Here on Earth, Anthroposophy seems to be so much theory and the human being in his waking state has no consciousness of what is spiritually life-giving but nevertheless objectively present. After death man is a direct witness of how the forces he took into himself together with the spiritual teachings received during his life on Earth have an organising, vitalising, strengthening effect upon what is within his being when he is preparing for a new incarnation.
In this way spiritual teaching actually becomes part of the evolution of humanity. But if this spiritual teaching were to be rejected — at the present time it suffices if only a few accept it but in the future more and more individuals must do so — then, as they return to incarnations on Earth, human beings will gradually find that they lack the life-giving forces they need. Decadence and atrophy would set in during the subsequent incarnation. Human beings would quickly wither, be prematurely wrinkled. Decadence of physical humanity would set in if the spiritual forces were not received.
Source: Rudolf Steiner – GA 141 – Between Death and Rebirth: Lecture Four – 10th December 1912
Translated by E. H. Goddard & D. S. Osmond