Research Group
in Analytic Philosophy

Abstract

The method of thought experiments pops up in Counterfactuals, section 3.2. Lewis considers the idea that the assertable [acceptable in our terminology] counterfactuals are those whose consequent follows from the supposition of the antecedent, together with further unstated premises thought to be cotenable with it. We find a simple counterfactual acceptable, it is argued, to the extent that (i) our probability of the consequent under the thought experiment of counterfactually supposing the antecedent is high, (ii) provided the latter is on-topic with respect to the former. Counterfactual supposition is represented by Lewisian imaging. Topicality, by an algebra of subject matters together with a topic expansion/topological closure operator. A topic-sensitive probabilistic logic is then provided, to reason about the acceptability of simple counterfactuals.