Theories of counterfactuals agree on appealing to a relation of comparative similarity, but disagree on the quantificational force of counterfactuals. We report on two experiments testing the predictions of three main approaches: universal theories, homogeneity theories, and single-world selection theories (plus supervaluations over selection functions). The critical cases in our experiment were constructed so as to discriminate between the three theories. Our results provide empirical support

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... or the selectional theories, while challenging the other two approaches.