On the face of it, this might seem a somewhat frivolous, not to say over-familiar, title for an essay on the influence of Charles Beitz's Political Theory and International Relations (hereafter, PTIR); Beitz, however, will recognise the implicit comparison between his work and John Rawls's A Theory of Justice, and will accordingly, I hope, forgive the familiarity. But, accepting that this is a title that conveys respect, it might still be argued to be inappropriate on the rather different grounds that it substantially overstates the influence of PTIR. Can it really be the case that this relatively short (under 200 pages) volume with an over-ambitious title ‘changed the subject’ in the way that A Theory of Justice certainly did a few years earlier? Obviously the subject in question – international political theory – is rather more limited than the whole world of at least Anglo-American political theory that was changed by Rawls's work, but such a claim can, I think, be defended.