God revealed his Son in Paul not merely to him. Paul knew that this was a revelation not just to his five senses, for the certainty with which Christ is revealed to us at the new birth is greater than anything that results from an empirical enquiry.
To have Christ revealed in our hearts is to know that he is our God, that he was without sin, that he came to earth to give his life for our offenses, and was raised again for our justification. It is to see his grace in such a way that we are never the same again, for the Spirit shows us our sinfulness and our need, and then leads us to the only one who can satisfy that need. We have looked into the face of Christ. We know that such a one exists and cannot be defeated because he has conquered death. He has given himself in an act of grace which overcomes all human meanness, and can melt the hardest of hearts.