Election
He was elected during a lull in the persecution under Emperor Decius, probably due to the emperor's absence. Due to strong disagreements over the readmittance of lapsed Christians, his election was opposed by Antipope Novatianus (251), who was later elected as pope by his supporters.Forgiveness of grave sins
In the controversy of forgiveness of sins, Cornelius supported that priests could forgive grave sins (adultery, murder, etc) of those asking to return to the church. He excommunicated Novatianus.Death
Under Emperor Trebonianus Gallus, he was exiled to Centuricellae, where he later died.249-251: Roman Emperor, Trajan Decius
251: Antipope Novatianus
251-253: Roman Emperor, Gallus
251-253: Roman Emperor, Volusianus
253: Roman Emperor, Aemilianus
253-260: Roman Emperor, Valerian
253-268: Roman Emperor, Gallienus