The illusion of reality: how (not) to think of hallucination
Phenomenology and the Cognitive Sciences June 20, 2026 Søren Overgaard, Laura Oppi, Kasper Møller Nielsen et al.
Defining hallucination is surprisingly difficult: most definitions either miss cases that clinicians consider hallucinations or include cases they do not. This paper first shows why existing accounts fail, then develops a new definition that captures all and only the cases clinicians classify as hallucinations. The key is clarifying two often vague ideas: that hallucinations have a 'sense of reality' and that they are 'perception-like'. By specifying exactly what these mean, the authors provide an account that matches clinical usage.