For by grace you have been saved through faith. And this is not your own doing; it is the gift of God, not a result of works, so that no one may boast. --Ephesians 2:8-9Often, we (Calvinists) tend to use the use of the word "work" here to support our conception of "grace alone," charging Arminians with making salvation based on works. While I think this is a supportable position, it will be easier to shift the focus a bit.
Why "not a result of works"? The text answers, "so that no one may boast." Thus, "works" covers all those things that would allow us to boast. I take boast here to mean "boast in or of themselves," since Paul elsewhere speaks of boasting in Christ. So, then, what would allow us to boast in or of ourselves? If we are all at the same level in and of ourselves, then we cannot look at another and call ourselves better, thus, we would not in that case be able to boast in or of ourselves. At the same time, if we were in an identical condition, then there would be no reason to call any particularly "saved." Thus, in order that we not be able to boast in or of ourselves, and for some to be saved, those who are saved must not be saved on account of any way in which that they, in or of themselves, are different from others.
Now, on the Arminian view, so far as I understand it, the grace by which we are saved is a grace which makes it possible that any individual have the possibility of salvation, and not a grace which accomplishes anyone's salvation for them. This view of grace would place all people at the same level to begin with, supposing free will to make the difference between one individual who is saved and another who is not saved. Yet, in that case, either such an act of free will does not differentiate one person from another, or is not done in or of that person's self who is freely willing to do such a thing, or, which seems contrary to the verses at hand, one's free choice to believe does differentiate one from others in or of oneself, and thus one's salvation is a cause of boasting. Yet the first two seem contrary to the purpose of free will, for it is by those that free will is supposed to allow for personal responsibility.
Now, one might argue that, if the Arminian view of grace is right, then, since only that grace actually given to us must be impossible to boast of, we must only be unable to boast of receiving that grace which opens a door to salvation. Yet, verse 5 "even when we were dead in our trespasses, made us alive together with Christ—by grace you have been saved," this salvation by grace is spoken of as a making us alive together with Christ when we were dead in our trespasses, and, further, it is said, verse 6, "and raised us up with him and seated us with him in the heavenly places in Christ Jesus," which is the hope of eternal life, and verse 7, giving the point of this salvation, says, "so that in the coming ages he might show the immeasurable riches of his grace in kindness toward us in Christ Jesus." Now, if all this may be said of each and every individual, then I am lost as to how we are to keep from a doctrine which says that all shall be saved unto eternal life, and hell empty, both of which are contrary to scripture.