This dissertation examines the practice of categorizing works of art and its relationship to art criticism. How a work of art is categorized influences how it is appreciated and criticized. Being frightening is a merit for horror, but a demerit for lullabies. The brushstrokes in Monet's "Impression, Sunrise" (1874) look crude when seen as a Neoclassical painting, but graceful when seen as an Impressionist painting. Many of the judgments we make about artworks are category-dependent in this way, but previous research (...) has rarely examined in depth the ontological structure of art categories, how they are generated and maintained, and how they function. This dissertation fills this gap. The proposal of this dissertation can be summarized as follows. Categories (especially genres) should be analyzed as clusters of rules that regulate the responses and behaviors of agents in the artworld. The visual mundaneness is a critical reason to consider Duchamp's "Comb" (1916) provocative, given the existence of the readymade as a set of rules that justifies such reasoning. The critical and appreciative practice of which categorization is a part is a social practice of making, declaring, proposing, reforming, and developing rules of appreciation. How we appreciate artworks, and how criticism guides our appreciation, is sensitive to how we categorize artworks. How we categorize artworks is sensitive to what categories have been set up in our community and which categories are active regarding each artwork. (shrink)