Callistus (217–222) readmitted penitent members who had committed adultery. He argued that the church is like Noah’s ark. In it unclean as well as clean beasts can be found. Then he defended his actions by insisting that the church of Rome was the heir of Peter and the Lord had given keys to Peter to bind and to loose the sins of men. This marks the first time a bishop of Rome claimed this special authority.
