Alasdair Urquhart at the Association of Symbolic Logic, Pittsburgh, May 2004
Alasdair Ian Fenton Urquhart, born 20 December 1945, is an emeritus Professor of Philosophy at the University of Toronto. He has made notable contributions to the field of logic, especially non-classical logic. One of his most notable achievements is proving the undecidability of the relevance logic R. He also published numerous papers in major theoretical computer science venues, mostly on mathematical logic topics of relevance to computer science.
A native of Scotland, Urquhart received his MA in Philosophy from the University of Edinburgh in 1967, and his Ph.D. from the University of Pittsburgh in 1973 under the supervision of Alan Ross Anderson and Nuel Belnap.
 Selected publications
- "The Undecidability of Entailment and Relevant Implication." Journal of Symbolic Logic 49(4): 1059-1073 (1984).
- with Stephen A. Cook, "Functional Interpretations of Feasibly constructive Arithmetic", Annals of Pure and Applied Logic, 1993; preliminary version at STOC'89
- "The Complexity of Decision Procedures in Relevance Logic II", J. Symbolic Logic, Volume 64, Issue 4 (1999), 1774-1802.
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