Historically speaking, ‘heterodox Christianity’ should be understood to refer to all those forms and traditions that had been part of emerging Christianity, but which were eventually marginalised or suppressed in the process of ‘making’ mainstream Christianity. Although this category would, strictly speaking, include Jewish-Christianity, in this context we refer to those traditions that were identified to be sectarian or gnostic.

Most of the knowledge of Christian Gnosticism derives from texts from the Nag Hammadi library of the fourth century CE. By comparing these texts with citations and references in early Church Fathers such as Irenaeus, Hippolytus or Ephiphanius, one can connect these texts loosely with some or other trajectory or tradition in the emerging gnostic movement. Gnosticism itself was not a monolithic movement. Although most gnostic texts show evidence of some significant connection with Jewish thinking (in worldview, cosmology, demonology or mythology) some streams are more Jewish than others. Sethian Gnosticism (so called because of the prevalence of traditions relating to the mythological figure of Seth) was more Jewish in character, while Valentinian Gnosticism (named after the great gnostic teacher Valentinus) was more neoplatonic, thus more philosophical, in orientation. The discussion here will focus on two second-century CE Valentinian gnostic works.