I have heard many different thoughts as to what Paul's "thorn in the side" is, that is to keep him humble. The infirmity that he prayed three times to remove, but the Lord told him it had a purpose for it, etc. I have heard it was a speech impediment, or possibly an ugly growth on his face that made him hard to look at. I tend to believe that it was something very painful. I may be wrong, but it would be my guess that this would humble Paul. Then again, so would a lack of being able to speak of his revelations well. But, we know he taught in synagogues, so this doesn't seem likely. Are there any other historical writings that refer to Paul's infirmity and/or early church fathers that have mentioned it in their writings, that would be believeable?