May have been born a slave. May have been the brother of Hermas, author of The Shepherd. Tenth Pope. Reportedly established the date for Easter as the first Sunday after the March full moon. Established rules for the conversion of Jews. Opposed Marcion the agnostic. May have been martyred.
The fact that Saint Justin Martyr did his Christian teaching in Rome, Italy, and that the three heretics Valentinus, Cerdon, and Marcion visited there, help prove that at even this early in the Church‘s history, Rome was already the primary see and the center of its authority.