The UNIX Philosophy

Ken Thompson has an automobile which he helped design. Unlike most
automobiles, it has neither speedometer, nor gas gauge, nor any of the
other numerous idiot lights which plague the modern driver. Rather, if the
driver makes a mistake, a GIANT ? lights up in the center of the
dashboard. The experienced driver, says he, will usually know
whats wrong.

Original source unknown; found on Joseph Evans (Electrical and
Computer Engineering professor at Kansas University) door.