Also upheld by such ancients as Augustine and, of course, is Biblical. It's hardly a fringe Christian belief. But to be "saved" is to be regenerated, which means you don't go around binding, torturing and killing innocent people.
Nope, One of the books of St, Augustine entitled Treaties on Rebuke and Grace, he explicitly taught that salvation can be lost if we do not live in accordance to our Christian faith and relapse to our sinful ways.
If, however, being already regenerate and justified, he relapses of his own will into an evil life, assuredly he cannot say, “I have not received”, because of his own free choice to evil he has lost the grace of God, that he had received. Treaties on Rebuke and Grace, p.9