Matthew Nudds "Naïve Realism and Hallucinations"

The so-called ‘reverse causal argument’ shows that there is a kind of  event that is common to perception and hallucination: that although a  perceptual experience may be an event of a kind that could not occur  when hallucinating, it is an event that also belongs to the same psychological kind as a causally matching hallucination. This  presents the following problem for the disjunctivist: if it is  possible to give some characterisation of the nature of the  psychological kind to which hallucinatory experiences belong, then  the occurrence of an event of that kind explains the phenomenal  character of veridical perception better than the naïve realist  features of the experience. The character of the hallucinatory experience ‘screens-off’ the naïve realist character, and so  undermines the disjunctivist’s claim that naïve realism provides the best account of the nature of our visual experience.

The naïve realist's response is to give an ‘epistemic’ account of the  nature of hallucinations: all that can be said about the phenomenal character of hallucinations is that they are experiences that are indiscriminable from veridical perceptions. This response has been criticised on the grounds that the disjunctivist appears committed to denying that hallucinatory experiences have a sensory character at all: that, in effect, they can say no more about a hallucination than that it is the absence of experience together with the subject’s ignorance of this absence (Smith). If that is all that can be said, then the subject of a hallucination is in no better position than the philosophical zombie, and we are left unable to explain, e.g., how someone could come to know anything positive about their hallucinatory experiences (Seigel).

This paper attempts a diagnosis: I examine in detail the screening-off argument in order to determine what the disjunctivist is committed to denying about the nature of hallucinatory experiences, and why. I then ask whether they can avoid the claim that hallucinations lack sensory character and whether they can give some account of how we can have positive knowledge of our hallucinatory experiences. In doing this I attempt to locate what is it at issue between the disjunctivist and those who claim that perceptual experiences belong to the same fundamental psychological kind as hallucinatory experiences.