There is nothing material that does not originate from the spirit. What people experience in health and disease stems from their inner attitude, their thoughts. It is certainly a true proverb: What you think today, you will be tomorrow. It should be clear to you that if an era has bad, depraved thoughts, the next generation and the next era have to pay the price physically. It is a true saying: The sins of the fathers will be visited on the future generations. It will not be without consequence that the people of the 19th century began to think in such a grossly materialistic way, to turn their minds away from everything spiritual. What people have thought then will have consequences. And we are not so far removed from the time when peculiar diseases and epidemics will occur in human life! What we call nervousness will occur, at the latest within half a century, in severe measure. Just as plague and cholera and leprosy in the Middle Ages once were rife, so there will be psychic epidemics, diseases of the nervous system in epidemic form. These are the consequences of the fact that people lack a spiritual core in their lives. Where an awareness of this spiritual core as the centre of life is present, there people will become healthy under the influence of a healthy, true worldview.
Source (German): Rudolf Steiner – GA 96 – Ursprungsimpulse der Geisteswissenschaft – Berlin January 29, 1906 (p. 18)
Translated by Nesta Carsten-Krüger