There’s even biblical support for this claim. First John 2:19 implies that those who are true believers will not change their minds: “They went out from us,” it begins, “but they were not of us; for if they had been of us, they would no doubt have continued with us…” (Of course, as with just about anything, the Bible can also be used in support of the opposing view. Thus, I Timothy 4:1 states that “…in the latter times some shall depart from the faith…” – in part, no doubt, because the faith contradicts itself.)
Now, if these people who claim they were once believers were never real Christians, then either they are mistaken or they are lying. But it’s unlikely that they are all lying – that’s quite a large number of people, after all, and you’d expect some of them at least to have admitted the deception by now. What the deniers of Christian apostasy appear to suppose, then, is that most or all of these people are mistaken: they thought they were Christians, but they were fooling themselves. They had perhaps nominally adopted the religion of their parents, but hadn’t really accepted Jesus as their savior – even if, like Barker and Loftus, they thought they had.
But now here’s the problem. If all this is true, then how can anyone who currently calls himself a Christian be sure that he really is? If someone can be wrong about their beliefs this way, then it seems that those who at present regard themselves as believers may also be confused. So how can anyone know that they are among the saved? It appears that denying the existence of ex-Christians comes at a heavy price.