In comparison to other questions related to nationalism (for example, is nationalism more a pre-modern or modern phenomenon? Is it more of a political or ethno-cultural nature?), relatively little attention has been devoted to the question of whether nationalism is more rational or irrational. Weber's definition of instrumentally rational and value-rational action has been used in this analysis to determine to what extent nationalism is rational or irrational. The analysis has focused mainly on those concepts of nationalism and those phenomena associated with nationalism that are predominantly irrational or extra-rational. Some psychological and anthropological constants constitute the irrational (extra-rational) side of nationalism. Nationalism as a Janus-faced phenomenon comprises the irrational (extra-rational) and the rational. The rational and irrational overlap quite profoundly in numerous manifestations of nationalist behaviour.