But all those Christians who later apostasize think they know that they have faith when in fact they do not really know that they have faith. So how do you know you are not one of those people who thinks he knows that he has faith when in fact he does not really know that he has faith? In other words, how do you know that you are not an apostate-to-be? (Appealing to the 'assurance verses' here would simply beg the question, because it would assume precisely what you are trying to prove, namely, that the 'assurance verses' apply to you.)
-A8
Well, I suppose this question boils down to how I would distinguish myself from the next guy who might have the same knowledge I do and says the same things I say, but then he falls away permanently. I do not think it is possible to "prove" that difference to you or anyone else. Only God and I know what my faith truly is. So, I can report to you things like I know that God has actively worked in my life since my conversion, and that those workings directly match what is foretold in the Bible for all Christians, but you can't "know" it the way I "know" it. The same is true in reverse.
We can only know for sure what is in our own hearts. I personally have never known someone who "convinced" me he was a Christian and then later fell away permanently. That is not at all to say that very convincing people have never fallen away, of course that has happened, but I can't compare what the heart of a false believer looks like (from the outside) to my own through my experience.
From a practical standpoint, how does it benefit me as a Christian to disregard how the assurance and perseverance verses speak personally to me? One possibility would be if they "moved" me to sloth, but they do not because I am well aware of the multitudes of other verses that cover the subject. So, if my "objective" and honest reading of those verses is the Reformed view, then why should I reject that? They bolster my faith and thanksgiving to God.
Now, if it turns out that I really am a pretender, then by my own beliefs there is still nothing I could ever do to change that. God would have been using me in my pretender role all along for His purposes. Glory be to God for that if it was true. This is partly why I can have assurance. WHATEVER the truth is, it's all in God's hands, not mine. Therefore, I will spend my life living with assurance in Christ and His promises, as I understand them, and not worry about whether I am a pretender. Either way, it will be to God's glory, and that is all I could ever truly want.