Katalin Farkas "Philosophical Hallucinations and Real Hallucinations"

In philosophical discussions of hallucinations, a hallucination is usually characterised as a perceptual experience which is indistinguishable from a  normal veridical perceptual experience, but whose object doesn’t exist. Macbeth’s experience of  seeing a dagger in front of him is supposed to be an example. It is not always sufficiently emphasised that ‘indistinguishability’ can be used in two different senses. In a ‘metaphysical’ sense, it means exact sameness of phenomenal character of two experiences. In an ‘epistemic’ sense, it means the subject’s inability to tell a hallucinatory experience apart from a veridical experience. This inability may be a result of some cognitive deficiency, rather than of the fact that the experience has the same phenomenal character as a veridical experience. Actual hallucinations belong to this second kind: their subjective character is in fact rather different from those of real experiences, but the subject is prevented from seeing this due to some cognitive deficiency. In this talk, I’ll explore some consequences of this issue with respect to the philosophical notion of hallucination.