The common factors have a storied history that started with Saul Rosenzweig’s (1936) classic article "Implicit Common Factors in Diverse Forms of Psychotherapy." In addition to the original invocation of the dodo bird and seminal explication of the common factors of change, Rosenzwieg also provided the best explanation for the common factors, still used today. Namely, given that all approaches achieve roughly similar results, there must be pantheoretical factors accounting for the observed changes beyond the presumed differences among schools.
In 1936, writing in the American Journal of Orthopsychiatry, Rosenzweig observed that no form of psychotherapy or healing is without cures to its credit. Concluding that success is therefore not a reliable guide to the validity of a theory, he suggested that some potent implicit common factors, perhaps more important than the methods purposely employed, explained the uniformity of success of seemingly diverse methods. Rosenzweig summarized these common factors in addition to the therapeutic relationship: (1) the operation of implicit, unverbalized factors, such as catharsis, and the yet undefined effect of the personality of the good therapist; (2) the formal consistency of the therapeutic ideology as a basis for reintegration; (3) the alternative formulation of psychological events and the interdependence of personality organization as concepts which reduce the effectual importance of mooted differences between one form of psychotherapy and another (p. 415).
On August 9, 2004, Saul Rosenzweig died at the age of 97. Rosenzweig’s prolific accomplishments, over 225 publications, are notable in surprisingly varied contexts: his seminal discussion of experimenter bias (Rosenzweig, 1933), the correspondence with Freud (Rosenzweig, 1985), the Picture-Frustration Study (Rosenzweig, 1976), his response to Eysenck’s (1952) critique of psychotherapy (Rosenzweig, 1954), and his New York Times acclaimed analysis of Freud’s visit to the US (Rosenzweig, 1992). And of course, germane here, he published the first known proposal for the common factors in 1936 at the ripe old age of 29.
I invite you to read Rosenzweig’s seminal contribution so that you may experience firsthand how far four journal pages can reach—laying the groundwork for common factors and predicting perhaps the most replicated finding in all of psychotherapy, the dodo verdict. Also, check out my interview of him that sheds light on his sources of inspiration for both the common factors and the first invocation of the dodo bird. His first person account of the historical context—where and how the common factors journey started—enables readers to more fully appreciate where we are now:
I think it important to remember where ideas come from and to credit those whose shoulders we now stand. In fact, I believed this to be so important that I persevered against majority opinion to include a tribute to Saul in the prologue of the new edition of the 2010 Edition of the Heart and Soul of Change. His contribution warranted that at the very least.
I had the great privilege to spend some time with Saul on several occasions and he was a pure delight, witty and still quite active in his work. My interview of him for the Journal of Psychotherapy Integration is one of the high points of my career. So that you might enjoy a flavor of what he was like, check out the video of when Saul was presented the Heart and Soul award back in 2002: https://www.youtube.com/user/barrylduncan