This article establishes a sociological theoretical framework that gives sense to the way art museums respond to problems of access and social inclusion. It assumes the theories of differentiation and social exclusion developed by Niklas Luhmann in the broader framework of his theory of social systems. An art museum in Chile was analyzed, based on in-depth interviews with individuals located in different positions in the organization. Confirming previous studies by Paul J. DiMaggio, the article observes that an art museum in Chile has generated internal organizational coalitions, each of which gives meaning to the museum's visitors in a different manner. Applying the theory of social systems, these coalitions are explained by reference to three aspects of a social system of art: a) how it generates a memory of its own, b) how it defines rules for participation, and c) how it is affected by problems of social exclusion that are characteristic of a functionally differentiated society. These coalitions differ from each other with regard to the "patterns of causal attribution" that their members assume when explaining the number of visitors that the museum receives.