Joseph J. Sandler, while never proposing any new school of psychoanalysis, is very important because he moved to update and integrate current psychoanalytical theories. Specifically, he moved to transform traditional Freudian drive theory to an object relations theory. According to objects relations theory, we are influenced by relations to the objects around us. Objects can actually be understood to mean any important person or thing that's the object of another person's "feelings or interests" ("Object Relations Theory"). It argues that drives we feel for hunger, sex, fear, or other emotions have objects attached to them. For example, we are never just hungry; we are hungry for something. What Sandler did was examine "the representational world, the concept of safety, feeling states, role responsiveness, internal object relations, projective identification, unconscious fantasy, trauma, the basic psychoanalytical model, and the Hampstead Psychoanalytical Index"--all with the purpose of relating these things to an "object relations model" ("Integration and the Hampstead Index--Joseph J. Sandler 1927-1998").
He is particularly noted for introducing the term actualization into psychoanalysis. His idea was that a psychoanalyst could uncover past object-relationships by playing a different and specific role with each patient, a technique he called "role responsiveness" in which the psychoanalyst became "someone a little different with each patient" ("Joseph J. Sandler").
Joseph J. Sandler was very important because he tried to advance and integrate modern psychoanalytic theories and moved the traditional theories of Freud to an object relations theory. By this theory, we are influenced by relations regarding what is around us regarding a person's feelings.