Assessing ‘progress’ in the scientific study of international politics faces several difficulties. There is initially the issue of the objects of study and how the subject matter shall be delineated. Subsequently, there is the issue of the criteria by which we can produce warranted knowledge. One position argues that true knowledge can only be gained by following a particular method. Popular since Descartes, this stance is nowadays best represented by the unity of science position whereby anything claiming to have scientific status has to follow a specified method. An alternative contention proposes that, first of all, ‘knowledge’ should not simply be identified with one mode of knowing, particularly since even within science there exist many different warrants that cannot be reduced to one criterion.