DISCUSSION: Dr. Heinz Hartmann agreed to the superiority of the structural hypothesis over the topographical, but said it is questionable that one outmodes all aspects of the other. The terms conscious, preconscious, and unconscious were abandoned as mental systems, but retained as descriptive concepts. Also both definitions of preconscious are found in the 1939 Outline, so one was not consistently superseded by the other. The concept that secondary process thinking (derivatives of the unconscious) can be inaccessible to consciousness was a problem Freud struggled with as early as 1915. The inaccuracy inherent in trying to equate unconscious with primary process was known prior to the introduction of the structural hypothesis. Freud suggested that, aside from censorship, these secondary process derivatives might be held in the unconscious by some attraction