One of the reasons why we talk past each other on the question of apostasy is that we succumb to the common mistake of choosing which verses are the “clear” ones. A hermeneutical rule of thumb (quite a good one, I should add) is that unclear verses should be interpreted in the light of the clear ones. But however wise this is — and it is wise — we also have to distinguish between verses which are unclear, and verses that are excruciatingly clear but which conflict with the received interpretation.
It is this latter situation which causes Christians to arbitrarily dub these as the clear verses, and those other verses as the ones which must be massaged. On this question of apostasy, both Calvinists and Arminians do this. Calvinists take the verses outlining God’s sovereignty at face value (which they should do), and explain away the apostasy passages. Arminians take the apostasy passages at face value, and explain away the glorious promises of a guaranteed perseverance. Thought experiment. What would happen if you took them all at face value? You would get in trouble with everybody, like the guy in the Civil War who tried to make peace by walking in between the armies with a blue coat and gray trousers.
The Bible emphasizes, through some of its illustrations, a certain continuity of type between the converted and unconverted covenant member. In the parable of the sower, the converted and unconverted both spring from the same seed, and they are both wheat. The Bible emphasizes, in other illustrations, a radical discontinuity of type between the two — a sow that is washed is always a sow. Tares are not wheat — they are an alien plant in the wheat field. We should take both kinds of illustration at face value. In one respect, there is a radical gulf between converted and unconverted covenant members, a gulf as wide as the distance between Heaven and Hell. In another respect, there is a shared covenantal identity of some sort. Fruitful and fruitless branches are found in the Vine, although the fruitless ones are not found there for long. Fruitful and fruitless branches are found in the olive tree of the true Israel — although the only way to remain in that tree is by having the faith of Abraham.
So much is a statement of the problem. What is the solution to the problem? How can we take both kinds of passages at face value? There is only one way — and that is by emphasizing, in its right biblical balance, the absolute necessity of the new birth for every last human being, not excluding those who are baptized Christians.
Even in the parable of the sower, note how Jesus explains the difference between different kinds of wheat. The wheat in rocky soil sprang up quickly. It sprang up from the seed that was sown. It was wheat, but it was wheat that died, wheat that did not persevere to the harvest. And why? Jesus says that it was because that man had “no root in himself” (ouk rhitzan en auto). This wheat did not have within itself something that the abundant wheat did have (Matt. 13:21). You must be converted to God.
Jesus told a teacher in Israel once that he needed to be born again. Israel today, the new Israel, is filled to overflowing with that same kind of teacher.