Abstract Analytical political philosophy is a complement to social science. Whereas social scientists aim to determine the empirical facts about human behaviour and institutions, political philosophers aim to determine what ought to be done in light of that information. How should states be organized? What kinds of projects should they pursue? Are there some actions that are impermissible? No set of empirical facts can dictate the answers to these kinds of questions. You could pile up a mountain of data about the differences between, say, democracies and dictatorships, but without the normative element that is the political philosopher’s concern, nothing would follow about which form of government ought to be implemented.