Among contemporary political theorists in the West, the idea of individual liberty is generally defined in negative terms as absence of interference. In this lecture, Quentin Skinner argues that if the concept is instead approached genealogically, this orthodoxy begins to appear in need of qualification and perhaps abandonment. Because the concept of interference is such a complex one, there has been much dispute even within the liberal tradition about the conditions under which it may be legitimate to claim that freedom has been infringed. Skinner is chiefly concerned, however, with the many political theorists who have wished to challenge the core liberal assumption that freedom is best understood as absence of interference. Some doubt whether freedom is best defined as an absence at all, and instead attempt to connect the idea with specific patterns of moral behaviour. Other critics, meanwhile, agree that the presence of freedom is best understood as the absence of something, while arguing that freedom fundamentally consists in the absence not of acts of interference but rather of broader conditions of arbitrary domination and dependence.