Although physicalism is usually understood as an ontological thesis, it is not clear that what implications this position has on the matter of ontology expressed by the question “What there is?” In this paper, I begin with Quine's “indispensability argument,” and abstract from it a framework for sorting ontological positions. Then, I try to locate supervenience thesis, which is an important part of physicalism, within the framework above. One conclusion of this paper is that supervenience thesis works, neither as a direct assertion on what there is nor as an assertion on the criterion of ontological commitment we should adopt, but as an assertion on the class of the sentences from which we should extract ontology.