Marcionism was a religious movement based on the teachings of the 2nd-century heretic Marcion of Sinope. While none of Marcion’s writings have survived to the present, his teachings are known through several early Christian writers including Justin Martyr (AD 100–165), Irenaeus of Lyons (AD 130–200) and Hippolytus (AD 170–235). These men combatted Marcion in defense of the truth.