Human life implies adventure, and there is no adventure without struggles and dangers.

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.

... each type of civilization has had diseases peculiar to it and at each period the various social groups in any community also have differed in this regard.

The word "wilderness" occurs approximately three hundred times in the Bible, and all its meanings are derogatory.

Biologically, man is still the great amateur of the animal kingdom; he is unique in his lack of anatomical and physiological specialization.

The belief that we can manage the Earth and improve on Nature is probably the ultimate expression of human conceit, but it has deep roots in the past and is almost universal.

Each civilization has its own kind of pestilence and can control it only by reforming itself.