We need teachers who are able to educate children on the basis of a conception of the world that understands the true being of man. This was the thought underlying the Course I gave to the teachers when the Waldorf School at Stuttgart was founded. All the principles of the art of education as expounded in that Course strive in the direction of making men and women out of the children who are being educated — men and women in whom lungs, liver, heart, stomach, will be healthy in later life because, in childhood, they were helped to develop their life-functions in the right way, because, in effect, the soul worked in the right way.
This conception of the world will never give a materialistic interpretation of the old saying, Mens sana in corpore sano. Interpreted in the materialistic sense this means: If the body is healthy, if it has been made healthy by all kinds of physical methods, then it will of itself be the bearer of a healthy soul. Now this is pure nonsense. The only real meaning of the phrase is this: a healthy body bears witness to the fact that the force of healthy soul has built it up, moulded it, made it healthy. A healthy body proves that a healthy soul has worked within it. That is the right interpretation of the phrase — and only in this sense can it be a principle of true hygiene.
Source: Rudolf Steiner – GA 314 – Hygiene – a Social Problem – Dornach, April 7th, 1920