Marcionism is a heresy that is attributed to an early church figure by the name of Marcion of Sinope. Marcion was the son of a bishop and moved to Rome about 135 AD. Marcion, who was denounced by the early church fathers including Justin, Irenaeus, Clement of Alexandria, Origen, and Tertullian in the second century, taught a dualistic belief in a distinction between the God of the Old Testament (demiurge) and the God of the New Testament.