Kinds of architectural ontologies. Architecture’s distinctive qualities may help sort among candidate ontologies. One option is concretism, which—in keeping with standard causal efficacy claims and expressed intentions of architects, clients, and users—suggests that architectural objects are either built structures or, on one variant, otherwise physically instantiated designs for such structures (such as models). Concretism is supported by an artifactual ontology that subsumes architectural objects into the class of objects that are the product of intentions, designs, and choices (on the view that all art objects are best so understood, see Dutton 1979, S. Davies 1991, Thomasson 1999, and Levinson 2007.) One version of architectural artifactualism identifies buildings as systems (Handler 1970). As against concretism, intentionality may be the mark of materially constituted, designed architectural objects but that need not commit us to their existence alone or their primacy among such objects. Moreover, taking intentions as determinative leaves the concretist with the problem of shifting intentions and unintended goals attached to built structures over time.