Pathological states are the consequence of several determinate factors acting simultaneously...The manifestations of any given agent differ profoundly from one person to another. ...Each noxious agent can express itself by a great variety of different pathological states. ...Different agents can elicit similar reactions. ...The total environment and the (interior medium) constitute a multifactorial system.

As far as life is concerned, there is no such thing as "Nature". There are only homes. Home is that environment to which the individual has become adapted; and almost everything is unnatural outside his range of adaptation. Harmonious equilibrium with nature is an abstract concept with a Platonic beauty but lacking the flesh and blood of life. It fails, in particular, to convey the creative emergent quality of human existence.

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.

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

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

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