Gnosticism is a blanket term for various religions and sects most prominent in the first few centuries A.D. Many elements of second-century gnosticsm are pre-Christian. The name of gnosticism comes from the Greek word for knowledge, gnosis (γνῶσις), referring to the idea that there is special, hidden knowledge (esoteric knowledge) that only a few may possess. The occult nature of Gnostic teaching and the fact that much of the evidence for that teaching comes from attacks by orthodox Christians makes it difficult to be precise about the differences between different Gnostic systems. Recently, the word Gnosticism has been used to describe more modern sects which have formed out of the New Age movement and who really do not share the main core idea of Theological dualism.Gnostic beliefs
Gnosticism generally taught that matter was evil and was the creation of a lesser "god", called the Demiurge, after Plato. The Demiurge was the head of the Archons, "petty rulers" and craftsmen of the physical world. But human bodies, although their matter is evil, contained within them a divine spark or pneuma that fell from the good, true God. Knowledge (gnosis) enables the divine spark to return to the true God whence it came.
Many Gnostics (especially the followers of Valentinius) taught that there was the One, the original, unknowable God (the Monad as it is called by Monoimus, or the first Aeon); and then from the One emanated other Aeons, pairs of lesser beings in sequence. (Valentinius listed 30 such pairs.) The Aeons together made up the Pleroma, or fulness, of God. The lowest of these pairs were Sophia ("Wisdom" in Greek) and Christ.
In the Gnostic creation myth, Sophia sought the unknowable One, being so distant from her. In one account, she saw a distant light which was in fact a mirror image, and thus drifted even farther away from the pleroma.
Sophia's fears and anguish of losing her life, just as she lost the light of the One, caused confusion and longing to return to it. Because of these longings the matter (Greek: hyle, ὕλη) and the soul (Greek: psyke, ψυχή) accidentally came into existence through the four classical elements fire, water, earth and air. The creation of the lion-faced Demiurge is also a mistake during this exile, according to some Gnostic sources as a result of Sophia trying to emanate on her own, without her male counterpart. The Demiurge proceeds to create the physical world in which we live, ignorant of Sophia, who nevertheless manage to infuse some spiritual spark into the creation of the Demiurge; that is the pneuma.
After this the savior (Christ) returns and lets her see the light again, bringing her knowledge of the spirit (Greek: pneuma, πνεῦμα). Christ was then sent to earth on the form of the man Jesus to give men the gnosis needed to rescue themselves from the physical world and return to spiritual world.
The three sensations experienced by Sophia creates three types of humans: hylics (bond to the matter, the principle of evil), psychics (bond to the soul and partly saved from evil) and the pneumatics that can return to the pleroma if they achieve gnosis and can behold the world of light. The gnostics regarded themselves as members of this group.
Gnostics identified the Demiurge with the God of the Old Testament; thus they rejected the Old Testament and Judaism, and often celebrated those who were rejected by the Old Testament God. Some Gnostics were believed to identify the Demiurge with Satan, a belief which contributed to the suspicion with which many Christians regarded them.
Soon after the creation of the physical world, Sophia sends a message by way of the Serpent. She gives gnosis to the humans this way, which causes the wrath of the Demiurge, who believe himself to be the sole creator of the universe and the exclusive ruler of this world. The "original sin" thus is in a gnostic context the "original enlightenment", and not an act of sin at all. They also learn that Seth, the third son of Adam, was introduced to the gnostic teachings by both his father and his mother, and that this knowledge has been preserved throughout creation.
It should be noted that the gnostics perceived the Old Testament as myth, and thus subject to interpretation.
Some Gnostic sects were Christians who embraced mystical theories of the true nature of Jesus and/or the Christ which were out of step with the teachings of orthodox Christian faith. For example, Gnostics generally taught docetism, the belief that Jesus did not have a physical body, but rather his apparent physical body was an illusion, and hence his crucifixion was not bodily.
Most Gnostics practiced celibacy and asceticism, on the grounds that the pleasures of the flesh were evil; a few however practiced libertinism, arguing that since the body was evil they should defile it. This led to further distrust, and was an accusation leveled against other groups who did not follow this practice.
(Note: It is a matter of controversy if these sects had a real succession of ideas or communion with each other, of if they more or less coincidentally had the same basic doctrine.)
First, the gnostic sects are often divided into an eastern, or Persian school, and a Syrian-Egyptic school. The Persian school has a more definitive division between light and darkness, whereas the Syrian-Egyptic school is more platonist in character. The latter is the one usually associated with Gnosticism, and the one known to include several Christian elements. A group referred to as the Ophites fall in between both of these strains.
We have two main historical sources for information on Gnosticism: attacks on Gnosticism by orthodox Christians (i.e. Heresiologies such as those written by Tertullian, Hippolytus, Irenaeus and Epiphanius of Salamis), and the original Gnostic works.
Neither of these two sources are entirely satisfactory. Attacks on Gnosticism by orthodox Christians, hostile as they are, most likely suffer from some degree of bias; and orthodox Christians had a tendency to conflate the many differing groups opposing them. There were considerably more Gnostic scriptures written than orthodox Christian ones, which are hinted at throughout the orthodox scriptures.
Many Gnostic scriptures and other works were written, but until the late 19th and the 20th centuries, none of them were available, except in isolated quotations in the writings of their opponents. Many 19th century scholars devoted considerable effort to collecting the scattered references in the works of opponents and reassembling the Gnostic materials.
Several finds of manuscripts have been made since, most importantly the Nag Hammadi codices. But though we now possess a reasonable collection of Gnostic texts, they are still often difficult to interpret, due to the esoteric nature of Gnostic teaching. We are also faced with difficulties in identifying which teachers or sects authored which texts. The Nag Hammadi Library is available in an English translation and is without doubt the most important collection of source texts for research in Gnosticism. With some basic knowledge of Gnostic concepts, it is not too complicated a read.
Origins of Gnosticism
The origins of Gnosticism are a subject of dispute amongst scholars: some think Gnosticism is fundamentally pagan in origin, but has adopted a Christian veneer; others trace its origin to Judaism; yet others think it derives from Jesus, and is a development of his teaching at least as valid as the orthodox one.
It seems clear that Gnosticism, at least in some of its theologically more developed formulations, was heavily influenced by Platonism, Neo-Platonism, Orificism, Stoicism, old Semitic religions, Christianity and (at least in the case of Monoimus) Pythagoreanism.
Note that like everything else about Gnosticism, the identification of a text as Gnostic or not may be controversial, however most Nag Hammadi codices may be assumed to be Gnostic in essence, except for the copy of Plato and the "sayings" Gospel of Thomas.
[Roughly in time order: ]
Gnosticism in modern times
Gnosticism has been treated at length by several modern authors, philosophers and psychologists: