But you may stimulate it from below.

It is possible to stimulate the astral body, at least, from the physical plane, but you do it at the cost of higher evolution a little later on, and the reason you can do it is simple enough.

In the astral body are all the centres of your senses.

You know how after death a man's desires are the same as they were during his physical life.

You know how in dreams your desires resemble desires that you may have in your waking consciousness.