Quote Originally Posted by William Lane Craig
From Craig's "Defenders" podcasts:

This question would be: what about a person who claims to have been a Christian – claims that he has tasted the Holy Spirit and known God – and then walks away from it and apostatizes and throws Christ out of his life? There are really two views about this. The one view is that he wasn’t really regenerate in the first place. He wasn’t really born again – he just had an emotional experience or went forward at an altar call, but he never really had that inner witness of the Holy Spirit. The other view would be that that person really was a regenerate Christian, he knew the Holy Spirit, but because of sin in his life he hardened his heart against the Holy Spirit and finally cast Jesus Christ out of his life and committed apostasy. This is what the author of the book of Hebrews warns about in chapters 6 and 10 – about those who have tasted the goodness of the Lord and the power of the Holy Spirit and the age to come, and then they commit apostasy. On that view they have lost their salvation. They have thrown Christ out of their life.

If you were to ask me what do I think – I tend to believe the latter. I think that if you take these warnings in Hebrews seriously, it suggests that a person, a born-again Christian, can commit apostasy and throw Christ out of his life and lose salvation. That is why I said earlier that the witness of the Holy Spirit isn’t indubitable, it is not irresistible, we can grieve the Holy Spirit through sin, we can quench the Holy Spirit by refusing to submit our lives to him, and, I think, ultimately, the Scripture teaches that you can cast the Holy Spirit out of your life by committing apostasy and renouncing Jesus Christ. The Scripture has very stern warnings about that. But again, I want to repeat, one’s views on the question of “eternal security” or “perseverance of the saints” doesn’t affect whether or not [belief in] the God of the Bible is properly basic. Whichever view you take, you can still maintain on the basis of the witness of the Holy Spirit that someone who has the witness of the Holy Spirit and attends to it can know with confidence that Christianity is true because the Holy Spirit gives him assurance that it is true.
Craig is wrong about Heb. 6 and 10. Someone who comes close to the door of salvation but doesn't enter in was never born-again to begin with. It would have been better they never knew Jesus similar to what is said in 2 Pet. 2.21. This interpretation reconciles with John 10.28 which says a person born-again "they shall never perish." Perhaps Craig blocks this passage out of his awareness.

Can a person be born-again, again, and again? I think that makes God look foolish if it were true that He doesn't have the foresight or power to know whom to give His life too (open theism). Plus, it violates initial salvation not by works lest anyone should boast. Craig boasts in his flesh to be able to remove it or keep it in his own strength.

A person who gives their life to Christ receives the Jesus who keeps, knowing and accepting we can't keep it ourselves. Otherwise, one is filled with the pride of life.

Grieving the Holy Spirit should not be construed as losing the Holy Spirit. That's over-assuming. The Holy Spirit still indwells the believer, but the believer is behaving carnally. As Paul said, there are both carnal and spiritual Christians which shall be rewarded. The Holy Spirit is irresistible only in the sense that He keeps His elect because this is Whom His elect gave their life to, that is, to be kept.

If you worship a false Christ of salvation by works, you wouldn't be saved. When you come before the Great White Throne you won't repent, and in the New City and New Earth there is no sin.