We have rejected verificationism and falsificationism. We have argued instead that objective knowledge arises from a comparison of rival narratives or webs of beliefs. This account of objective knowledge might appear unsatisfactory as a guide on how to deal with the high levels of incommensurability existing between different approaches to political science. If we disagree about the relative merits of narratives, we could look for a common platform – ways of reasoning, standards of evidence and agreed facts – which we could use to compare the narratives. However, different approaches to political science often instantiate rival forms of reasoning that inspire varied standards of evidence and even different concepts of a fact. The nature of objective knowledge is part of what is at issue between them. Does this mean we have no way to decide between different approaches to political science? We will argue it does not. Rather, the several narratives of the history of political science constitute an arena in which to evaluate different approaches to political science.