Acts 9: 3 "And as he journeyed, he came near Damascus: and suddenly there shined round about him a light from heaven:
5 And he said, Who art thou, Lord? And the Lord said, I am Jesus whom thou persecutest: it is hard for thee to kick against the pricks.
6 And he trembling and astonished said, Lord, what wilt thou have me to do? And the Lord said unto him, Arise, and go into the city, and it shall be told thee what thou must do."
Saul, now blind, was taken to Damascus. After 3 days of fasting, he was visited by a disciple whom the Lord sent to restore his sight. Saul was baptized and became as fervent a follower and preacher of Christ as he had previously been a persecuter of Christ's followers.
Why was a man who sought to destroy the church given a vision and brought to the Lord? Why did he get special attention and special treatment? Why isn't everyone given a vision to bring them to the Lord? Wouldn't anyone be converted if they had an experience like Saul's?
No, others have had heavenly manifestations and not been converted. I think of Laman and Lemuel in the Book of Mormon. They had been taught by their father and by their brother but they chose not to believe. An angel rebuked them for beating their brother and not doing the errand their father had been commanded to set them. No sooner had the angel left, then they started complaining that they could not do the task. Many times they were shaken or shocked by the power of God when they tried to harm their brother, Nephi. Each time they seemed quite impressed but quickly forgot and were never truly converted to following the commandments. So, one can have heavenly manifestations and still reject the Lord.
I think the difference was that Saul was sincere in his actions and intent. He was true to the light as he understood it. He rigorously defended what he thought was true religion. He acted zealously out of love for God, but was misguided. Once the Lord pointed out his error, he did a complete turn around and just as rigorously sought to live and teach the gospel of Jesus Christ.
Secondly, Saul was causing havoc amongst the followers of Christ. His conversion brought peace to the church making it easier for the gospel to spread. But I think the main thing is that Saul's intent was always to serve God which made him convert-able, although maybe a little hard of hearing so he got the big show.
Do we need a major heavenly manifestation to believe? The Lord whispers to us constantly, but do we listen? We have the scriptures, the testimonies of others, and even the evidence of the wonders of the earth and the universe.
Alma 30: 44 "But Alma said unto him: Thou hast had signs enough; will ye tempt your God? Will ye say, Show unto me a sign, when ye have the testimony of all these thy brethren, and also all the holy prophets? The scriptures are laid before thee, yea, and all things denote there is a God; yea, even the earth, and all things that are upon the face of it, yea, and its motion, yea, and also all the planets which move in their regular form do witness that there is a Supreme Creator."
If we learn to listen, we can be converted as thoroughly as Saul.