Christian theology starts with the New Testament. Saint Paul, in his letters, and his speeches (Acts of the Apostles), draws upon his training as a rabbi and on his experience of Christ. He started outside Damascus to explain to Jews and Gentiles the meaning of the crucifixion and resurrection of Jesus. In the History of Christianity, later writers such as Luther and John Calvin have stressed the Bible as the basis of theology. The bible as a source is not without controversy. Catholic and Orthodox theologians have also stressed the importance of Church tradition for the faith. Thomas Aquinas and Saint Augustine are among the most important writers within the Roman Catholic Church.