The customary distinction between dispositional and categorical properties is critically examined, and replaced by one between dispositional and occurrent predication. The ontological ground of the latter distinction is explained using the framework of the four-category ontology. An account is sketched of the ontological status of laws of nature, and its similarities to and differences from D. M. Armstrong’s account are discussed, particularly the key role in the new account of the categorial distinction between substantial and non-substantial universals. A theory of natural powers is advanced and contrasted with the recent theories of C. B. Martin and George Molnar.