 The debate can be seen as to be centered on preference formation, with rationalist theories (such as neorealism) characterising changes in terms of shifts in capabilities, whereas constructivists focus on preference formation.Rationalists subscribe to positivism, the idea that scientific enquiry must rely upon empirical validation or falsification.Rationalist theories such as neorealism and neoliberalism also have exogeneously given preferences such as can be seen in Kenneth Waltz's "Theory of International Politics", where anarchy is a structural constraint on state behaviour.