Gnosticism was a religious movement older than Christianity. There were both types of Christian and non-Christian Gnosticism because there was syncretism, or mixing. They believed that humans were trapped in their bodies and in this evil material world that was created by a cosmic disaster, by a malevolent deity who was not Christ. Christian Gnostics believed that Christ was one of the aeons or divine beings from the Pleroma, the Divine Realm, as described in the Apocryphon of John, part of the Nag Hammadi Library of Gnostic literature. Salvation was by esoteric knowledge, although ultimately self-knowledge. Gnostics believed in the dualism of the good spirit and evil matter. The material world was an evil place from where Gnostics had to escape. They believed that not all humans had the Divine Spark. The aeons emanated from the Ultimate God, the Monad in the Pleroma. The origins of Gnosticism are unclear today, but probably it came from Persia or further east. It had a lot of Greek influences. Today, after the discovery of the Nag Hammadi Library as leather-bound papyrus codices in a sealed jar in Egypt, in 1945, some people are trying to revive Gnosticism. "Gnōsis" is Greek for knowledge.
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