The highway is the raised inner road, the channel up the spine along which consciousness travels back to its source. It is called holy because it is whole, the way made single and clean, and the unclean cannot pass because the mixed and animal pulls of the flesh have no traction on it; only the purified current rises there. The path is so direct that even the simple, the ones without learning or cleverness, cannot lose their way on it.
What happens in a person is that a plain, unmistakable route opens upward. Once the energy is clean it climbs of itself, and no lack of understanding can send it wrong, because the road runs one way only.
The highway: the raised inner road, the channel up the spine by which purified consciousness travels back to its source.
The unclean: the mixed, animal pulls of the flesh that can gain no foothold on the risen way.