One advantage of exhibiting a hierarchy of systems in this way is that it gives us some idea of the present gaps in both theoretical and empirical knowledge. Adequate theoretical models extend up to about the fourth level, and not much beyond. Empirical knowledge is deficient at practically all levels.

... the fouling of the nest which has been typical of man's activity in the past on a local scale now seems to be extending to the whole world society.

All knowledge is gained through an orderly loss of information.

Humble, honest, ignorance is one of the finest flowers of the human spirit

Because of his capacity for abstract communications and language and his ability to enter in imagination into the lives of others, man is able to build organizations of a size and complexity far beyond those of the lower animals.

The trouble with taxonomic boxes is... that that they tend to be empty, however beautiful they are on the outside.

Deciding under uncertainty is bad enough, but deciding under an illusion of certainty is catastrophic.