How does one become an un-Christian?

In my previous life as an Arminian Christian, and now as a somewhat Emergent one, I am still confronted with the same question: How could I fall from grace?

First, a definition of Arminian, in case you thought I meant Armenian. Arminianism was first propounded by a Dutch theologian named Jacob Arminius (1560-1609). He broke with the Calvinistic thought of his day in a number of respects, one being "perseverance"; i.e., that those who are believers in Christ will persevere in their faith until the end. Arminius taught that a believer could, in fact, lapse into apostasy, from which s/he could not be restored.

Arminianism, in a slightly altered form, was taught by the great John Wesley. He differed from Arminius in this important respect, however: he believed that one could be restored to faith after apostasy. That invaluable resource Wikipedia provides the following explanation:

Wesley fully accepted the Arminian view that genuine Christians could apostatize and lose their salvation, as his famous sermon "A Call to Backsliders" clearly demonstrates. Harper summarizes as follows: "the act of committing sin is not in itself ground for the loss of salvation...the loss of salvation is much more related to experiences that are profound and prolonged. Wesley sees two primary pathways that could result in a permanent fall from grace: unconfessed sin and the actual expression of apostasy." Wesley disagrees with Arminius, however, in maintaining that such apostasy was not final. When talking about those who have made "shipwreck" of their faith (1 Tim 1:19), Wesley claims that "not one, or a hundred only, but I am persuaded, several thousands...innumerable are the instances...of those who had fallen but now stand upright."

The difference between the Wesleyan view and the newer Emergent view is that Wesley was talking about professed Christians only. The Emergent view is that membership in the Kingdom of God is inherited by all of God's creatures (the human ones, that is) at birth. We have to go further than to say that a person who knowingly accepted Christ could knowingly give him up.

What giving up Christ's free gift of salvation means for those who have never heard of Christ is a different question altogether. But the answer escapes me as I write this. I'll try to figure it out in my usual "theology from the ground up" way. No successful results are guaranteed :).