The man Saul of Tarsus was once a terrible name to the infant Church of Christ as he was noted to carry out torture and execution at least indirectly to those who believed, preached and lived the Gospel message of Jesus the Christ. One of these persecutions of the Church led to the martyrdom of the first Christian martyr called Stephen, a man described to be “full of faith and the Holy Spirit,” (Acts 6:5).
God in His perfect wisdom found a place for this man called Saul from Tarsus in His vineyard. By the grace of God, Saul became Paul as he experienced a life changing encounter with the Lamb of God, Jesus Christ Himself on his journey to Damascus to carry out similar persecution of the Church. (cf. Acts 9) Years later after this encounter with Christ, Paul became one of the most instrumental authors and figures of the New Testament, and a man of heroic virtue and extraordinary charism (gifts).
Although St. Paul was not among the original 12 Disciples of Christ, he is acknowledged as an Apostle of Christ and compared and even paired up with St. Peter the Prince of the Apostles. Many people mistakenly think that St. Paul wrote the Acts of the Apostles because of his other excellent New Testament writings/epistles. In fact, the author of the Gospel of Luke is the same person behind the Acts of the Apostles. Those two writings were addressed to a man named Theophilus (cf. Luke 1:3 and Acts 1:1).
In our days today, just as the days of the Apostles, many people have directly or indirectly pick-and-choose what to believe and what not to believe in the Gospel. The Gospel is the heart of the whole revealed truth of God to man. It is in the Gospel that the greatest miracle ever took place which involved God becoming man through what is historically called the Incarnation. It is in the Gospel that Jesus the God-Man taught us all we need to know about God and how to be pleasing to Him. It is in the Gospel that Jesus as the Bread of Life offered Himself freely that those who believe and eat His body and drink His blood will have everlasting life. It is in the Gospel that Jesus as the Messiah suffered for our sins and died for the whole world. It is in the Gospel that Jesus Christ resurrected from the dead. It is in the Gospel that Jesus Christ ascended into Heaven and stated that He would come again in glory to judge the living and the dead. It is in the Gospel that man is reconciled with God.
Just as many people treat the King James Version translation of the Bible (KJV) as though it were the original manuscript (MSS) of the Scriptures, so sadly too, many treat parts or whole of the writings of St. Paul as though it were the Gospel of Jesus Christ, or much worst contradictory or superior to the Gospel message found in Matthew, Mark, Luke and John. The letters of St. Paul are supplementary but not self-sufficient and independent from the Gospel of Christ.