Man shapes himself through decisions that shape his environment.

Man not only survives and functions in his environment, he shapes it and he is shaped by it.

The mechanisms of vis medicatrix naturæ—the most healing power of nature—are so effective that most diseases are self-terminating.

There is an unbroken continuum from the wisdom of the body to the wisdom of the mind, from the wisdom of the individual to the wisdom of the race.

Any attempt to shape the world and modify human personality in order to create a self-chosen pattern of life involves many unknown consequences. Human destiny is bound to remain a gamble, because at some unpredictable time and in some unforeseeable manner nature will strike back. The multiplicity of determinants which affect biological systems limits the power of the experimental method to predict their trends and behavior.

Men are naturally most impressed by diseases which have obvious manifestations, yet some of their worst enemies creep on them unobtrusively.

The very process of living is a continual interplay between the individual and his environment, often taking the form of a struggle resulting in injury or disease.