The essay has two main aims: (a) to provide an explanation of the ontology on which is based the concept of the “art world”; and, on the basis of that account, (b) to inquire whether the so-called Institutional Theories of Art are well founded. I will argue that it is not possible to consider the art world as a social institution and that, because of this, the so-called Institutional Theories of Art lack a secure foundation.