the continuity argument
I have already suggested that the impetus for Freud's adoption of the concept of unconscious mental events was provided by his clinical work. It was difficult for Freud to accommodate his clinical observations and inferences within a psychology of consciousness. However, such a transition could not be philosophically innocent. Even as an essentially explanatory concept, the idea of "the unconscious' might have been formulated along the lines of the dissociative or dispositional models within the framework of dualism. Freud chose the more radical philosophical path of nesting his theory within a materialist conception of mind-brain identity, a conception that contravened intuitions that were widely shared during his lifetime.
Smith, D.L. (1999). Justification: the continuity argument, in Freud's philosophy of the unconscious, Dordrecht, Springer, pp. 59-70.
This document is unfortunately not available for download at the moment.