Publication of The Ego and the Id (1923b), where Freud initially described the tripartite model of id, ego, and superego as the key macrostructures of the mind, ushered ego psychology into psychoanalytic theory. Precursors can be found in Freud's earlier publications: the "Project" of 1895; The Interpretation of Dreams; the metapsychological papers of 1915 on instincts, repression, and the unconscious; and the works on narcissism, mourning, and group psychology.

Freud's book on anxiety (1926d) elaborated the structural theory of ego psychology and played a key role in its evolution. Its new model for symptom formation saw symptoms as arising from compromises among conflicts of the id, ego, and superego. This new formulation of the workings of the mental sphere was introduced as a revision Freud's topographic model, an earlier theory centered on the relationship of mental contents to consciousness. For Freud, the...