Journal of Philosophical Logic

, Volume 41, Issue 2, pp 493–503 | Cite as

Why the Hardest Logic Puzzle Ever Cannot Be Solved in Less than Three Questions

  • Gregory WheelerEmail author
  • Pedro Barahona


Rabern and Rabern (Analysis 68:105–112 2) and Uzquiano (Analysis 70:39–44 4) have each presented increasingly harder versions of ‘the hardest logic puzzle ever’ (Boolos The Harvard Review of Philosophy 6:62–65 1), and each has provided a two-question solution to his predecessor’s puzzle. But Uzquiano’s puzzle is different from the original and different from Rabern and Rabern’s in at least one important respect: it cannot be solved in less than three questions. In this paper we solve Uzquiano’s puzzle in three questions and show why there is no solution in two. Finally, to cement a tradition, we introduce a puzzle of our own.


Boolos Logic puzzle Information theory 


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  1. 1.
    Boolos, G. (1996). The hardest logic puzzle ever. The Harvard Review of Philosophy, 6, 62–65.Google Scholar
  2. 2.
    Rabern, B., & Rabern, L. (2008). A simple solution to the hardest logic puzzle ever. Analysis, 68, 105–112.Google Scholar
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    Roberts, T. S. (2001). Some thoughts about the hardest logic puzzle ever. Journal of Philosophical Logic, 30(4), 609–612.CrossRefGoogle Scholar
  4. 4.
    Uzquiano, G. (2010). How to solve the hardest logic puzzle ever in two questions. Analysis, 70, 39–44.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2011

Authors and Affiliations

  1. 1.CENTRIA - Centre for Artificial IntelligenceThe New University of LisbonLisbonPortugal

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