We are happy to announce a talk by Bartosz Więckowski (GU Frankfurt) at the Semantics Colloquium.

Please register beforehand (s.walter@em.uni-frankfurt.de) to receive the access data to zoom on Thursday shortly before the talk starts.

Title: Counterfactual implication and counterfactual possibility

Date: June 10

Time: 2 pm – 4 pm ct


Counterfactual inference is usually studied in terms of proof systems defined on the basis of a model-theoretic semantics (e.g., similarity semantics). Typically, the systems extend classical logic. In this talk, I shall (continue to) motivate and outline an intuitionistic proof-theoretic approach that aims to explain the logic and semantics of counterfactuals directly in terms of suitably defined rules of inference.  I will first present elementary intuitionistic subatomic natural deduction systems which make use of various modes of making assumptions. The systems admit a formulation of a proof-theoretic semantics for elementary would-counterfactuals that is based on normalization. I will then extend these systems with possibility operators which are sensitive to assumption-modes, and consider, how, in the intuitionistic setting (no interdefinability), might-counterfactuals can be suitably defined in terms of would-counterfactuals and mode-sensitive possibility. The systems are sufficient to cover elementary inferences with so-called counteridenticals (e.g., ‘If Superman had not been Clark Kent, Superman would [might] not have been Superman’). Specifically, the proof-theoretic semantics based on the systems does not make use of semantic ontology (e.g., impossible worlds).