Gnosticism (from Ancient Greek: γνωστικός, romanized: gnōstikós, Koine Greek: [ɣnostiˈkos], having knowledge) is a collection of religious ideas and systems which coalesced in the late 1st century AD among Jewish and early Christian sects.
As we can see Gnosticism really means having knowledge.
Many Christians today are focused on knowing the right doctrine as if salvation was about having the right knowledge in your head.
Salvation is by faith alone in Christ alone by grace alone.
We are not eternally saved by having the right doctrine.
Why is this so important. Because your christian faith can turn into Gnosticism.
Where you measure yourself against other Christians based on if you have the right beliefs, know certain doctrines etc. Those who have other doctrines are then called heretics and banned or blocked or exposed.
Gnosticism is about having the right knowledge. Christianity is about faith in Christ.
Its between you and God and Christ is the mediator. Its not between you and doctrine and you being a priest over other believers who don't have according to you the right doctrine or who do have the right doctrine.
How do we recognize Gnosticism?
Gnostic ideas can be that Jesus Christ was just a man and then when he got baptized by John in Jordan he became a representative of the Christ principle.
Gnosticism could be that Paul was a Gnostic and that people who look upon the Pauline epistles as more important than the rest of the bible are Gnostics.
Gnosticism could be references to the Nag Hammadi library.
Gnosticism could be talk about the demiurge.
How do we defend ourselves from Gnostic teachings and Gnostics. We stick to the king james bible.
But remember when people start to promote having the right knowledge within the king james bible movement as a sign of that you are on the right way and not an heretic, watch out because we don't stand by knowledge, we stand by faith and by grace.
(Romans 5:1-5 [KJV])  Therefore being justified by faith, we have peace with God through our Lord Jesus Christ:  By whom also we have access by faith into this grace wherein we stand, and rejoice in hope of the glory of God.  And not only so, but we glory in tribulations also: knowing that tribulation worketh patience;  And patience, experience; and experience, hope:  And hope maketh not ashamed; because the love of God is shed abroad in our hearts by the Holy Ghost which is given unto us.
(II Corinthians 5:7 [KJV]) (For we walk by faith, not by sight:)
Its all by faith and by grace.
No point arguing doctrine.
- Gnosticism From Wikipedia, the free encyclopedia, https://en.wikipedia.org/wiki/Gnosticism