Between death and a new birth, we learn to read the conditions here on earth in relationship with the spiritual world. Try to realize this, try to imagine these conditions. Then you will have to confess that it is, indeed, deeply significant to say that the world which we first learn to know through our senses and our understanding is an illusion, a Maya. As soon as we approach the real world, we find that the world that we know is related to this real world in the same way in which the reflection in the mirror is related to the living reality before the mirror, which is reflected in it.
Source: Rudolf Steiner – GA 179 – Historical Necessity and Freewill: Lecture 4: The Rhythmical Relationship of Man with the Universe and with the World of the Dead – Dornach, December 11, 1917