The Bible is very clear that we cannot misplace, or lose, our salvation -- as though our salvation were a possession of ours, like a set of car keys or something. My salvation is not something I can lose, as though I owned it. Rather, Christ owns us. We have been purchased by Christ, and He owns us. But knowing that this is the case, and having full confidence in the comforting doctrines of eternal election, what do we do with passages like, well . . . like Hebrews 6? There it is, in the Bible. Big as life.
Therefore, leaving the discussion of the elementary principles of Christ, let us go on to perfection, not laying again the foundation of repentance from dead works and of faith toward God, of the doctrine of baptisms, of laying on of hands, of resurrection of the dead, and of eternal judgment. And this we will do if God permits. For it is impossible for those who were once enlightened, and have tasted the heavenly gift, and have become partakers of the Holy Spirit, and have tasted the good word of God and the powers of the age to come, if they fall away, to renew them again to repentance, since they crucify again for themselves the Son of God, and put Him to an open shame. For the earth which drinks in the rain that often comes upon it, and bears herbs useful for those by whom it is cultivated, receives blessing from God; but if it bears thorns and briers, it is rejected and near to being cursed, whose end is to be burned. But, beloved, we are confident of better things concerning you, yes, things that accompany salvation, though we speak in this manner (Heb. 6:1-9).
The author of Hebrews wants to press on beyond basic Christian doctrine. He does not want to abandon this foundation, but he does want to build on it. That foundation is repentance from religion, faith in God, the meaning of the Levitical washings or baptisms in the Law, the laying on of hands, the resurrection, and eternal judgment. He is not content with his readers remaining in an infantile state -- he intends to press on. This is important because remaining in the foundational doctrines without pressing on creates the temptation to apostasy. Those who have been initiated, who have tasted, but who do not press on to know Christ further, are in grave danger. Sticking with the basics only is therefore not a good way to stick to the basics. This is the central problem with pietistic fundamentalism; at the end of the day it is counterproductive and does not defend the things it seeks to defend. The real way to "defend" a foundation is by building on it.
As we come to this passage, we must remember what we have learned throughout the rest of Scripture. First, this passage does not teach that one of the decreed elect can fall from their election. This would make sovereign election meaningless. This would in effect unGod God; to postulate such a thing makes nonsense out of everything. At the same time, this passage is not a hypothetical warning for the members of the church. This is a real letter, written in real time, to a group of baptized Christians who were contemplating real apostasy. So how are we to reconcile these two elements? God's decrees are sure, and these Christians here might fall away.
In order to consider the nature of apostasy, we have to consider the nature of the Church. What is the "real" church? Since the Reformation, Protestants have been accustomed to speak of the invisible church and the visible church. The distinction is much older than the Reformation and actually goes back to Augustine. But Augustine made a series of distinctions, not just one. For example, he also distinguished between the pilgrim church and the eschatological church. A series of layered distinctions helps us to understand the Church from different angles instead of lapsing into an upper story/lower story dualism.
So while the distinction between the visible and invisible church communicates an important truth (one which I affirm), it can lead to misunderstandings and problems if it is affirmed as the only category for understanding the Church. For example, given these "two" churches, which is the real one? Because evangelicals have answered (naturally) that the invisible church is the real one, this has led to the assumption that the visible church is, in some sense, unreal. This has led, in turn, to a disparagement of the visible church. Since the roster of names for the invisible church (the elect) differs from the roster of names for the visible church (all the church directories in the history of the world), then we would obviously give preference to the list that names of the elect, in distinction from the list that includes Bishop Spong, lesbian pastors, and the BTK killer.
If I were to postulate a visible Suzy and an invisible Suzy, it makes sense to ask which one is the "real" one. If the Church is the bride of Christ, which Church is the bride of Christ. Evangelical Christians tend to say that the upper story Church is the bride of Christ, and this leads (whether we want it to or not) to the notion that the churches we attend are nothing more than an earthly approximation of the Church. But if we say, as we must, that the visible Church and the invisible Church are the same Church, then this leads us to ask for a model that allows us to say this. Which is why I would return to another distinction of Augustine's -- the pilgrim Church and the eschatological Church. The terms I have used for this before have been the historical Church and the eschatological Church. If I speak about Suzy on Monday and Suzy on Friday, no one asks who the real Suzy is. It is the same Suzy at different points in time. This remains the case if we talk about Suzy on Monday, and Suzy at Last Trump. The eschatological Church is the same Church as the historical Church, and we have no problem accounting for why the roster of names is different. The eschatological Church is the one, true Church with every blemish removed, and the historical Church is the one, true Church without those blemishes removed.
So when someone is guilty of apostasy, they are falling away from the true Church of Christ, of which he was genuinely a member. He was a genuine member, but not a permanent member. The permanent members of Christ's church are the elect. The blemishes that are removed from the bride of Christ were once part of her, but are no longer part of her. God, who knows the end from the beginning, knows who the elect are. He knows who will be part of the bride at the last day, and He decreed this before the first day. But in the meantime, nothing in plainer in the New Testament than that non-elect people can be covenant members, and attached to Christ. In John 15, Jesus makes it very plain that branches can be cut out of Him, taken away, and burned.
Always remember that apostasy is a real sin committed by real people who fall away from a real, visible Church. The Church they fall away from is the body of Christ, not an earthly attempt to approximate the body of Christ. The churches we worship in on the Lord's Day are the body of Christ.
Without understanding the reality of the covenant which makes up the covenant community of the Church, we cannot possibly make sense of those passages in the New Testament which warn us about falling away. Either we hold to the eternal security and perseverance passages, and twist the covenant warning passages (as many Calvinists do), or we hold to the covenant warning passages, and twist the eternal security passages (as the Arminians do). But all the Bible belongs to all Christians. If we come to understand the doctrines of God's sovereignty over salvation, and the reality of Christ's covenant with the Church, we can take all the Scriptures on these subjects at face value.
This means that the New Covenant is not a covenant without sanctions, without teeth. This means that the New Covenant contains with its ranks a class of people who are covenant-breakers. Those members of the covenant who are not elect (i.e. non-elect church members) receive genuine blessings which prepare them for sticter judgment. An unbelieving rejection of covenant blessings (held in possession) is the worst possible curse. These people have tasted the heavenly gift and the Word of God. As land they received the blessing of rain, but then decided to grow thorns with it. What will happen to them? They will come to burning. The law of Moses saw no curses as terrible as those curses which come upon apostate Christians. The modern baptistic mentality which tries to identify the New Covenant as the elect only does not know what to do with these warning passages, except turn them upside down. But according to the Bible, which is stricter -- the word that came from Sinai or the word that comes from the heavenly Zion? Which causes greater trembling? Which should strike more awe in the believer's heart?
But there remains a word of comfort. The author of Hebrews believes that this apostasy has not happened among his readers. He is convinced of "better things" in their case. However, this does not mean he believes the worse things to be impossible. (If he believed that, he would not have written.) Nevertheless, he is encouraged about their prospects even though he speaks in this manner. And so should we, holding to the same faith, be encouraged.