Every human being lived behind an impenetrable wall of choking mist within which no other but he existed. Occasionally there were the dim signals from deep within the cavern in which another man was located — so that each might grope toward the other. Yet because they did not know one another, and could not understand one another, and dared not trust one another, and felt from infancy the terrors and insecurity of that ultimate isolation — there was the hunted fear of man for man, the savage rapacity of man toward man.

Chapter 8 Seldon's Plan (in part II, Search by the Foundation originally published as —And Now You Don't in Astounding (November and December 1949 and January 1950)) - The Foundation series - Second Foundation (1953)