Alasdair Urquhart

Alasdair Ian Fenton Urquhart (/ˈæləsdər ˈɜːrkərt/; born 20 December 1945) is an emeritus Professor of Philosophy at the University of Toronto. He has made contributions to the field of logic, especially non-classical logic. One of his ideas is proving the undecidability of the relevance logic R. He also published papers in 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.