“Every man is surrounded by a neighborhood of voluntary spies.”

On Human Nature (1978), Ch.3 Development

Source: Creatures of Forever

Source: War and Peace

Source: Starship Troopers

Speech in Springfield Illinois (24 October 1952)
Context: I do not believe it is man's destiny to compress this once boundless earth into a small neighborhood, the better to destroy it. Nor do I believe it is in the nature of man to strike eternally at the image of himself, and therefore of God. I profoundly believe that there is on this horizon, as yet only dimly perceived, a new dawn of conscience. In that purer light, people will come to see themselves in each other, which is to say they will make themselves known to one another by their similarities rather than by their differences. Man's knowledge of things will begin to be matched by man's knowledge of self. The significance of a smaller world will be measured not in terms of military advantage, but in terms of advantage for the human community. It will be the triumph of the heartbeat over the drumbeat.
These are my beliefs and I hold them deeply, but they would be without any inner meaning for me unless I felt that they were also the deep beliefs of human beings everywhere. And the proof of this, to my mind, is the very existence of the United Nations.

Contingencies of Reinforcement: A Theoretical Analysis (1969).
Source: Contingencies Of Reinforcement: A Theoretical Analysis

i.e., the natural world
Quoted in "Deutsche Technik", May 1938, p. 209.