This is a excerpt from a talk by a Tom Brown.... Its good.
Three Errors
The accustomed interpretation in traditional Christianity concerning this passage is as follows: Paul was prideful because of the great revelations God gave him. To keep Paul humble God sent a demon to make him sick. Paul asked God to heal him, but the Lord said no. The lesson: God sometimes sends demons to make us sick in order to keep us humble.
Satan is cunning. He can distort any Scripture to keep people bound. This passage is a case in point.
There are three major errors concerning this traditional interpretation: first, that God personally sent the demon, second, that the demon made Paul sick, and third, that God refused to heal Paul from this sickness.
Exalted Beyond Measure
Paul gives the reason why this messenger of Satan was given to him. "Lest I should be exalted above measure through the abundance of revelations."I find it inconsistent that people claim to have Paul’s thorn but they don’t claim to have his abundance of revelations. So before you claim to have a thorn, make sure you have an abundance of revelations.
Paul says, "there was given to me a thorn in the flesh, the messenger of Satan to buffet me."Since Paul uses the word given people assume that God gave it. But notice that the thorn in the flesh is a messenger of Satan. Messengers are sent from their leaders. This messenger was sent by his leader, Satan. God did not send him.
What did this messenger of Satan do? Many think that this messenger was a demon who made Paul sick. They assume this demon made him sick because in the gospels we find demons causing sicknesses. But this is not the only thing that demons do. They also cause persecutions. This is what this evil spirit caused. Let me prove this to you.
Let the Bible Interpret Itself
The first rule of Bible interpretation is this: if at all possible, let the Bible interpret itself. In other words, before you give a meaning to a passage, ask yourself if there are any other Scriptures related to this. If there are, then let those passages interpret the passage you’re reading. This is especially true concerning Paul’s thorn.
To understand what problem the messenger of Satan caused, you have to understand the term "thorn in the flesh." This term is found frequently in the Old Testament. Paul was very familiar with the Old Testament, so he undoubtedly used this term in the same way that it is used in the Old Covenant.
It’s amazing to me that people speculate as to the meaning of Paul’s thorn. Most theologians will say, "We can’t be sure what this thorn was, but it was probably a sickness, perhaps an eye disease."
When I hear this kind of speculation I wonder if these so-called experts have bothered to look up the word thorn in their concordance. If they had, then they would know for sure what Paul’s thorn really was.
So what was this thorn? You have the answer if you know how the word thorn was used in the Old Testament. Once you know, then you know the meaning of Paul’s thorn.
There are three main passages in the Old Testament that relate to Paul’s thorn in the flesh. The first one is Numbers 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."
So here, the thorns represent Israel’s enemies—those who caused trouble for Israel. The second passage which refers to thorns is Judges 2:3:
"Now therefore I tell you that I will not drive them out before you; they will be thorns in your sides and their gods will be a snare to you."
The thorns were the Canaanites. The Canaanites were Israel’s persecutors. Again we see that the thorns referred to people who hated Israel. The third passage about thorns is Joshua 23:12-13:
"But if you turn away and ally yourselves with the survivors of these nations…then you may be sure that the Lord your God will no longer drive out these nations before you. Instead, they will become snares and traps for you, whips on your backs and thorns in your eyes, until you perish from this good land, which the Lord your God has given you.
This passage makes it plain that the nations were going to be thorns in Israel’s eyes.
Put these three passages together and you discover what the thorns represent. The thorns consistently represent Israel’s enemies. They were Israel’s persecutors. Not once does the Bible use this term thorn to represent physical sicknesses.
Go back to the passage in 2 Corinthians and you see that Paul’s thorn represented his enemies who persecuted him. This is obviously what he had in mind, because he mentions clearly what the thorn did to him:
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. (2 Corinthians 12:10)
It doesn’t take a genius to figure out that Paul used the term thorn to represent persecutions (and all that went with it) that he endured for preaching the gospel. To suggest that Paul’s thorn was an organic illness, such as Ophthalmia, is really stretching the meaning of this term. The Bible plainly tells us that the term thorn is used in reference to people who become enemies of God’s family. This is what Paul meant by that term.
Even today, we have a similar term which means the same thing. We say that someone is a "pain in the neck." We don’t actually mean that we have a physical pain. The term pain in the neck is a colloquial phrase which conveys that someone is giving us problems. The term thorn in the flesh does not mean an actual thorn or an actual fleshly problem. It simply means that people harassed Paul.
Again there is a difference between Word and doctrine