"God promises that He will keep His own, so such a person would not have been kept, making their salvation impossible. The point is the permanency, not whether a person makes an occasional mistake."
Sounds like once saved always saved, FK. What about this? These fellows (Hymenaeus and Alexander) apparently had the faith, or so +Paul would have us believe, but then rejected it:
"Timothy, my son, I give you this instruction in keeping with the prophecies once made about you, so that by following them you may fight the good fight, holding on to faith and a good conscience. Some have rejected these and so have shipwrecked their faith." 1 Timothy 1:18-19
The issue of apostasy comes up many times in the NT, especially in the Epistles.
"Timothy, my son, I give you this instruction in keeping with the prophecies once made about you, so that by following them you may fight the good fight, holding on to faith and a good conscience. Some have rejected these and so have shipwrecked their faith." 1 Timothy 1:18-19
I don't see any inconsistency. "These" refers to faith and a good conscience. Many people "claim" to have "these", but in fact do not. Those who are shipwrecked have fallen away permanently, and are lost because they were never saved in the first place. Hymenaeus and Alexander must have been such, as they are both labeled as blasphemers in verse 20. Hymenaeus is also mentioned later as a blasphemer:
2 Tim. 2:17-18 : 17 Their teaching will spread like gangrene. Among them are Hymenaeus and Philetus, 18 who have wandered away from the truth. They say that the resurrection has already taken place, and they destroy the faith of some.
It appears to me that in order to teach this error, that they could not have ever been truly saved. The footnote in my Bible suggests that they were akin with Gnostics.