Social evolution may be the result of intention, but it rarely, if ever, produces the result intended.

With reference to life there is not one nature; there are only associations of states and circumstances, varying from place to place and from time to time.

... men as a rule are more preoccupied with the dangers that threaten their life than interested in the biological forces on which they depend for a constructive existence.

Human diversity makes tolerance more than a virtue; it makes it a requirement for survival.

The earth is literally our mother, not only because we depend on her for nurture and shelter but even more because the human sepcies has been shaped by her in the womb of evolution. Our salvation depends upon our ability to create a religion of nature.

The most important pathological effects of pollution are extremely delayed and indirect.

Human destiny is bound to remain a gamble, because at some unpredictable time and in some unforeseeable manner nature will strike back.