Abstract

In this paper, we present new cases of illusion and hallucination that have not heretofore been identified. We argue that such cases show that the traditional accounts of illusion and hallucination are incorrect because they do not identify all of the cases of non-veridical experience that they need to and they elide important differences between cases. In light of this, we present new and exhaustive definitions of illusion and hallucination. First, we explicate the traditional accounts of illusion and hallucination. We then proceed to outline cases of pure property experience—that is, experience as of properties, but not as of objects. We suggest that some might find it to be plausible that olfactory experience is of this kind. We argue that, within instances of such pure property experience, one can identify cases of veridical property perception, illusory property perception and hallucinatory property experience. With these distinctions in hand, we re-examine ordinary cases of experiences as of objects having properties. Drawing on the ideas uncovered by considering pure property experience, we bring to light many new cases of illusion and hallucination within ordinary experience as of objects having properties. These consist in different combinations of veridical perception, illusory perception and hallucination of both objects and properties. In order to accept that these new cases of illusion and hallucination exist in ordinary experience as of objects having properties, nothing turns on accepting the idea that there is pure property experience, or that olfactory experience is an instance of it. Such a conception of experience is simply a tool—a ladder to gain a good vantage point from which one can appreciate that there are these further cases. But this is a ladder that, as Wittgenstein might say, can be thrown away once it is used. Identifying new instances of illusion and hallucination provides much needed, important data for testing theories of experience and perception—theories that are frequently motivated, and should be judged, by their ability to account for cases of illusion and hallucination.