Although ancient ethics used the concepts of property and justice, each of which presupposes something similar to the concept of a right, the concept of a right in the modern sense developed only later. The first philosopher to define a moral right was most likely William of Ockham (c. 1285–1347), who noted that jus sometimes refers to the power to conform to right reason. Thus, he integrated the legal concept of dominium or property into the moral theory that the law of nature determines right action. Hugo Grotius (1583–1645) adopted the resulting theory of natural rights—rights conferred by the law of nature—and made it the basis for his theory of international law. Hobbes and Locke used their conceptions of natural rights to explain the grounds and limits of political obligation. Hobbes (1588–1679) conceives of a right as a liberty of action that is the absence of any contrary obligation...