summaryThis paper argues that an epistemological duality between mind/brain and an external world is an uncritically held working assumption in recent computational models of cognition. In fact, epistemological dualism (ED) largely drives computational models of mentality and representation: An assumption regarding an external world of perceptual objects and distal stimuli requires the sort of mind/brain capable of representing and inferring true accounts of such objects. Hence we have two distinct ontologies, one denoting external world objects, the other cognitive events and neural transformations. A basic question is then raised and explored: If the elements of these two different ontologies are so radically different, how can the one access the other?The last part of the paper sketches an alternative toEDand the associated two ontologies account. Instead of external world objects being construed as independent givens, initiating perceptual processes, they are rather interpreted as ‘computational constructs’. It is argued at length that this account is far more consistent with recent computational models of mind/brain than the two ontologies model associated withED. It is further claimed that an ontology of cognitive and neural states, as well as an external world ontology, have no other epistemic status that as contingent working hypotheses. As such, both ontologies are in principle amenable to revision as evidence, explanatory models, and scientific practices mutually readjust and redefine one another over t