Sources: Tertullian, Against Marcion (5 books, ~207 AD); Irenaeus, Against Heresies 1.27; Epiphanius, Panarion 42; Justin Martyr, First Apology 26, 58.

Marcionite Roots (~85 AD) represents the theological tendency that culminated in Marcion of Sinope’s formal movement (~144 AD) — the radical Paulinism that drove a wedge between the Old and New Testaments. The roots lie in the Pauline churches: Paul’s contrast between law and grace, the old covenant and the new, the ministry of death and the ministry of life (2 Cor 3) provided the raw material. The Johannine prologue’s “the Law came through Moses; grace and truth through Jesus Christ” (John 1:17) pushed in the same direction. Marcion did not invent anti-Judaism ex nihilo; he systematized a tendency already present in the Pauline and Johannine traditions. The theological pressure: if the God of Sinai commands genocide (Deut 7), demands blood sacrifice, and punishes sin with death, how is he the Father of Jesus who loves enemies and forgives sinners? Marcion’s answer — they are different gods — is theologically clean but forces the orthodox tradition to work out a coherent theology of the God who is both just and merciful, both creator and redeemer. This is why Irenaeus and Tertullian wrote their longest works against Marcion: his challenge forced the church to think carefully about the relationship between the Testaments, the unity of God, and the nature of canon. Marcion’s canon (edited Luke + 10 Pauline letters) is also the direct provocation for the orthodox canon-formation process.