and whom he called, them he also justified: and whom he justified, them he also glorified.
I see no way that justification can be abdicated! Do you?
Those are the 2 possibilities I can think of J.
This is a tough issue for me because my tendency would be to fall back on my baptist upbringing and just say that it's impossible to lose one's salvation and that anyone who doesn't live it never really had it.
The difficulty there is all the scripture that speaks of conditional continuation.
Those conditional verses don't say so, but the assumption would have to be that God strips them of or permits to the abdicate their justification. To nail that down one would need a verse that specifically deals with that issue. I simply cannot think of one.
The "P", however, is not the issue with calvinism. The "P" does not cause the "U" to stand or fall. The "I", though, does. The "U" cannot stand if the "I" falls.