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Philosophy

The Logic of Counterfactual Conditionals

Quick fact

Counterfactual conditionals are often called 'contrary-to-fact conditionals' because they describe situations that are contrary to what actually happened. David Lewis's 1973 book 'Counterfactuals' developed the most influential semantic theory for them, using the idea of 'possible worlds'.

Why this is interesting

We use 'what-if' statements every day: 'If I had left earlier, I wouldn't have missed the train.' But did you know that the logic behind these statements is famously tricky and philosophically rich?