Marcion, son of a Christian bishop in Asia, was one of the early architects of the belief in Gnosticism that there were two gods. He was born in about A.D. 85, which means that not all of Jesus' apostles had yet died. Because of his merchant activities, Marcion amassed a fortune. Unfortunately, either due to misunderstanding or youthful indiscretion, he was accused of defiling a virgin. He left his home in Sinope, Asia Minor, in shame, excommunicated from that church. Marcion went to Rome and offered the conservative Roman church a gift of 200,000 sesterces. Perhaps it helped smooth his initial acceptance into that church, but once the patristic fathers understood how divergent Marcion's views were to their orthodox Christian beliefs, they gave back the money, branded him a heretic, and expelled him from the mother church in Rome in A.D. 144. Marcion then embarked upon a mission to establish his own churches in Rome, Carthage, Syria, Nicomedia, Smyrna, Phrygia, Antioch, and elsewhere.

Marcionites embraced the idea of an eternal struggle between good and evil. They rejected the God of the Hebrew scriptures as being the Father of Jesus. One of Marcion's followers named Apelles called the god of the Hebrew scriptures an angel of evil (arch enemy of Good) while another of his students asserted instead that “eternal matter” was the root of evil. Of major importance, however, is the Marcionite belief that Jesus brought secret knowledge that he did not share with the masses but rather taught to a select group of chosen ones. Marcion, in compiling his own canon of acceptable sacred texts, completely eliminated the old Hebrew scriptures from his canon. This set him apart from the orthodox Christians who relied on the Hebrew scriptures and regarded Old Testament prophecy as fulfilled in the life and ministry of Jesus.

Marcionites wanted nothing to do with Jewish practice, belief, or influence. Toward that aim, Marcion excised all positive references to the Jews in the letters of Paul and the Gospel of Luke, retaining and using his heavily redacted version in his teachings. Marcionites believed that the Demiurge was an inferior god, the cruel God of the Jews and the Hebrew scriptures who made women suffer in childbirth. The Father God who created Jesus, however, was a god of grace, love, goodness, and forgiveness.

Another important Marcionian idea refuted by the orthodoxy was that Christ appeared to be human but, in reality, was not. Thus, no Resurrection of the Flesh, Second Coming, or Judgment Day could be considered plausible. Finally, Marcionites shunned marriage, engaged in fasting, and observed strict asceticism.