“[A proverb is] one man's wit, and all men's wisdom.”
Remark to James Mackintosh on October 6, 1830, reported in his posthumous memoir, Memoirs of the Life of the Right Honourable Sir James Mackintosh, Vol. 2 (1836), p. 472 http://books.google.com/books?id=wHM4AAAAYAAJ&q=%22one+man's+wit+and+all+men's+wisdom%22&pg=PA472#v=onepage
Variante: [A proverb is] the wisdom of many and the wit of one.