Among all the Christian, Biblical, literary, historical, mythological, and other themes associated with Lost, I rarely hear anyone making the Gnostic connection.
To simplify: the Gnostics were a branch of early Christianity more concerned with the divine/god aspect than with the idea of Christ-as-man. The word "gnosis" literally means "knowing," which directly contradicted the core Christian tenet of "believing." The Gnostics searched for a way to know god, not just believe in god. They were of course defeated by the Christians, and most of their history was lost, but in 1945 they discovered a lost Gnostic gospel in Nag Hammadi, Egypt, which gave us a new insight into their understanding of the universe.
So then a friend of mine offered a theory after last week's amazing episode "Ab Aeterno." He said (and this is just a THEORY) that "Jacob and MiB are the same person."
I could get into more about why that theory applies, but I want to connect it specifically to Gnosticism. The basic Gnostic myth is that before time began there was one single divinity, but this divinity was inert, not moving, not doing anything, because it was already one and all. So in order to create time, space, and inertia, the divinity needed to split in two, in a sense "give birth" to "twins."
But unfortunately what happened was the second twin pushed ahead and was born first, and was therefore incomplete and corrupt. This twin (let's call him the "bad twin," natch) created the universe, but fell under the illusion that he was the only god. He denied that he had a twin, and so pushed forward on his own, doing his own thing, thinking that his universe was everything and that he was the only divinity.
So the Gnostic myth is basically that all time, space, and creation is the result of the actions of the "bad twin," and that the purpose of the universe is to eventually reunite with the "good twin" and rejoin the perfect wholeness of single divinity. In fact, they believe the human condition is one of falling from grace, falling away from the true divinity under the spell of a corrupt god, and that a human's purpose is to see through the corruption and darkness and come to know the true divinity, to attain gnosis.
In Lost they've hinted that the real world "doesn't matter" or "isn't real." With the characters, they've created a space in which these people can redeem themselves from their darker past and seek a purer truth. Every character in Lost at some point goes through a process of seeing through lies and illusions to find a greater meaning and learn something about themselves.
So Jacob and MiB, as suggested in last week's episode, may very well be two halves of the same whole. Their purpose is to simply exist and be diametrically opposed to one another as a means of passing time. They both have a goal: Jacob's is to guard the prison, and MiB's is to escape it. Whether or not Jacob "proves his point," this is what the two of them are made to do.
They cannot interfere with the real world, and can only manipulate those who come on the island, so the metaphor here is one of overcoming the corruption, evil, and malevolence, and finally joining together the darkness and light in a perfect union. Humanity's role in this process is exactly the same: to overcome their own darkness, seek the light, and in the end create a perfect union of the two which leads to a knowing of the truth, not just a believing of it. The Gnostic goal is to literally go through the experience, walk through the darkness, because it's the only way to truly know the light when you find it again. In Lost, many of our characters learn something by having an amazing or terrifying experience, not just getting the answers handed to them.
Regardless of whether this Gnostic analogy fits, Lost is a show that transcends every religion and mythology and will ultimately establish its own mythos that both stands apart from the others, and yet is connected to all of them.