Were they never saved in the first place?

I brief exchange I had with a Roman Catholic on YouTube:

"But the Calvinist position on eternal security requires not just that this 'possibly' be the case. It requires that this ALWAYS be the case in such situations as when a person no longer fulfills the conditions by which a Calvinist regards another person to be regenerate and justified."

To some degree you and I are arguing at cross-purposes because we're making different points. There are critics of Calvinism who act as though the very idea that an apostate wasn't saved in the first place is a rationalization you'd only resort to if you have a fanatical precommitment to Calvinism. I'm making the point that as a matter of principle, that's not an artificial position or stopgap. Now, your objection isn't to the principle but to universalizing the principle. 

"My point was less that I think a No True Scotsman Fallacy is going on - if eternal security is true, then texts like 1 Cor. 10 HAVE to be read as if loss of salvation is impossible. My stance is that the bulk of such texts are reduced to nonsense if this effort is attempted. It is not so much the issue that I think a fallacy is being committed. I think that Calvinists are pre-committed to missing out on certain paradigms. Looking at a typological argument in such a way that you keep pointing out that not all the Israelites were saved might be how to salvage that text within the Reformed perspective, but it's just *not* the right methodology for exegeting the text in its own context. The text must be exegeted rightly within its own context alongside its compatibility and being rightly informed by and informing other texts. I do not believe that the Calvinist effort succeeds in this."

As far as that goes, I think 1 Cor 10:1-4 is counterproductive to Catholicism. Why does Paul draw a parallel between the experience of the Exodus generation and baptism/communion? Why does he say most members of the Exodus generation perished despite having an analogous experience? 

The only explanation I can see is that some Corinthians were treating baptism and communion as talismans that would protect them from certain kinds of harm. That false confidence made them indulge in risky behavior. Paul is warning against that brazen, superstitious mentality. Otherwise, I don't know the purpose of Paul's comparison. 

"Even if a Calvinist knows zero, zip, zilch about a person prior to the present moment, if the indications given in the present moment are that said person doesn't meet the 'salvation' criteria, then the Calvinist is *dogmatically* required to believe the person never met said criteria, even if the person believed that he did, and even if on the surface the person appeared to meet those criteria previously."

That's an issue of theological method. How do we deal with points of tension in Scripture? Can someone who's elect, regenerated, justified lose their salvation? If so, does that mean they lost their election, justification, and regeneration? If so, is there something they can do to regain their election, regeneration, justification? How you answer one question raises additional questions. There are different potential responses:

i) The Bible is contradictory. It contains divergent theological paradigms.

ii) It's all true but paradoxical and we have no way to resolve the tensions, so we must leave them as is.

iii) Harmonize the tensions. If so, in what direction? Do we harmonize "eternal security" passages in light of apostasy passages or vice versa? 

iv) This isn't just an issue in Calvinism. Take the role of election in Thomism and Augustinianism. Surely it's nonsensical to say that someone God eternally elected can end up in hell. 

v) Traditional Catholicism also makes categorical claims about humans without knowing anything about any human in particular. Take the doctrine that no one is sinless (except for Jesus and Mary). The doctrine that grace is a necessary preliminary (pace Pelagianism). 

"I am not so willing to think, as the nonbelievers do, that the faith of so many if it *seems* to come from social conditioning is ultimately a bit more superficial of a faith. Nonbelievers make this argument in order to try to and impress upon people that their religious beliefs are not particularly special and are just absorbed by them because of the peer group and/or culture into which they are born - the old "if you were born in India, you'd be a Hindu" argument. Don't you think that, by employing this sort of approach, you are going a little too far?"

I'm not claiming there's a universal correlation. But there's more than enough to establish my point that in principle, someone can believe in Christianity even though he hasn't experienced saving grace. As such, if he ceases to believe, he was never saved to begin with. 

"Sociologically, we believe a LOT of what we believe because Mommy and Daddy do. We don't even have to necessarily talk about peer group because I think familial belief is more fundamental - my impression, at least, is that one's peers have less to do with one's views on politics, morals, religious beliefs, etc., than one's parents. Most Protestants who profess, say, Sola Fide do so because it was taught to them by Mommy and Daddy and the church that Mommy and Daddy took them to and modeled listening to. Even so, I don't believe that the question before us is reducible to a sociological calculation. People convert. People choose to 'own' their religious beliefs after serious reflection, certain experiences, etc."

i) No doubt God uses social conditioning to foster Christian faith. But in the case of "true believers," that must be undergirded by saving grace.

ii) In addition, the exceptions are striking. On the one hand, people from non-Christian backgrounds who convert to Christianity. On the other hand, people from a Christian background who resist assimilation when put in situation hostile to Christian faith. That illustrates the hidden power of saving grace to counteract peer pressure.