Having defended the significance of empirical studies, I now want to elaborate on the different functions that might have in political philosophy. I will make use of Adam Swift’s distinction of three different roles sociological studies of normative beliefs might have for philosophical theories of justice (Swift et al.1995, 18ff.; Swift 1999, 349ff.; 2003, 15ff.). Although this is, of course, a specific topic of political philosophy and a particular area of empirical, it will still be a valuable starting point for the debate about empirical data’s functions more generally.