Paul goes on to talk about his experiences of suffering for Christ. He starts with his experiences of persecution

23 Are they servants of Christ? (I am out of my mind to talk like this.) I am more. I have worked much harder, been in prison more frequently, been flogged more severely, and been exposed to death again and again. 24 Five times I received from the Jews the forty lashes minus one. 25 Three times I was beaten with rods, once I was pelted with stones.

These sufferings came to Paul in persecution for his faithful preaching of the gospel. Then he goes on to list other perils he had faced on his missionary journeys.

25 … three times I was shipwrecked, I spent a night and a day in the open sea, 26 I have been constantly on the move. I have been in danger from rivers, in danger from bandits, in danger from my fellow Jews, in danger from Gentiles; in danger in the city, in danger in the country, in danger at sea; and in danger from false believers.

On top of all these dangers he had experienced, Paul had also endured a great many discomforts and inconveniences. He had made many sacrifices following Jesus.

27 I have laboured and toiled and have often gone without sleep; I have known hunger and thirst and have often gone without food; I have been cold and naked. 28 Besides everything else, I face daily the pressure of my concern for all the churches. 29 Who is weak, and I do not feel weak? Who is led into sin, and I do not inwardly burn?

So as evidence that he is a true apostle, Paul points to the mark of suffering for Christ, the servant King. Jesus had warned the apostles that they would suffer opposition and persecution. Ten out of the Eleven Apostles were martyred. Unlike the false “super-apostles” who enjoyed a life of luxury at the Corinthians’ expense, Paul’s true apostleship was evidenced by his suffering. And this will be the destiny of missionaries and evangelists and ministers in every age. Although it may seem foolish to some people, suffering for Christ is not a sign of failure in ministry but a mark of true ministers. Paul sums up that strand with a recollection of a particular event which demonstrates not impressive strength but humble weakness.

30 If I must boast, I will boast of the things that show my weakness. 31 The God and Father of the Lord Jesus, who is to be praised for ever, knows that I am not lying. 32 In Damascus the governor under King Aretas had the city of the Damascenes guarded in order to arrest me. 33 But I was lowered in a basket from a window in the wall and slipped through his hands.

The true servant of God will suffer for Christ. Paul had already pointed out to the Corinthians this inherent foolishness of the gospel in his first letter to them.

1 Corinthians 1 27 But God chose the foolish things of the world to shame the wise; God chose the weak things of the world to shame the strong. 28 He chose the lowly things of this world and the despised things—and the things that are not—to nullify the things that are, 29 so that no one may boast before him. 30 It is because of him that you are in Christ Jesus, who has become for us wisdom from God—that is, our righteousness, holiness and redemption. 31 Therefore, as it is written: “Let him who boasts boast in the Lord.”
God uses foolish things and weak things to shame the strong. The heart of the gospel is the foolishness of the cross of Christ. So here is one mark of the true apostle – suffering for Christ. And then Paul goes on to a second demonstration of his ministry – his experiences of visions and revelations, which are evidence that the Spirit who inspired the prophets had been poured out on him in abundance. Paul personally had many experiences of prophecy, of dreams and visions. It was his vision of a Man from Macedonia in Acts 16 which led Paul to preach the gospel there. It was actually while he was staying in Corinth that Paul faced fierce persecution and we read in Acts 18 about a vision he had there.
Acts 18 9 One night the Lord spoke to Paul in a vision: ‘Do not be afraid; keep on speaking, do not be silent. 10 For I am with you, and no one is going to attack and harm you, because I have many people in this city.’ 11 So Paul stayed in Corinth for a year and a half, teaching them the word of God.
Paul had many experiences of dreams and visions and next he refers back to some of these.
12 I must go on boasting. Although there is nothing to be gained, I will go on to visions and revelations from the Lord. 2 I know a man in Christ who fourteen years ago was caught up to the third heaven. Whether it was in the body or out of the body I do not know—God knows. 3 And I know that this man—whether in the body or apart from the body I do not know, but God knows—4 was caught up to paradise and heard inexpressible things, things that no one is permitted to tell. 5 I will boast about a man like that, but I will not boast about myself, except about my weaknesses. 6 Even if I should choose to boast, I would not be a fool, because I would be speaking the truth. But I refrain, so no one will think more of me than is warranted by what I do or say, 7 or because of these surpassingly great revelations.
Paul was blessed by wonderful visions and revelations. But actually he doesn’t boast about them. He doesn’t go into details of what he saw. Those visions were just for him. He isn’t even allowed to talk about them. But they led on to a third strand in Paul’s defence.
. 6 Even if I should choose to boast, I would not be a fool, because I would be speaking the truth. But I refrain, so no one will think more of me than is warranted by what I do or say, 7 or because of these surpassingly great revelations. Therefore, in order to keep me from becoming conceited, I was given a thorn in my flesh, a messenger of Satan, to torment me. 8 Three times I pleaded with the Lord to take it away from me. 9 But he said to me, ‘My grace is sufficient for you, for my power is made perfect in weakness.’

What was Paul’s “thorn in the flesh”? Most commentators agree that we can’t know what for sure. But many think that Paul was referring once again here to his experiences of persecution. In the Old Testament the idea of a thorn in the side was used to describe the surrounding nations which opposed God’s chosen people Israel and tried to lead them astray from following God.
Num 33:55 | “ ‘But if you do not drive out the inhabitants of the land, those you allow to remain will become barbs in your eyes and thorns in your sides. They will give you trouble in the land where you will live.

Eze 28:24 | “ ‘No longer will the people of Israel have malicious neighbors who are painful briers and sharp thorns. Then they will know that I am the Sovereign LORD.

If Paul’s thorn was some experience of persecution then perhaps he was referring to those people who opposed him, maybe specifically those in Corinth, either the vocal critic who had opposed him in person referred to earlier in the letter, or the “super-apostles” themselves.
Other views see Paul’s thorn in the flesh, that is in his mortal body, as some kind of illness. Paul wrote this to the Galatians.
Galatians 4 13 As you know, it was because of an illness that I first preached the gospel to you. 14 Even though my illness was a trial to you, you did not treat me with contempt or scorn. Instead, you welcomed me as if I were an angel of God, as if I were Christ Jesus himself.
So arriving in Galatia Paul experienced some kind of illness or infirmity. Perhaps this became a recurring interruption and interference to his ministry. Others think Galatians 6 gives us insight into this question. Paul used an amanuensis, a secretary, to dictate most parts of his letters. But he signs off Galatians himself like this.
Gal 6 11 See what large letters I use as I write to you with my own hand!
The large letters lead some people to think that Paul was actually very short-sighted. If so, this could also have contributed to his overall demeanour with the result that some people thought he was very unimpressive in person.
Experiences of persecution, or some kind of ailment? Nobody knows what Paul’s “thorn in the flesh” actually was. But we do know why God allowed Paul to go through times of suffering in that way.
Therefore, in order to keep me from becoming conceited, I was given a thorn in my flesh, a messenger of Satan, to torment me.
Paul is very clear that alongside the amazing revelations, God allowed him to suffer this “thorn” precisely in order to keep him humble. When we are suffering, either through opposition or rejection or through physical illness, we always race to ask God to take the suffering away. But we should also ask God whether there he has some purpose in allowing us to suffer. Sometimes there won’t be any purpose we will discover in this life or the next. But sometimes there will be. God will sometimes allow Christians to go through suffering, because he has something to teach us. We can find ourselves grumbling about our illnesses or our experiences of opposition, instead of learning the lesson God has for us in them.
But as well as keeping him humble, Paul’s thorn in the flesh brought him another blessing. It taught him to trust in God.
8 Three times I pleaded with the Lord to take it away from me. 9 But he said to me, ‘My grace is sufficient for you, for my power is made perfect in weakness.’
Whether persecution or illness, this thorn taught Paul to find his strength not in himself, but in God. Not by might, nor by power, but by my Spirit says the Lord Almighty (Zechariah 4:6). It might seem foolish that Paul would defend his ministry by pointing out his own weaknesses. But in fact they were a mark of his apostleship because through them God’s strength had been revealed. Here in a verse is a clear rebuke to the false gospel of health, wealth and prosperity which is taking hold in so many places today and may have been the error embraced by the false “super-apostles”. God does not guarantee Christians victory in every situation. He does not promise physical healing to everyone. Quite the reverse.
9 But he said to me, ‘My grace is sufficient for you, for my power is made perfect in weakness.’ Therefore I will boast all the more gladly about my weaknesses, so that Christ’s power may rest on me. 10 That is why, for Christ’s sake, I delight in weaknesses, in insults, in hardships, in persecutions, in difficulties. For when I am weak, then I am strong
Here is Paul’s defence of his ministry. The evidence of suffering persecution for following the Crucified Christ. The evidence of visions and revelations. The evidence of weakness, depending on God’s strength for everything. These were the marks of the apostle to the Gentiles and the marks of true ministers and missionaries and evangelists through the ages and today.