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.

Eradication of microbial disease is a will-o'-the-wisp; pursuing it leads into a morass of hazy biological concepts and half truths.

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

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

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.

...Search for the cause may be a hopeless pursuit because most disease states are the indirect outcome of a constellation of circumstances.