The Epistemic Conception of Hallucination

Disjunctivism about perception is a view about the relation between veridical experiences and hallucinations. Suppose that I see a green cube, and my experience is veridical—no illusion or hallucination is involved.1 The veridical experience, according to disjunctivists, includes as constituents the bit of the world that is perceived and the perceptual relation that the subject bears to it, and these constituents characterize what it is like to see the green cube. The phenomenal character of my veridical experience, they hold, is thus constituted by facts that could not obtain if I were hallucinating. Disjunctivists typically grant that there is a corresponding hallucination in which I could not know just by introspection that I was not veridically seeing a green cube. But they hold that the most basic characterization of what it is like to have such a hallucination—its most basic phenomenal character—must differ from that of the veridical green-cube experience. The main opponents of disjunctivism are common-kind theorists, who hold that the most basic phenomenal character in both experiences is the same. Although the primary commitment of disjunctivism concerns veridical perception, rather than hallucination, disjunctivists aim to respect two central assumptions about hallucination: that they can ‘match’ veridical perceptions, and that they can differ phenomenally from one another. Both assumptions are commonplaces in their own right, and the first is presupposed by the debate between disjunctivism and the common-kind theory. Common-kind theories accommodate both assumptions straightforwardly. ‘Matching’ hallucinations and non-hallucinations share the same most basic sort of phenomenal character, and variation among hallucinations is variation in that same sort of phenomenal character. Disjunctivists, in contrast, cannot