The term “Gnosticism” was first coined in the 17th century to refer to an early Christian described by the Church Father Irenaeus of Lyon in his five volumes Against Heresies (ca. 185). Historians of religions use the term to refer to a religion that probably developed around the turn of the era from Jewish roots and took on various forms—Jewish, Christian, and others. In this religion, gnosis (“knowledge”) is the prerequisite to salvation, and consists of revelations concerning the true nature of God and the human self.

The traditional God is split between a transcendent deity and a lower deity responsible for the creation of the material world. The true human being (soul or spirit) is regarded as a divine spark that originated in the divine world and is now imprisoned in a material body. Salvation consists of an escape from the cosmic prison and a return to the soul’s divine origin. All of this is given expression in an elaborate mythology.

In Christian forms of Gnosticism, Jesus Christ is the heaven-sent revealer of gnosis. Early of this religion referred to themselves as gnostikoi, “Gnostics,” that is, those in possession of saving gnosis. The sources for our knowledge of ancient consist of and refutations by Christian fathers, especially Justin Martyr, Irenaeus, Hippolytus, Tertullian, Clement of Alexandria, Origen, and Epiphanius. Thanks to manuscript discoveries, we now have primary sources available in Coptic versions found in the Nag Hammadi , the Berlin Gnostic Codex, the Bruce Codex, and the Askew Codex.

The religion of the Mandaeans (Gnostics) of Iraq and Iran is the only surviving remnant of the ancient Gnostic religion. was especially prominent in Egypt, first in Alexandria and then spreading into the (Hinterland, not Alexandria). Indeed, the first Christian teachers in known to us by name were Gnostic “heretics” active in Alexandria in the early second century: Basilides and his son Isidore, Carpocrates and his son Epiphanes, and Valentinus, who moved to Rome ca. 140.

While several forms of Christian existed in Egypt, two were especially prominent, as reflected in our primary sources: “Sethian” or “classic” Gnosticism, in which the heavenly Seth plays an important role as revealer of gnosis and spiritual progenitor of the Gnostic “race”; and Valentinian Gnosticism, which originated as a more specifically Christian adaptation of classic and is reflected in the writings of Valentinus and several prominent pupils of his, such as Ptolemy, Heracleon, , and several others.

Heracleon and were probably active in Alexandria in the mid-second century. Valentinian Christianity spread to all parts of the Empire and beyond, and persisted in some areas into the seventh century.

The first Christian teacher in Alexandria to label Christian Gnostic teachings as a deviant “heresy” was Clement of Alexandria, who taught in the last quarter of the second century. His writings reflect the influence of Irenaeus’ treatise Against Heresies. Ecclesiastical opposition to Gnostic teachings seems to have been sponsored by Bishop Demetrius of Alexandria (189-232).

The official position of the Alexandrian Patriarchate on Gnostic and other “heresies” was adumbrated by St. Athanasius in his paschal letter of 367, in which he proscribed heretical and “apocryphal” writings and established the contours of the biblical canon of scripture. Even so, Gnostics could be found in for some time after that. Around 600, John of Paralos wrote a polemical treatise against and other heresies.

A special form of the Gnostic religion, Manichaeism, founded by the prophet Mani (216-277), was brought by of Mani to from Mesopotamia around 270. Several Manichaean writings exist in Coptic versions preserved in fourth- and fifth-century manuscripts found in the 20th century. The first Egyptian Christian refutation of Manichaeism was penned by Theonas of Alexandria (282-300), but Manichaeism persisted in for several centuries.