United Against Heresy, United in Martyrdom St. Cornelius, Bishop of Rome from 251 to 253 AD, lived during a turbulent time for the early Catholic Church. The Novatian heresy, which originated with the Roman priest Novatian, claimed that the Church could not offer forgiveness to Christians who had lapsed in their faith under persecution. This was in direct opposition to the Church's teaching on repentance and mercy.