"I knew a man in Christ above fourteen years ago, (whether in the body, I cannot tell; or whether out of the body, I cannot tell: God knoweth;) such an one caught up to the third heaven. And I knew such a man, (whether in the body, or out of the body, I cannot tell: God knoweth;)"
Although this text has been used to "prove" the doctrine of an immortal soul, it has no such connotation at all. It is conceded by practically all commentators that Paul was describing his own experience, because he spoke in the context of his own revelations. He was concerned that no one think he was glorying or boasting about his visions. For this reason, probably, he ascribed the experience to a man he knew.
Paul's soul did not leave his body, in spite of claims to the contrary. If so, he would have been dead, and nowhere does he make any allusion to his death or resurrection.
Paul is speaking of "visions" and "revelations" in the text. He was not puzzled over whether he had died or not. He was merely uncertain as to how he was able to see paradise in that vision. Although it seemed that he was bodily taken to heaven, yet he felt it possible that he was taken there only spiritually. He confessed to complete ignorance as to what actually happened. The physical impressions seemed as though He were "out of the body," in a way of speaking. In the same manner of speech, Paul wrote to the Colossian church, "For though I be absent in the flesh, yet am I with you in the spirit." Colossians 2:5. No one interprets this to mean that some immortal soul left Paul's body to be with his friends.
The fact is, as Paul said, that only God knows the nature of that spiritual visit to paradise. So we would do well not to base any doctrine on a text that is understood by God only.