A paradox is a truth standing on its head in order to attract attention.
Source, in full
The Review of Reviews, Volume 17 (Jan-July 1898), “The Topic of the Month: The Jubilee of the Awakening of 1848" (April 1898). ("Richard Le Gallienne, who has recently been airing his ambrosial locks in the heated air of American lecture rooms, once told his audience that "a paradox was a truth standing on its head in order to attract attention."")