Alasdair Ian Fenton Urquhart (/ˈæləsdər ˈɜːrkərt/ AL-ist-ər UR-kərt; born 20 December 1945) is a Scottish–Canadian philosopher and emeritus professor of philosophy at the University of Toronto.

[3] Amongst his most notable accomplishments is the proof of undecidability of the relevance logic R. He published numerous scientific papers in theoretical computer science venues, mostly on mathematical logic topics of relevance to computer science.

[1][2] He then attended the University of Pittsburgh, receiving an MA and Ph.D. in 1973 under the supervision of Alan Ross Anderson and Nuel Belnap.

[1][2] From 1973 to 1975, Urquhart was an assistant professor at Erindale College, University of Toronto Mississauga.

[2] Starting in 1986, Urquhart was a professor of philosophy at the University of Toronto.