Paul of Tarsus

Jewish-Christian apostle who wrote most of the New Testament epistles — Romans, Corinthians, Galatians — and whose theology of grace, justification by faith, and the universalism of the Gospel defined Christianity's transformation from a Jewish sect into a world religion.

Transformed Christianity from a Jewish sect into a universal religion — by arguing that faith in Christ's resurrection rather than observance of Jewish law was the basis of salvation — and created the theological categories (grace, sin, justification, resurrection) that define Christian doctrine.