Authority figures permeate our daily lives, particularly, our political lives. What makes authority legitimate? The current debates about the legitimacy of authority are characterised by two opposing strategies. The first establish the legitimacy of authority on the basis of the content of the authority’s command. That is, if the content of the commands meet some independent normative standard then they are legitimate. However, there have been many recent criticisms of this strategy which focus on a particular shortcoming – namely, its seeming inability to account for who can legitimately command whom. This is the basis of the second strategy, which attempts to characterize the normative relationship that underlies and makes possible authoritative commands. The central point of Part I is that these two strategies are, in fact, not opposed and both raise questions which a theory of legitimacy must answer. If this is the case, then we need to ask: how ought we to determine the legitimacy both of the content of commands as well as who can command whom? Part II will answer this question. Starting with the question of standing, I argue that we ought not to look for normative principles outside of the institutions in which authority is embedded. Rather, one ought to start by elaborating the ontology of institutions in which a sui generis form of normativity arises. A joint commitment account of social ontology provides the tools necessary to see how the direction obligations emerge concurrently with the formation of institutions. Similarly, the question of content can be answered by paying close attention to the social ontology of institutions. We need not look beyond the internal constitutive standards of the institution itself. The constitutive standards provide an internal criterion by which the legitimacy of commands can be established.