Reason is man’s faculty for grasping the world by thought, in contradiction to intelligence, which is man’s ability to manipulate the world with the help of thought. 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:Chapter 3. The Human Situation - the Key to Humanistic Psychoanalysis, Man's Needs - as They Stem From the Conditions of His Existence, E. The Need for a Frame of Orientation and Devotion - Reason vs. Irrationality, Page 64
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