Quiggin, J., "Unawareness without the postulate of the excluded middle"

Monday, 22 June 2026

Title: "Unawareness without the postulate of the excluded middle"

Speaker: Professor John Quiggin, Professor of Economics, University of Queensland

Host:  Professor Dr. Phoebe Koundouri, Department of International & European Economic Studies, Athens University of Economics and Business

Room:  76, Patission Str., Antoniadou Wing, 3rd floor, Room A36

Abstract: The question of how to represent unawareness of possibilities relevant to a decision remains problematic despite decades of work on the topic.  The proposed response in this paper is to reject the "postulate of the excluded middle", which states that if a proposition is not true, its negation must be true  The rejection of the excluded middle postulate means that the language may be represented by a Heyting algebra rather than the usual Boolean algebra. The Heyting algebra is not closed under negation, but gives rise to a pseudocomplement. The rejection of the excluded middle allows for more realistic representations of incomplete contracts and financial markets.