  Tropes provide an elegant and economical base for an ontology. Unlike almost all competing ontologies, that of Williams rests on just one basic category, which can be used in the construction not just of things and their properties and relations, but of further categories, such as events and processes. Events are replacements of the tropes that are to be found in a given location. Processes are sequences of such changes. Trope theory is well placed to furnish an attractive analysis of causality, as involving power tropes that govern and drive the transformations to be found in events and processes.