When engaging in counterfactual thought, people must imagine changes to the actual state of the world. In this study, participants made counterfactual inferences about a series of causal devices (i.e., they answered questions such as “If component A had not operated, would component B have operated?”) and provided explanations of their reasoning. Participants avoided breaking deterministic causal links (i.e., A always causes B), but were willing to break probabilistic causal links (i.e., A sometimes causes B) to keep prior causal events in the same states as in the actual world. Participants’ explanations of their reasoning were consistent with this pattern of inferences. Our results suggest that people use their explanation of the antecedent event (the “if” clause) to guide their counterfactual inferences. We conclude by discussing the implications of these findings for two rival Bayes-net theories of counterfactual reasoning (Pearl, 2000; Hiddleston, 2005).