The core idea of sovereignty is that of the ultimate source of political authority within a realms. This is the power that monarchs claimed in their battles against lords and princes on the one hand and popes on the other. Their realms (or kingdom) was theirs, and their authority over it was to be shared with no one The core notion of sovereignty – the ultimate source of political authority within a realms- requires unpacking. Sovereignty is associated with modern kingdoms and states ; the ‘realms’ in question are the well-defined territories of such states. The relevant notions of political authority is more controversial. Something is an authority in the sense relevant here, only if its directives are (and are intended to be) action-guiding. For instance, consider the law. It forbids us from doing certain things, and it intends these prohibitions to guide our behaviour , specifically, these prohibition are reason-providing. Authorities, then , mean to guide behaviour by providing reasons for action to their subject. On this view, political authority is not to be understood simply as justified force ; something is a genuine authority only in so far as its directives are reasons for action. Sanctions or force may frequently be necessary as a means to make effective this authority , but the two are not to be conflated.