“If there is one mental vice, indeed, which sets off the American people from all other folks who walk the earth … it is that of assuming that every human act must be either right or wrong, and that ninety-nine percent of them are wrong.”

Ron English's Fauxlosophy: Volume 2 (2022)

Source: Entwined with You

Spoken statement (c. 1903); published in Harper's Monthly (September 1932).
Variants:
None of my inventions came by accident. I see a worthwhile need to be met and I make trial after trial until it comes. What it boils down to is one per cent inspiration and ninety-nine percent perspiration.
Statement in a press conference (1929), as quoted in Uncommon Friends: Life with Thomas Edison, Henry Ford, Harvey Firestone, Alexis Carrel & Charles Lindbergh (1987) by James D. Newton, p. 24.
Variant forms without early citation: "Genius is one percent inspiration and ninety-nine percent perspiration. Accordingly, a 'genius' is often merely a talented person who has done all of his or her homework."
"Genius: one percent inspiration and 99 percent perspiration."
1900s
Variant: Genius is one per cent inspiration and ninety nine perspiration.

Source: The Secret

The Art of Peace (1992)

Source: The Lost World

Remarks in the Senate http://www.bartleby.com/73/1641.html (29 February 1872) He was here responding to the famous slogan derived from a statement of Stephen Decatur: "Our country! In her intercourse with foreign nations, may she always be in the right; but our country, right or wrong."

Prayers For The Assassin (2006)