Inequality is the defining issue of our time. Yet in part because it has become so central to contemporary politics, exactly what inequality “is” often gets assumed rather than asked. The end result sometimes generates more heat than light. This is a serious problem in an era when the most pressing challenges before us, be it climate change or international migration, can only be solved to the extent we also reckon effectively with the inequality in which they are set. In this lecture, rather than ask how political thought can illuminate inequality, I shall therefore take the opposite approach, and explore some of the ways in which inequality illuminates the history of political thought. To do this I will examine how global inequality has been understood in different times and different places, and end with the question: whose inequality gets to count?