What on earth is gnosticism?
So, straight up, gnosticism is daughter to spiritual pride, or to put it another way, a son of Satan. Of course, of course, of course, of course, no gnostic will ever put it that way. Has anyone ever come to you and said "I am a proud person?" They will come with feigned humility, "I am an unworthy sinner, but God in his great mercy to a miserable sinner has shown me thus and thus...."
We laugh at the silly tales of early gnosticism. Irenaeus, the second century Christian writer makes an endless list of stupid fables believed by various gnostic sects of his time in his book "Against Heresies". But gnosticism is not merely an ancient error, it's around and alive in the churches today.
Any view which says "I have knowledge which puts me one up on you" is a gnostic error. Any view which says "If you only knew what I knew" is a gnostic heresy.
And there are lots of them around today....
Modern Varieties of Gnosticism
"I have been to Bible College". This view teaches that going to Bible College puts you one up on the poor plebs in the pews who haven't had that privilege. Somehow your greater knowledge makes you more spiritual, a better interpreter, etc.
"I know Hebrew thought." Slightly more subtle is the view in some Christian-Jewish circles that teaches that unless you understand Jewishness, Jewish thought, idiom and tradition, you can't really get into the Old Testament.
"I only use the XYZ translation." Again, more subtle, but all too common. I have secret knowledge which shows me that only my translation is God's Pure Word. Your translation is perverted, and if you only knew the background to your perverted translation (yes they use these extreme words), that I know, you would never open it again, and you would immediately use mine.
"I get messages from God." God leads me by his Spirit in all I do. Talk about one-up-manship! You languish, my friend, in the low-country of Scripture, where you hear God's voice indirectly. I have a hotline to heaven.
"I have been baptised in the Spirit." You are a carnal Christian, having only repented and believed. I have had an experience which takes me far beyond you. (Everyone who repents and believes has the Holy Spirit dwelling inside them - Acts 1:38).
The fundamental error of all forms of gnosticism
The fundamental error of all varieties of gnosticism is sinful spiritual pride. For the Scriptures teach that every believer has been blessed in the heavenly realms with every spiritual blessing in Christ (Eph 1:3). There are no Class B Christians, we are all Class A. You don't need to have any kind of knowledge apart from Christ to be complete in him, and any extraneous knowledge you may have doesn't put you one up on your brother or sister.
Of course no gnostic has ever spoken in such proud terms for Satan is no fool. He hides the hook of gnosticism inside the bait of (sham) humility. Pride has to be unmasked. The apostle Paul had to unmask pride like this:
"Do not let anyone who delights in false humility and the worship of angels (weird ancient gnosticism) disqualify you for the prize. Such a person goes into great detail about what he has seen (read, goes into great detail about what he has read, what she has studied, etc., etc.), and his spiritual mind puffs him up with idle notions." (Colossians 2)
Talk about a balloon popper! This person's mind is not filled with spiritual notions, but idle notions! Some readers of Colossians would have been mad - and so will some readers of this blog. But then comes the coupe de grace, the final chop, the death blow, when Paul says that such a person who thinks he is more in contact with God, is actually disconnected from Jesus!
"He has lost connection with the Head, from whom the whole body supported and held together by its ligaments grows as God causes it to grow." (Colossians 2)
Gnosticism - all forms of it - belongs to the basic principles of this fallen world, and as such we should be done with it.
How to refute gnosticisms
You may think you have to go into great detail and listen to a gnostic's knowledge / dreams/ whatnots in order to examine their case. But this is wholly unnecessary, time consuming and futile.
All you need to establish is this: Do they think thy have privileged knowledge that most people in the church do not have? A knowledge that puts them in a class apart from the church? Above everyone else, privileged? (This form of 'aboveness' may come in many forms, but often it results in separation from others. They won't be able to mix with others, who they now see as beneath them).
Don't worry about the details of the error (historical / visions / translations / etc) - the details are irrelevant.
All you need to tease out is the answer to the forgoing question. Then pray that God will humble them. Don't you humble them, but ask the God who was able to humble a Nebuchadnezzar to bring them to their senses.