Our practices of holding people morally and legally responsible for what they do rests on causal relationships between our mental states and our actions – a desire for revenge or a fear for one’s safety may cause a violent act. In either case, John Campbell argues, there is a psychological causal process that leads from the motivating mental state to the action. In Causation in Psychology (Harvard University Press, 2020), Campbell – who is professor of philosophy at the University of California, Berkeley, claims that the existence of such singular causal relations and our knowledge of them do not depend on the existence of psychological generalizations under which they might be subsumed. Moreover, imaginative understanding or empathy enables us to trace these one-off, idiosyncratic causal sequences and thereby attain knowledge of these singular psychological causal relations. Campbell uses his analysis to distinguish human freedom of action at the level of causal process and to provide a new perspective on the traditional mind-body problem.