The very notion of “multilateralism” seems straightforward. It immediately suggests an approach of international relations different from the one to which other “ism” notions refer, like “unilateralism,” “bilateralism,” “regionalism,” imperialism,” and “colonialism.” In this respect, “multilateralism” sounds like some kind of good international governance, like an alternative to the absence of a “global state.” Yet, in any endeavor to assess what could be “the future” of multilateralism, it is worth trying to better approach the notion, as it is understood in the international legal world.