The Christian theologian and leader Marcion (active mid-2nd century) promulgated views that were condemned as heterodoxy.
Marcion came from the Black Sea seaport town of Sinope on what is now the northern shore of Turkey. According to the writer Hippolytus, his father was the bishop of Sinope, so Marcion may well have been raised as a Christian. Once grown, Marcion entered the ministry and, toward the middle of the 2nd century, moved to Rome. There he gathered followers and in time began publically promulgating his theological views to the Roman Church at large. To his surprise, these views were not received sympathetically, and at the first known Roman synod, Marcion was excommunicated (144). Subsequently he became the founder of the rival Marcionite Church, which, in its ecclesiastical life, liturgy, and sacraments, paralleled the Christian Church. Marcion's rival church grew with considerable success, and Marcionite communities were found throughout the Mediterranean area well into the 4th century.
That the Marcionite Church, and more particularly, its heterodox doctrines, posed a threat to the early Christian Church is well attested to by the number of, as well as the vehemence of, treatises written against it in the 2nd and 3rd centuries. The longest and most important of these is by Tertullian. In spite of his severe opposition to Marcion's doctrinal views, that Tertullian could at the same time commend Marcion and his numerous followers for the purity and austerity of their moral life probably gives lie to the story, circulated later (4th century) by Epiphanius, that Marcion was forced to leave Sinope for Rome because he had been caught in an act of gross sexual immorality and excommunicated by his father.
The view for which Marcion was most soundly criticized was not only that he denied any connection between the Old and New Testaments but that he also rejected the Old Testament in its entirety. The God of the Old Testament, his studies led him to assert, was a God of Law and Judgment, completely different from the God of Love and Mercy, the Father of Jesus Christ, as revealed in the New Testament. The former, "Creator God," held mankind in a deceitful grasp from which the "Redeemer God" sought, through the mission of Jesus, to save him.
These views, expounded in Marcion's "Antitheses," led the Marcionite Church to develop its own canon of Scripture, a fact that played no small part in forcing the Christian Church to regularize its own canon. The Marcionite "Bible" consisted of major portions of the Pauline Epistles (especially where law and spirit were opposed) and an expurgated version of the Gospel of Luke in which the passion and death of Jesus appear as the vengeful work of the Old Testament God.
Further Reading on Marcion
The best study of Marcion is in German. Of great value in English is Edwin Cyril Blackman, Marcion and His Influence (1948).