F rom the moment he became a consultant to Bateson's team in early 1954, Don Jackson brought his understanding of Harry Stack Sullivan's Interpersonal Theory of Human Behavior into the project. Prior to joining the Bateson project, Jackson spent four years, from 1947 through mid-1951, studying with Sullivan and his multidisciplinary team at Chestnut Lodge in Rockville, Maryland, and at the Washington School of Psychiatry. Sullivan and colleagues (prominent social scientists of that day, including Frieda Fromm-Reichmann, Erik Erikson, Karin Horney, Edward Sapir, Claire Thompson, and Harold Lasswell) offered an alternative definition of psychiatry as &quotthe study of processes that involve or go on between people" the field of interpersonal relations, under any and all circumstances in which these relations exist &quotit seems a personality can never be isolated from the complex of interpersonal relations in which the person lives and has his being" (Sullivan, 1945, p. 4-5). Sullivan acknowledged having been influenced by a number of people; in the fields of neurology and psychiatry, Sigmund Freud, Adolf Meyer, William Alanson White, while his primary philosophical/ intellectual antecedents included George Herbert Mead, Charles Horton Cooley, and physicist P. W. Bridgman.

S ullivan's insistence upon operationalizing his language, his focus upon observable behavior, his dissatisfaction with the capacity of individually oriented language to describe interpersonal phenomena, his recognition of the paramount importance of the client's experiences in living to understanding behavior, the significance he placed on the therapist as a "participant observer" (Sullivan, 1945, p. vi), and his emphasis on the necessity for each individual to adapt to the circumstances [i.e. context] and relationships of which he or she is a part, had a profound and career altering influence on Jackson. In turn, Jackson's grasp of the implications of Sullivan's Interpersonal Theory had an enormous impact on the direction of research conducted by Bateson's team in general, on the thinking of Haley and Weakland in particular, and in the development of the Interactional Approach. (Ray, 1998).