New in paperback. Hardcover was published in 2021. The past few decades have seen an explosion of research on causal reasoning in philosophy, computer science, and statistics, as well as descriptive research in psychology about how people reason about causes. This book integrates these lines of research and argues for an understanding of how each can inform the other: normative ideas can suggest interesting experiments, while descriptive results can suggest important normative concepts. Woodward's overall framework builds on an interventionist treatment of causation, and discusses proposals about the role of invariant or stable relationships in successful causal reasoning and the notion of proportionality. He argues that these normative ideas are reflected in the causal judgments that people actually make as a descriptive matter.