Novatianism was an Early Christian sect devoted to the theologian Novatian (c. 200-258) that held a strict view that refused readmission to communion of lapsi (those baptized Christians who had denied their faith or performed the formalities of a ritual sacrifice to the pagan gods under the pressures of the persecution sanctioned by Emperor Decius in AD 250). The Church of Rome declared the Novatianists heretical following the letters of Saint Cyprian of Carthage. Novatianism survived until the 8th century
After the martyrdom of Pope Fabian during the Decian persecution, a Roman priest, Novatian, opposed the election of Pope Cornelius in 251, on the grounds that Cornelius was too liberal in accepting lapsed Christians. Novatian held that lapsed Christians, who had not maintained their confession of faith under persecution, may not be received again into communion with the church. He was consecrated bishop by three bishops of Italy and declared himself to be the true Pope. He and his followers were excommunicated by a synod held at Rome in October of the same year. Novatian is said to have suffered martyrdom under the Emperor Valerian I (253-60).
Novatian should not be confused with one Novatus, a priest of Carthage, who advocated re-admitting the "lapsi" without an enforced penance. Cyprian of Carthage came to a position opposed to both and advocated a council be held to establish a policy under which former idolaters could be once again admitted to communion with the church.
Lardner argues that Eusebius and the Greeks in general were correct in calling the Roman presbyter Novatus, not Novatianus. He attributes the origin of the latter name to Cyprian, who called the Roman presbyter Novatianus, as being a follower of his own rebellious priest, Novatus of Carthage.
Novatian believed that the Lapsi should not be let back into the church, Novatian believed that the Lapsi might repent and be put to lifelong penance, but the forgiveness must be left to God, and the Lapsi could not be forgiven on this earth.
Novatian in his writings defends the doctrine of the Trinity, argues that the Old Testament prohibitions on meats must be understood spiritually, condemns Christians who attend public games and praises chastity. Novatian's writings defends the Father as the creator of the world, to combat the teachings of the gnostics, Novatian also defends the unity of the godhead and humanity in Jesus, and wrote about a distinction between the Son and the Father to combat Marcionites, modalists and adoptionists.
Unlike Cyprian, Novatian believed that being inside the church is not a requirement for salvation, but that the church is a congregation of saints, and if sinners would be let inside the church, it would endager the church.
"For Zecharias also tells us, saying: "If ye eat or drink, is it not ye that eat or drink?"--declaring thereby that meat or drink attain not unto God, but unto man: for neither is God fleshly, so as to be pleased with flesh; nor is He careful3 for these pleasures, so as to rejoice in our food. God rejoices in our faith alone, in our innocency alone.-- Novatian, On the Jewish Meats, Chapter V
Novatian's strict views existed before him and may be found in The Shepherd of Hermas. After his death, the Novatianist sect spread rapidly and could be found in every province and were very numerous in some places. Those who allied themselves with his doctrines were called Novatianists, but they called themselves ? ("katharoi") or "Purists" (not to be confused with the later Cathars) to reflect their desire not to be identified with what they considered the lax practices of a corrupted and what was hitherto a universal Church.
While Novatian had refused absolution to the "lapsi" (those who had renounced their Christianity under persecution but later wanted to return to the church), his followers extended the doctrine to include all "mortal sins" (idolatry, murder, and adultery, or fornication). Most of them forbade second marriage. They always had a successor of Novatian at Rome and were everywhere governed by bishops.
Because Novatianists (including Novatian) did not submit to the bishop of Rome, they were labeled by Rome as schismatics. Additionally, Rome also labeled Novatianists heretics for denying that the Church had the power to grant absolution in certain cases (such as to the lapsi).