A modern definition of Gnosticism is "a prominent heretical movement of the 2nd-century Christian Church, partly of pre-Christian origin. Gnostic doctrine taught that the world was created and ruled by a lesser divinity, the demiurge, and that Christ was an emissary of the remote supreme divine being, esoteric knowledge (gnosis) of whom enabled the redemption of the human spirit."
But we know that the modern definition Religion has changed so I imagine that all that was labeled Gnostic was not the same. The truth is that Gnosticism has resulted in numerous debates and countless interpretation for 2000 years. The complex nature of Gnostic teachings are not only complex but often cryptic, even secretive.
Couple that with the fact that much of what we know about Gnosticism has commonly come from critiques. so the question inevitably remains what was the early sectarian gnostic systems all about.
In the "Adversus Haereses" by Irenaeus we hear that there were different sects of philosophy in the 2nd-century disparaging and even ridiculing gnosticism. Scholars have had to depend heavily on heresiologists and their hierarchical prejudices because of a lack of alternative sources.
Finding manuscripts near Nag Hammadi in 1945, however, gave us a cache of 4th-century Gnostic writing that allowed another round of debates and interpretation filtered through the prejudices both pros and cons of our modern view of ancient religions.
The texts would be translated of from the ancient Coptic language into English in 1977 did not relieve the difficulties.
One way to promote ones own view is to accuse others of something that is generally not understood but is accepted off hand as incorrect. In doing away with the dualist Marcion it was common to label him a Gnostic. We see the same practice with the Founding Fathers who are often accused of being Deists.
Gnostics did not call themselves Gnostics but appear to have been around long before Jesus and were probably unrelated to Christianity.
- Some interpret that they thought the "material world is bad and that the spiritual realm was good."
- Jesus said his kingdom was not of this world but of course the word world did not mean the material world as much as the organized political world of Pontius Pilate.
- We see in John 6:63 "It is the spirit that quickeneth; the flesh profiteth nothing: the words that I speak unto you, [they] are spirit, and [they] are life."
- In 2 Corinthians 3:6 we see "Who also hath made us able ministers of the new testament; not of the letter, but of the spirit: for the letter killeth, but the spirit giveth life."
- We can see this same emphases and superiority of Spirit over the material flesh in Romans 8:2 "For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death."
- Romans 8:10, "And if Christ be in you, the body is dead because of sin; but the Spirit is life because of righteousness."
- Which is repeated in Galatians 6:8, "For he that soweth to his flesh shall of the flesh reap corruption; but he that soweth to the Spirit shall of the Spirit reap life everlasting."
- People suggest that they considered the material world is under the control of evil.
- A "divine spark" is within some which provides redemption.
- Matthew 16:17, "And Jesus answered and said unto him, Blessed art thou, Simon Barjona: for flesh and blood hath not revealed [it] unto thee, but my Father which is in heaven."
- John 1:13, "Which were born, not of blood, nor of the will of the flesh, nor of the will of man, but of God."
- Salvation is through some sort of secret knowledge.
- God could not have created evil, which is the result of an inferior, blind, evil "god" or Archons who pretends to be God.
- If the "divine spark" is awakened we will be drawn toward the Pleroma or divine realm where God intended us to be.
Some think none of these ideas are either in the Old Testament or apostolic text which is why they were supposedly rejected by early Christians.