Name given to theological doctrines developed and advocated by the second-century Bithynian teacher, Marcion (d. c. 160). He was a Christian by upbringing, but he fell under gnostic influences. In 144 Marcion broke with the Christian church because he could not reconcile the Old and New Testaments. He argued that the God of the OT was a God of legalism and strict justice. In contrast, the God of the NT was a God of grace and love. For Marcion, the OT God who created the world was a lower deity, subordinate to the God revealed in Jesus Christ.
This dualism led Marcion to reject the OT as inspired writing. He acknowledged a severely truncated NT, consisting of the Gospel According to Luke and the ten genuine Pauline epistles all purged of what Marcion regarded as judaizing material. The church declared Marcion's teaching heretical. But the widespread popularity of his teaching forced orthodox Christianity to develop and defend its own list of canonical books. The popularity of Marcionism also prompted Christianity to assert the goodness of creation by the one God of both Testaments.