Novatianism
The Novatianists following Novatus, or Novatian, 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. They were declared heretical.
Novatian
Novatian was a Roman priest who in 251 opposed the election of Pope Cornelius, following the assassination of Pope Fabian during the persecution, on the grounds that he was too lax in accepting the lapsed Christians. He let himself be made a rival pope, one of the first antipopes. He held that lapsed Christians, who had not maintained their confession of faith under persecution, may not be received again into communion with the church, and that second marriages are unlawful. 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 (253-260).
Novatianism after Novatian
After his death, the Novatianist sect spread rapidly, were found in every province, and in some places were very numerous. Those who allied themselves with the doctrines of Novatian were called Novatianists; their own name for themselves was the καθαροι ("katharoi"), or Puritans, reflecting their claim not to be participants in the lax practices of the Catholics by which they believed the Catholic Church to have been corrupted. They went so far as to rebaptize their converts. Novationists (including Novatian) were labelled by Rome as schismatics in not submitting to the bishop of Rome, and were by Rome labelled heretics in denying that the Church has the power to grant absolution in certain cases (such as to the Lapsi)[who?]. Beyond that, their practices were the same as that of the Catholic Church in almost everything, including monasticism in the fourth century.
In the 4th and 5th centuries, the Donatists of North Africa followed a similar belief about Christians who had lapsed under the pressures of persecution. They too were declared to be heretics.