A generation ago, Imre Lakatos (1970) expounded a theory of scientific progress in the natural sciences. Whether he meant his theory to apply to social science or not, it can be employed to help social scientists understand whether their own research programs are progressive. Theories of international relations may never meet Lakatos' rigorous standards, but his criteria for progressiveness provide "clear and sensible criteria for the evaluation of scientific traditions" (Keohane 1983/1986: 161). As other essays for this conference have detailed, Lakatos argued that theories are embedded in research programs, which contain inviolable assumptions (the "negative heuristic," or "hard core"), along with observational hypotheses and scope conditions. Research programs also contain positive heuristics—which suggest to scientists what sorts of hypotheses to pursue.