Who would want to live in a world that is just not quite fatal?
The desert sky is encircling, majestic, terrible.
The human cardiovascular system evolved as part of the physiology of [prehistoric] hunters, who ran for their lives.
There is a secret person undamaged in every individual.
When men do not run they are likely to die prematurely from dysfunction of the heart and vascular systems or from disabling chronic disease.
The natural world is not only a set of constraints but of contexts within which we can more fully realize our dreams.