All relationships of people to each other rest, as a matter of course, upon the precondition that they know something about each other. The merchant knows that his correspondent wants to buy at the lowest price and to sell at the highest price. The teacher knows that he may credit to the pupil a certain quality and quantity of information. Within each social stratum the individual knows approximately what measure of culture he has to presuppose in each other individual.

p. 441: First lines of the article. - The Sociology of Secrecy and of Secret Societies (1906)