Demonstrating the importance of theory for effective clinical practice, this thought-provoking volume brings together leading experts on a range of contemporary cognitive and behavioral approaches. The contributors probe the philosophical and theoretical underpinnings of each model--its assumptions about normal psychological processes, the development and maintenance of psychopathology, and the mechanisms by which therapeutic changes take place. The historical antecedents of the theories are examined and studies that have tested them are reviewed. Vivid case studies show practitioners how theory informs clinical decision making and technique in each of the respective approaches.