Those of OT Israel who believed that their "chosenness" granted them "eternal security", and thus permitted them to behave as they pleased, ended up as corpses by the thousands.
They are lessons for those who think similarly today. God in His mercy withholds judgment today, but disaster awaits in eternity if there is not a return to the faith.
There will be multitudes in hell who believed that they could live as they pleased because they were "eternally secure".
God is the giver of faith, which we know is His assurance of things hoped for, the conviction by the Holy Spirit of things not seen (Hebrews 11:1). By grace we have been saved through faith, and this is not our own doing, it is the gift of God, not a result of works, so that no one may boast (Ephesians 2:8). And once given saving faith, we are by God’s power being guarded through faith for a salvation ready to be revealed in the last time (1 Peter 1:5). We don't create or manufacture our own faith and thereby contribute that in our salvation, nor do we maintain it in us; faith is not a work of man, but of God. Jesus is the author/founder and finisher/perfecter of our faith (Hebrews 12:2).
There is absolutely no doubt that Charles Templeton was regenerate of heart until he repudiated his regeneration.
Sure, well, anybody can repudiate anything, for sure. But with regard to regeneration of the heart by the Holy Spirit ~ we don't in any way regenerate our own hearts and somehow make ourselves born again (surely that's not what you mean to suggest) ~ it is invincible. If He does it, it is, and it always will be: If God begins a good work in us, He will ~
will ~ bring it to completion at the day of Christ (Philippians 1:6). God's purposes cannot be thwarted (Job 42:2). Either Charles Templeton was never regenerate of heart in the first place, or, possibly, he only
thought he was no longer or not regenerate.
Hebrews 6:4-6 is conclusive, as it speaks of "those who were once enlightened, and have tasted of the heavenly gift, and were made partakers of the Holy Ghost, and have tasted the good word of God, and the powers of the world to come". Those descriptions can only refer to those who had experienced salvation.
What the writer of Hebrews is saying here is that these people have
heard the truth explained and thus have also
learned of God's Word, and experienced the benefits therein and of the presence of the Spirit and His work around them. But faith comes by hearing (Paul again in Romans 10), but we know that not all who hear are given saving faith. The fact is that God, by His Spirit is not at work
in them (see Philippians 2:13) or bearing fruit
through them (Galatians 5). There are people in our churches today who look the part, to others and even to themselves, but they do not have ~ have not been given ~ faith... have not been born again from above. For many, this will not remain the case; God will at some point call them and begin His good work in them, but for others ~ and this apparently was the case with Charles Templeton ~ not so much, and they eventually fall away. Again, as John says of such folks, "They went out from us, but they were not of us; for if they had been of us, they would have continued with us... (b)ut they went out, that it might become plain that they all are not of us" (1 John 4:19).
The same Paul who wrote Romans 8:35-39 et al, wrote Hebrews 6:4-6.
There's some evidence that seems to support that, but no one can say for sure. But, even if so, he also wrote all his other letters, too, including the above-mentioned letters to the Ephesians, the Galatians, and the Philippians. I do agree that he didn't contradict himself, but... :)
Grace and peace to you.