Gnosticism

Everyone knows that an agnostic is someone who does not believe in God. But, actually that's not quite right. Agnosticism is really just the belief that it is not possible to know whether or not God exists. So, it is even reasonable for a Christian to be agnostic. Such a person would say, “I can't know that God exists; that's what I have faith for!”
But few people know what a gnostic is (no “a”). Gnosticism actually dates back to before Christ. But the first Christians, or at least some of them, considered themselves gnostics.
Gnosticism is not a religion. It is merely a way of thinking about religion and life and anything for that matter. A gnostic views all knowledge as coming from a single source. This does not contradict the Christian view that all things are created by the One God. It is just a different way of viewing the same thing. But, perhaps an important difference.
The gnostic Christians were actively suppressed very early after the birth of Christianity. Many of their doctrines were seen to contradict the teachings of Christ, which is rather strange since a true gnostic would never subscribe to any one doctrine. So accusing them of contradicting Christian doctrine would be like accusing someone of not liking vegetables just because they like meat.
But to the early Christian church, anyone who did not believe exactly what they believed were considered heretics. (This is proven over and over throughout Christian history and accounts for so many “denominations” and divisions of the Christian religion today.) To this day, the very hallmark of Christianity, is the insistance that you either believe what we believe, or you are wrong. In other words, Christian's by their nature (the nature of Christianity) believe they are “right”, and everyone else is “wrong”, even when only a very few of them think they are “right” (i.e. Christian cults).
But the gnostic Christians were not like that. They believed that all knowledge (and hense, all beliefs) led ultimately to the source of Knowledge, that being of course, God. So there were as many different paths to knowing God as there are different things to know. But they emphasized being able to know the difference between true knowledge (or just “knowledge”) and false knowledge (or, more correctly, “deception”).
To a gnostic, deception is “the devil”, in the same sense that knowledge is “God”. Deception is the source of all “evil” and “suffering” in the world. The “devil” is not a magical creature that lives beneath the earth (or in some other reality, as Christians believe today) but he is a very real and present phenomenon of intellectual action that we must resist not in fantasy, but in reality.
Learning to recognize and resist the “devil” is the obligation of every servant of God. And we do so by seeking true knowledge, which allows us to discern deception. The only weapon against deception is truth. But truth can only be properly wielded against deception (evil) by those who have the necessary qualities of a “true believer”.
Those qualities are outlined in the Bible (and numerous other books for that matter), so I won't go into them here. But I should point out that merely pretending to have these qualities does not qualify you to do battle with evil. The qualities I speak of can only be granted by God himself, no man can obtain them according to his own desire or will (which the Bible also clearly says in many places and many ways in order to be clear on this point). And hense, no man can come to know the source of all knowledge unless they have indeed been chosen by God.
The popular Christian belief that we have so-called “free will” (or the oximoronic “limited free will”) and that life is some sort of test to see who deserves to live forever, is a spiritually childish notion to a true gnostic.
Even though gnosticism was suppressed and literally outlawed by the church, it has quietly survived all these years. To a gnostic this is no surprize. They know that the truth (i.e. source of knowledge, a.k.a. “God”) is the living and conscious force behind all of nature. So gnosticism cannot be destroy like some belief system or religion. Even if all men were destroyed, and a completely new intelligent species envolved, there would still be gnostics, even in the new species.
But, of course, gnosticism is just a word. You don't need to know the word to be a gnostic. I call myself a gnostic only very hesitantly after studying the history of gnosticism and learning that its principles are precisely my own. I did not adopt gnosticism, it adopted me.

P.S. It is difficult, if not impossible, to ever completely, or even correctly, define gnosticism in terms of human language. Like I have said, it is not a religion, not even “pure religion”, it is only a way of seeing things that allows one to “see” the religious paths, but it is not a “path” itself. It is like Ti-chi, in the sense that Ti-chi too, when correctly practiced, is a “way of seeing”. You could say that gnosticism is a kind of intellectual Ti-chi. Except, unlike Ti-chi, gnosticism can not be taught person-to-person. It can only be learned God-to-person.