Gnosticism is a belief that the universe is a duality: light and dark; good and evil; flesh and spirit, etc.. Gnosticism hit its peak in 150ad. Some of the New Testament books confront Gnostic beliefs, like 1 John.
Outside of Christian Science and other odd duck cultish religions, gnosticism seems to have fallen away. A belief that matter is evil and spirit is good is probably not a threat anymore. Or is it?
It might be if you attend an Evangelical church in America. Gnosticism has carried over in our belief concerning the Gospel and its effects in the believer. Modern Christian Gnosticism goes like this:
“I believe that Jesus died for my sins. God has put me right with God. He has given me a new spirit and spiritually speaking I’m good to go. Therefore, since He’s made me spiritually good with God what I do in the flesh doesn’t matter. Flesh is all evil, always will be, you can’t expect anything good there. So I stand in security in the spirit and let my flesh continue in sin and grossness. Mind over matter, baby! I don’t mind sin, so it doesn’t matter because it’s just the flesh, what else do you expect?”
That is nothing more than gnosticism. When the NT speaks of flesh and spirit you must make sure you know what is being talked about, usually determined by context.
The “flesh” does not always mean our bodies, it is indeed possible for the believer to mortify the deeds of the body and to use the body to be a vessel fit for the Master’s use. Your old man (your sin nature, also sometimes referred to as “flesh”) is always corrupt, but has also been put to death with Christ.
Since the old man, the flesh nature, is put to death, we are to reckon ourselves (our life we still have in our flesh and bones body) alive to Christ. “I am crucified with Christ, nevertheless, the life that I know live in the flesh (my body, not my old nature) I live by the faith of the Son of God.”
Make sure you know your terms and beware of the subtle trap of gnosticism that keeps believers defeated in sin, yet feeling really good about it.