As time passed, Saul’s confidence grew stronger and stronger, so much so that he debated with the Jews of Damascus and made an irrefutable case that Jesus is, in fact, God’s Anointed, the Liberating King. Acts 9:22 (The Voice, emphasis mine)
Soon after Saul’s Damascus Road experience he begins his new ministry in earnest. We can imagine the surprise and understand the initial mistrust of those he set out to persecute, when he instead rises to defend Jesus and proclaim Him as our Liberator. What enabled Saul, later to be Paul, to step into his new role and purpose so quickly and so powerfully?
The easy answer is in part that his newfound faith and the Holy Spirit flooded him, giving him the strength of zeal on the heels of his conversion. In that he is not so different from many who have just recently had their conversion experience. There are two additional factors which I believe set Paul apart from most others, however, his mind and his obedience.
We know that Paul was a learned man, a scholar of scripture, the law, and his times. Paul’s confidence grew precisely because he was an intellect. As such, he would have had to be convinced not only by his miraculous experience, but also by proving its veracity through scripture. He was an intellectual who possessed the integrity needed to search for Truth, not just accept as truth what he had been taught. His confidence grew from the union of his heart and mind.
This confidence, born of his diligent testing of the Word and his experience, and probably the strength of his academic reputation, enabled him to stand face to face with unbelievers to make an irrefutable case, one that cannot be denied with any seriousness. The Jews of Damascus didn’t like it, but they couldn’t disprove it either. Thus, the plot to assassinate Paul (vs 23-26).
Here is the thing: We are called to great faith, the same faith that Paul exhibited, faith that enables us to stand with confidence for Truth. We are also called to defend our faith against the apostasies of our world. In pursuit of these callings we require the same strengths that Paul had: Strength of confidence and strength of mind. It is not enough to know intrinsically that Jesus is Lord and Savior, although that is certainly a prerequisite. We must also be able to defend Truth with Knowledge, Understanding, and Wisdom that which the Holy Spirit has placed inside of us. Paul was obedient, and his confidence grew with his faith as he exercised the mind God gifted him with. The spirit connection matters, but we must also be able to prove its position, purpose, and power in our lives.
Faith in our hearts, the presence of the Holy Spirit, strength of mind and conviction, and obedience in exercising each of these in concert. This is the calling upon every believer, and the measure of our daily walk.
 The two names are generally used interchangeably. Scripture first records his name as Paul when he is on Cyprus. See Acts 13:9