"Man is a creature whose evolutionary environment has been the open air. His nerves, muscles, and senses have developed across three million years in contiguity with natural earth, crude stone, live wood, wind, and rain. Now this creature is suddenly--on the geologic scale, instantaneously--shifted to an unnatural environment of metal and glass, plastic and plywood, to which his psychic substrata lack all compatibility. The wonder is not that we have so much mental instability but so little."