St Paul’s conversion to Christianity transformed a vicious persecutor of Christians into one of the most important and influential figures in the foundation of the early church. Paul’s broad theological knowledge and his ambitious vision for the faith made him a major force in the development of Christianity from its origins as an obscure Jewish sect. W. L. Knox’s 1925 biography examines what influenced Paul’s theological ideas and how his desire to extend the church’s reach to gentiles and the wider world put him in opposition with other early church figures like St Peter. Placing Paul’s work in the social and religious context of Jerusalem following the death of Jesus, Knox evokes the atmosphere of persecution in Jerusalem and the inner social dynamics of the early Christian sect, evaluating Paul’s impact on the growing church and the particular ideas and elements of doctrine that prevailed as a result of his involvement.