The judgment that one forms of the theory and practice of penance in Christian antiquity will be largely determined by the interpretation which one puts upon these two treatises. On Penitence dates from Tertullian's Catholic period, and is a sermon addressed to the faithful on the subject of repentance and forgiveness. On Purity is one of his most violent Montanist treatises. In it he criticizes the policy the Church follows in granting pardon to serious sins.