If there is much of these, the astral body is strongly vitalized, and will persist for a long time; if there is but little, the astral body has less vitality, and he will soon be able to cast that vehicle aside in turn.

When that is done he finds himself living in his mental body.

The strength of that depends upon the nature of the thoughts to which he has habituated himself, and usually his stay at this level is a long one.

At last it comes to an end, and he casts aside the mental body in turn, and is once more the ego in his own world.
Owing to lack of development, he is as yet but partially conscious in that world; the vibrations of its matter are too rapid to make any impression upon him, just as the ultra-violet rays are too rapid to make any impression upon our eyes.

After a rest there, he feels the desire to descend to a level where the undulations are perceptible to him, in order that he may feel himself to be fully alive; so he repeats the process of descent into denser matter, and assumes once more a mental, an astral and a physical body.