Source: The Wretched of the Earth
“Liberals can understand everything but people
who don't understand them.”
Sun-Faced Buddha, Moon-Faced Buddha lecture at the Zen Mountain Center (17 August 1971) http://suzukiroshi.sfzc.org/archives/index.cgi/710817V.html
Context: Communication is — start by understanding — your own understanding about people. Even though you want them to understand you, you know, it is — unless you understand people, it is almost impossible. Don't you think so? Only when you understand people, they may understand you. So even though you do not say anything, if you understand people there is some communication.
“You can only understand people if you feel them in yourself.”
“You can have everything in life that you want if you just give enough other people what they want.”
Secrets of Closing the Sale (1984)
Variant: You can get everything in life you want if you will just help enough other people get what they want.
The Captive Mind (1953)
Context: Vulgarized knowledge characteristically gives birth to a feeling that everything is understandable and explained. It is like a system of bridges built over chasms. One can travel boldly ahead over these bridges, ignoring the chasms. It is forbidden to look down into them; but that, alas, does not alter the fact that they exist.
“You do not really understand something unless you can explain it to your grandmother.”
variant: If you can't explain something to a six-year-old, you really don't understand it yourself.
variant: If you can't explain it simply, you don't understand it well enough.
Frequently attributed to Richard Feynman
Probably based on a similar quote about explaining physics to a "barmaid" by Ernest Rutherford
Page 418 of Einstein: His Life and Times (1972) by Ronald W. Clark says that Louis de Broglie did attribute a similar statement to Einstein:
: To de Broglie, Einstein revealed an instinctive reason for his inability to accept the purely statistical interpretation of wave mechanics. It was a reason which linked him with Rutherford, who used to state that "it should be possible to explain the laws of physics to a barmaid." Einstein, having a final discussion with de Broglie on the platform of the Gare du Nord in Paris, whence they had traveled from Brussels to attend the Fresnel centenary celebrations, said "that all physical theories, their mathematical expressions apart ought to lend themselves to so simple a description 'that even a child could understand them.' "
The de Broglie quote is from his 1962 book New Perspectives in Physics, p. 184 http://books.google.com/books?id=xY45AAAAMAAJ&q=%22mathematical+expression+apart%22#search_anchor.
Cf. this quote from David Hilbert's talk Mathematical Problems given in 1900 before the International Congress of Mathematicians:
: "A mathematical theory is not to be considered complete until you have made it so clear that you can explain it to the first man whom you meet on the street."
Cf. this quote from Kurt Vonnegut's novel Cat's Cradle:
: Dr. Hoenikker used to say that any scientist who couldn't explain to an eight-year-old what he was doing was a charlatan.
Misattributed
Vol. I, Part III: The Evolution of Life, Ch. 3 : General Aspects of the Evolution Hypothesis; compare: "As nine months go to the shaping an infant ripe for his birth, / So many a million of ages have gone to the making of man", Alfred Lord Tennyson, Maud (1855)
Principles of Biology (1864)
