Theories of institutions have become very popular in the social sciences. Thus, we often encounter the claim “Institutions Matter” in the new literature, which is called “institutionalism”. It is time to make a critique of this theme, asking what an institution is and what it “matters” for. “Institution” stands for two very different sorts of entities in social reality—rules and organisations—and the new institutionalism comes in two corresponding versions, economic or atomistic neo-institutionalism against sociological or holistic neoinstitutionalism. The notion of new logic of individual behaviour—a logic of appropriateness—is flawed, as it is not in agreement with basic notions in the philosophy of action.