Reason is man's instrument for arriving at the truth, intelligence is man's instrument for manipulating the world more successfully; the former is essentially human, the latter belongs to the animal part of man.
Source: The Sane Society, ch. 3, The Need for a Frame of Orientation and Devotion, 1955.
-- Erich Fromm, (Mar 23 1900-1980), German-US psychoanalyst; He dealt with the problem of Western man coming to terms with sense of isolation, e.g., Escape from Freedom, 1941.