Although most attempts to foster interdisciplinary dialogue are located outside mainstream International Relations (IR), this article seeks to problematize how the two dominant paradigms of IR theory, realism and liberalism, think historically. The argument proceeds by examining how the disciplines consider what historical knowledge is useful for, that is, how they think historically or are historically conscious. This constitutes a shift away from the dominant dialogue over how to ‘do history’ in IR. Historical consciousness is defined as the understanding of the temporality of historical experience or how past, present and future are thought to be connected. The analysis is set up to explore the extent to which both disciplines share a similar historical consciousness beyond merely treating history as instructive. To do so the article first examines the canon of European historiography to identify three genres of historical consciousness: history as teacher, history as narrative, history as representation. This survey of pre-positivist historiography serves to show the complexity of historical reflection within that discipline, something against which variance within IR theory can also be compared. Disciplinary comparison reveals that three genres of historical consciousness are present in liberalism and realism: lessons of history, revenge of history, and among progressive realists a speculative escape from history genre. Whereas lessons of history spans both ‘isms’ in IR, realism is shown to have a more complex understanding of temporality, thereby providing another conceptual starting point for distinguishing between these two ‘traditions’. Moreover, these differences between genres of historical consciousness used within realism capture the split between realists that lies not in the origin of anarchy itself but in how realists think historically. What emerges, therefore, by comparing how disciplines think historically rather than ‘do’ History, is the equally purposive or even political use of the historical knowledge they produce.