Nobody has true knowledge of the visible world unless he knows something also of two other worlds.
The three worlds are:
The physical world, the scene of human life.
The astral world or the world of soul.
The devachanic world or world of spirit.
These three worlds are not spatially separate. We are surrounded by the things of the physical world which we perceive with our ordinary senses: but the astral world is in this same space; we live in the other two worlds, the astral and devachanic worlds, at the same time as we live in the physical world. The three worlds are wherever we ourselves are, only we do not yet see the two higher worlds — just as a blind man does not see the physical world. But when the “senses of the soul” are opened, the new world, with its new characteristics and new beings, emerges. In proportion as a man acquires new senses, so are new phenomena revealed to him.
Translated by E.H. Goddard & Charles Davy