2 Corinthians 12New International Version (NIV)
Paul’s Vision and His Thorn
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 vision on the road to hunt down more followers of Christ, and other heavenly visions was probably cause by temporal lobe epilepsy. Also notice Paul mock humility which he fools himself and others who accept his offered credentials.
Paul's temporal lobe epilepsy explained:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1032067/pdf/jnnpsyc00553-0001.pdf