This valuable paper deals with a crucial issue, the validation of psychoanalytic data and theory. Five categories of psychoanalytic propositions are distinguished: 1, observable patterns of overt behavior; 2, material derived introspectively;

3, unobservable, inferable unconscious processes, based on empirical data; 4, those pertaining to psychoanalytic theory; 5, psychoanalysis as a treatment method.

Not all levels of psychoanalytic theory can be validated in the same way; certain aspects of psychoanalytic theory defy empirical validation but are tested more effectively by their inner consistency and continued usefulness in explaining empirical data. Psychoanalytic principles have been gradually evolving and are subject to change as the necessity arises to explain new data. New research techniques are needed to better evaluate various aspects of the treatment method including therapeutic successes and failure.