In answer to Winman's post, you don't allow for any other possibility. Yes, you say the "Lord struck him down and changed him."
But Saul said: "What will thou have me to do."
His response was not: "I am not going to do thy will; I am not going to bow down to this so-called Messiah."
He had that choice. He could have gone either way. But you won't admit that.
Yes, Paul had in fact heard the gospel before and resisted, he was the witness when Stephen was stoned.
Acts 7:57 Then they cried out with a loud voice, and stopped their ears, and ran upon him with one accord, 58 And cast him out of the city, and stoned him: and the witnesses laid down their clothes at a young man's feet, whose name was Saul.
Paul heard Stephen and he was one of those who cried with a loud voice and covered their ears that they might not hear his words.
That is resisting the Holy Ghost. And Paul continued to resist for some time, and made havock of the church (Acts 8:1-4).