From Rudolf Arnheim, Parables of Sun Light: Observations on Psychology, the Arts, and the Rest. Berkeley: University of California Press, 1989, p. 346—
The initials "OK" were the signature of [Austrian expressionist artist] Oskar Kokoschka. Every time I use the two letters to mark my approval of one of my editor's changes on the galleys of my next book, I sneakily credit myself with the small creative act of impersonating one of my favorite painters.
