The last thirty years has seen the growth – or, as I should prefer to say, rebirth – of a field of inquiry that for much of the twentieth century was quiescent. That field would now routinely be called international political theory, in part to distinguish it from both political theory in general and International Relations (IR) theory in general, though of course, there are overlaps with both. Roughly speaking that field consists in ethical, historical and philosophical reflection on the manner and matter of international politics. There is a rich body of such inquiries in intellectual history (and not just in Europe) but for a variety of historical and intellectual reasons such inquiries had fallen out of fashion by the late nineteenth century. This situation was reinforced by the simultaneous evolution of the individual disciplines of political science and IR, and in particular by the rise of methodological and epistemological claims in both largely inimical to those earlier sorts of inquiry. Thus, as the story is widely told, ‘political theory’ and ‘IR’, as academic inquiries, followed largely independent paths for most of the twentieth century.