This study of Heinz Hartmann's contributions emphasises change within continuity. Specifically, it is argued that he both integrated and changed significantly Freud's structural theory--his 'ego psychology'. This he did through his then-modern concept of adaptation. In turn, adaptation paved the way towards further change in the direction of current emphases on dialogue and intersubjectivity. These new developments have contributed beneficially to theory and clinical practice, but, like all new developments, they have introduced new problems, among them unreflective and undisciplined eclecticism. Consideration is given to the incompleteness inherent in theory construction. In psychoanalysis, the new, object-related developments require as a complement some version of the type of structural theorising initiated by Freud and developed to its highest point by Hartmann and his close collaborators particularly; in meeting that requirement, some version of an objectivist stance is also required to complement the subjectivism and pluralism of the newer developments. Throughout this appreciation of Hartmann's role in the history of psychoanalytic thought, an effort is made to undo the negative effects of misreadings that took his ideas on adaptation and ego psychology to mean an endorsement of superficial adjustment or conformity and an overvaluation of conscious mental processes.