“Let every man mind his own business.”
Source: Don Quixote de la Mancha (1605–1615), Part I, Book III, Ch. 8.
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Miguel de Cervantes 178
Spanish novelist, poet, and playwright 1547–1616Related quotes

“Let every man choose his own guardian and guide.”
The Caesars (c. 361)
Context: Know all ye mortals who have entered this contest,
that according to our laws and decrees the victor is
allowed to exult but the vanquished must not complain.
Depart then wherever you please, and in future live
every one of you under the guidance of the gods.
Let every man choose his own guardian and guide.

Pericles commenting the participation of Athenian citizens in politics, as quoted in Models of Democracy (2006) by David Held, Stanford University Press, p. 14. Book II, chapter 40.

“An Anarchist is one who minds his own business.”
The Better Part (1901)
Context: I AM an Anarchist.
All good men are Anarchists.
All cultured, kindly men; all gentlemen; all just men are Anarchists.
Jesus was an Anarchist.
A Monarchist is one who believes a monarch should govern. A Plutocrat believes in the rule of the rich. A Democrat holds that the majority should dictate. An Aristocrat thinks only the wise should decide; while an Anarchist does not believe in government at all. Richard Croker is a Monarchist; Mark Hanna a Plutocrat; Cleveland a Democrat; Cabot Lodge an Aristocrat; William Penn, Henry D. Thoreau, Bronson Alcott and Walt Whitman were Anarchists. An Anarchist is one who minds his own business. An Anarchist does not believe in sending warships across wide oceans to kill brown men, and lay waste rice fields, and burn the homes of people who are fighting for liberty. An Anarchist does not drive women with babes at their breasts and other women with babes unborn, children and old men into the jungle to be devoured by beasts or fever or fear, or die of hunger, homeless, unhouseled and undone.
Destruction, violence, ravages, murder, are perpetrated by statute law..

“The mark of a basic shit is that he can’t mind his own business.”
Though at times attributed to Leary on the internet, no published source of this has been located. It is a misquote of a William S. Burroughs reading entitled M.O.B. from the Giorno Poetry Systems boxed set. M.O.B. was an extension of Burroughs' expression in The Place of Dead Roads (1983), p. 155:
You are a Shit Spotter. It's satisfying work. … We have observed that most of the trouble in the world has been caused by ten to twenty percent of folks who can't mind their own business, because they have no business of their own to mind, any more than a smallpox virus … The mark of a basic shit is that he has to be right.
Misattributed

“No man is a devil in his own mind.”

“Every man's happiness is his own responsibility.”

“Every man prays in his own language.”
Section title and eponymous song of A Concert of Sacred Music (1965).