“Humor is the atmosphere in which grace most flourishes.”

Source: Victim Prime (1987), Chapter 48 (pp. 187-188)

"Science and Dictatorship," in Dictatorship on Its Trial, by Eminent Leaders of Modern Thought (1930) - later as Dictatorship on Trial (1931), Otto Forst de Battaglia (1889-1965), ed., Huntley Paterson, trans., introduction by Winston Churchill, George G. Harrap & Co., (Reprinted 1977, Beaufort Books Inc., p. 107. https://books.google.com/books?id=IjsiAAAAMAAJ&dq=9780836916072&focus=searchwithinvolume&q=%22only+in+an+atmosphere+of+free+speech%22 https://books.google.com/books?id=alq9M3_8qIcC&dq=9780836916072&hl=en&sa=X&ved=0ahUKEwj9w8nJkYfKAhUL12MKHf5uCscQ6AEIHDAA http://babel.hathitrust.org/cgi/pt/search?q1=%22Science%20can%20flourish%20only%20in%20an%20atmosphere%20of%20free%20speech%22;id=uc1.%24b47955;view=1up;seq=9;start=1;sz=10;page=search;orient=0 http://catalog.hathitrust.org/Record/000590821
1930s
Context: A dictatorship means muzzles all round and consequently stultification. Science can flourish only in an atmosphere of free speech.

Un Art de Vivre (The Art of Living) (1939), The Art of Loving

The Big Picture: An American Commentary (1991)

1930s
Original: (de) Die Diktatur bringt den Maulkorb und dieser die Stumpfheit. Wissenschaft kann nur gedeihen in einer Atmosphäre des Freien Wortes.

"Science and Dictatorship," in Dictatorship on Its Trial, by Eminent Leaders of Modern Thought (1930) - later as Dictatorship on Trial (1931), Otto Forst de Battaglia (1889-1965), ed., Huntley Paterson, trans., introduction by Winston Churchill, George G. Harrap & Co., (Reprinted 1977, Beaufort Books Inc., ISBN 0836916077 ISBN 9780836916072 p. 107. https://books.google.com/books?id=IjsiAAAAMAAJ&dq=9780836916072&focus=searchwithinvolume&q=%22only+in+an+atmosphere+of+free+speech%22 https://books.google.com/books?id=alq9M3_8qIcC&dq=9780836916072&hl=en&sa=X&ved=0ahUKEwj9w8nJkYfKAhUL12MKHf5uCscQ6AEIHDAA http://babel.hathitrust.org/cgi/pt/search?q1=%22Science%20can%20flourish%20only%20in%20an%20atmosphere%20of%20free%20speech%22;id=uc1.%24b47955;view=1up;seq=9;start=1;sz=10;page=search;orient=0 http://catalog.hathitrust.org/Record/000590821 Original text of this "nineteen word essay" https://www.google.com/#tbm=bks&q=%22Albert+Einstein+in+his+nineteen+word+essay+on+Science+and+Dictatorship%22 appears under the German title, "Wissenschaft und Diktatur" in Prozess der Diktatur (1930), Otto Forst de Battaglia (1889-1965), ed., Amalthea-Verlag, p.108. https://books.google.com/books?id=Q9DRAAAAMAAJ&dq=editions%3ATP1X5VVtHxAC&focus=searchwithinvolume&q=%22Die+Diktatur+bringt+den+maulkorb+und+dieser+die+stumpfheit.+Wissenschaft+kann+nur+gedeihen+in+einer+Atmosph%C3%A4re+des+freien+Wortes%22

Book VI, 6.34; "they have abundance of gold and silver, and these make war, like other things, go smoothly" ( trans. http://www.classicpersuasion.org/pw/thucydides/jthucbk6rv2.htm Benjamin Jowett)
History of the Peloponnesian War, Book VI

Source: Quotes from secondary sources, Dictionary of Burning Words of Brilliant Writers, 1895, P. 294.

Letter http://books.google.com/books?id=R8ksAAAAIAAJ&q=%22I+own+any+form+of+humor+shows+fear+and+inferiority+Irony+is+simply+a+kind+of+guardedness+So+is+a+twinkle+It+keeps+the+reader+from+criticism%22+%22Humor+is+the+most+engaging+cowardice%22&pg=PA166#v=onepage to Louis Untermeyer (10 March 1924)
General sources
Context: I own any form of humor shows fear and inferiority. Irony is simply a kind of guardedness. So is a twinkle. It keeps the reader from criticism. Whittier, when he shows any style at all is probably a greater person than Longfellow as he is lifted priestlike above consideration of the scornful. Belief is better than anything else, and it is best when rapt, above paying its respects to anybody's doubt whatsoever. At bottom the world isn't a joke. We only joke about it to avoid an issue with someone to let someone know that we know he's there with his questions: to disarm him by seeming to have heard and done justice to this side of the standing argument. Humor is the most engaging cowardice.