IMPARTIAL, adj. Unable to perceive any promise of personal advantage from espousing either side of a controversy or adopting either of two conflicting opinions.

Ambrose Bierce (1842–1914?) American writer and journalist

“Impartial,” The Cynic’s Word Book (1906)
    (Source)

Included in The Devil's Dictionary (1911). Originally published in the "Devil's Dictionary" column in the San Francisco Wasp (1885-09-12).