A theory of categorization is presented in which knowledge of causal relationships between category features is represented as a Bayesian network. Referred to as causal-wodel theory. this theory predicts that objects are classified as category members to the extent they are likely to have been produced by a categorysJ causal model. On this view, people have models of the world that lead them to expect a certain distribution of features in category members (e.g.. correlations between feature pairs that are directly connected by causal relationships), and consider exemplars good category members when they manifest those expectations. These expectations include sensitivity to higher-order feature interactions that emerge from the asymmetries inherent in causal relationships.