What is Gnosticism

[Diabolical Materialism]

Can anyone here explain Gnosticism to me? I've read the Wikipedia and am more confused now. I've heard various things described as being "Gnostic" or taking influence from Gnosticism. What the hell is it?

[vitoNova]

Bored old men pulling abstractions and philosophies from their nether-regions because they literally had nothing else better to do. 

[Del Tachi]

The most succinctly I’ve ever heard it described is basically the idea that salvation comes from “gnosis” or knowledge of God as revealed by Jesus Christ.  The knowledge of God revealed by Christ is what saves humanity, not an atoning sacrifice at the cross.  The Gnostic Gospel of Thomas doesn’t even contain a crucifixition narrative, IIRC

In a specific first-century context, Gnosticism was also wrapped up in Hellenistic Paganism - which is where it picked up its connotations of mysticism, orgies and the like. 

[Mopsus]

Its core claim was that the god who created the material world was not Almighty God, but a lesser deity in the celestial hierarchy (an idea it got from Plato). From this it follows that the cosmos was botched from the beginning and the human soul must achieve some sort of enlightenment in order to ascend from the material realm to the eternal. Some gnostics identified the creator of this world (generically called the "demiurge", which is what Plato called him, but different sects had their own names) with Yahweh, from whose harsh rule Jesus was sent to deliver us, thus in their minds resolving the contradiction they saw between the character of Yahweh and the character of the Heavenly Father that Jesus spoke of.

[Filuwaúrdjan]

Heresy.

[Statilius the Epicurean]

Can anyone here explain Gnosticism to me? I've read the Wikipedia and am more confused now. I've heard various things described as being "Gnostic" or taking influence from Gnosticism. What the hell is it?

It's a bit of a confusing term because Gnosticism was never a defined sect but a vague intellectual current in the soup of Platonic, Jewish, Christian, Zoroastrian, Egyptian pagan and possibly Oriental-influenced beliefs that were circulating around the cosmopolitan Roman Empire of the 2nd and 3rd centuries. Broadly speaking it was the idea that the material world is evil and salvation comes from self-knowledge (gnosis) that one's soul is a spark of the divine separate from the body. Although some people like Marcion get lumped in with this movement as "Gnostic" when they didn't have much to do with the above. Really elaborate cosmologies were built out of this stuff that yeah confuse everyone today, incentivised by the doctrine that secret metaphysical knowledge equalled salvation.