Aaron Temkin Beck (born July 18, 1921) is an American psychiatrist who is professor emeritus in the department of psychiatry at the University of Pennsylvania. He is regarded as the father of both cognitive therapy and cognitive behavioral therapy. His pioneering theories are widely used in the treatment of clinical depression and various anxiety disorders. Beck also developed self-report measures of depression and anxiety, notably the Beck Depression Inventory (BDI) which became one of the most widely used instruments for measuring depression severity. In 1994, he and his daughter, psychologist Judith S. Beck, founded the nonprofit Beck Institute for Cognitive Behavior Therapy providing CBT treatment, training, and research. Beck currently serves as President Emeritus of the organization.