title: The Construction of Impossibility: A Logic-Based Analysis of Conjuring Tricks.
abstract: Psychologists and cognitive scientists have long drawn insights and evidence from stage magic about human perceptual and attentional errors. We present a complementary analysis of conjuring tricks that seeks to understand the experience of impossibility that they produce. Our account is first motivated by insights about the constructional aspects of conjuring drawn from magicians' instructional texts. A view is then presented of the logical nature of impossibility as an unresolvable contradiction between a perception-supported belief about a situation and a memory-supported expectation. We argue that this condition of impossibility is constructed not simply through misperceptions and misattentions, but rather it is an outcome of a trick's whole structure of events. This structure is conceptualized as two parallel event sequences: an effect sequence that the spectator is intended to believe; and a method sequence that the magician understands as happening. We illustrate the value of this approach through an analysis of a simple close-up trick, Martin Gardner's Turnabout. A formalism called propositional dynamic logic is used to describe some of its logical aspects. This elucidates the nature and importance of the relationship between a trick's effect sequence and its method sequence, characterized by the careful arrangement of four evidence relationships: similarity, perceptual equivalence, structural equivalence, and congruence. The analysis further identifies two characteristics of magical apparatus that enable the construction of apparent impossibility: substitutable elements and stable occlusion.
authors.affiliation: Department of Computing and Information Systems, The University of Melbourne Melbourne, VIC, Australia.
authors.forename: Wally
authors.initials: W
authors.lastname: Smith
authors.affiliation: Department of Information and Computing Sciences, Universiteit Utrecht Utrecht, Netherlands.
authors.forename: Frank
authors.initials: F
authors.lastname: Dignum
authors.affiliation: Department of Computing and Information Systems, The University of Melbourne Melbourne, VIC, Australia.
authors.forename: Liz
authors.initials: L
authors.lastname: Sonenberg
keywords: conjuring; impossibility; propositional logic; stage magic