It ain't so much what people don't know that hurts as what they know that ain't so.
Source: In Pearls of Wisdom, ed. J. Agel and W. Glanze, 1987.
-- Artemus Ward, (Apr 26 1834-1867), US humorist; One of the most popular 19th-century American humorists, whose lecture techniques exercised much influence on such humorists as Mark Twain.