Source: 1940s, Economic Analysis, 1941, p. 42 as cited in: Vernon L. Smith (1991) Papers in Experimental Economics. p. 516
“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.”
Source: The Sociology of Secrecy and of Secret Societies (1906), p. 441: First lines of the article.
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Georg Simmel 27
German sociologist, philosopher, and critic 1858–1918Related quotes

La guerre, c'est un massacre de gens qui ne se connaissent pas, au profit de gens qui se connaissent, mais ne se massacrent pas.
Bizarre, issues 24-31 (1962), p. 102
This apocryphal quote from Paul Valéry is never precisely sourced: neither on the internet nor in the works we have consulted. See: https://www.guichetdusavoir.org/question/voir/52650

Source: The Tales of Alvin Maker, Prentice Alvin (1989), Chapter 2.

In reference to the Alabama Council on Human Relations, an organization which was joined by King, whose church's meeting room was used to hold monthly meetings for the Montgomery chapter the council. Stride Toward Freedom: The Montgomery Story (1958)
1950s
Context: Although the Montgomery council never had a large membership, it played an important role. As the only truly interracial group in Montgomery, it served to keep the desperately needed channels of communication open between the races.
Men often hate each other because they fear each other; they fear each other because they don't know each other; they don't know each other because they can not communicate; they can not communicate because they are separated. In providing an avenue of communication, the council was fulfilling a necessary condition for better race relations in the South.

Grant (1932) "Christmas Greetings from the First Presidency," Improvement Era Dec. 1932, 67.; Cited in " Heber J. Grant, Served 1918–1945 http://www.lds.org/churchhistory/presidents/controllers/potcController.jsp?leader=7&topic=quotes" on ids.org

Cassandra (1860)
Context: It is very well to say "be prudent, be careful, try to know each other." But how are you to know each other?
Unless a woman had lost all pride, how is it possible for her, under the eyes of all her family, to indulge in long exclusive conversations with a man? "Such a thing" must not take place till after her "engagement." And how is she to make an engagement, if "such a thing" has not taken place?

“Paul and I know each other on a lot of different levels that very few people know about.”

Out of Control: The New Biology of Machines, Social Systems and the Economic World (1995)

On the writing process of Mark Morton and Wille Adler, the guitarists of Lamb of God.
Making of Sacrament DVD