Arbor, Michigan. Anomalous Conditional Judgments and Ramsey's Thought Experiment

The Stalnaker/Lewis semantics for counterfactual conditionals is based on a thought experiment proposed by Frank Ramsey. We show that intuitive judgments of the truth of counterfactuals violate predictions derived from the Stalnaker/Lewis semantics. The pattern of violations suggests that the process of counterfactual reasoning follows a different pattern from the process implicit in Ramsey's thought experiment. A counterfactual conditional is a statement of the form, "If P were true, then Q would be true", where P is a proposition that is known to be false, and Q is another proposition. For example, "If Richard Nixon had not resigned from the presidency, he would have been impeached", is a counterfactual conditional. The English philosopher, Frank Ramsey, proposed an influential heuristic analysis of conditional statements which was meant to apply to counterfactuals as well as other forms of conditionals. In general we can say with Mill that 'If p, then q ' means that q is inferrible from p, that is, of course, from p together with certain facts and laws not stated but in some way indicated by the context. (Ramsey, 1931, p.248)