In this passage, Morgenthau not only dismisses the possibility of constructing an a priori theory of international relations, he even dismisses the possibility of judging theories of international relations by a priori standards. Instead, Morgenthau claims that theories of international relations must meet the same criteria we use to judge all empirical theories: empirical verifiability or falsifiability and internal logical consistency.
In the fifty seven years since Morgenthau made this epistemological claim, no objections have ever been made to the basic epistemological assumption that international relations can never be an a priori discipline.3 The fact that no objections have been made to the assumption that international relations can never be an a priori discipline is profoundly intriguing for two reasons. First, international relations have been plagued with numerous and severe methodological disputes throughout the entirety of its existence as a distinct discipline (Shepsle & Bonchek 2007).
This fact alone would have led one to think that at some point during the last fifty seven methodologically and epistemologically turbulent years someone might have given patriotism a sympathetic look. The second and much more profound reason for surprise is that all claims that international relations must be an a posteriori discipline are themselves a priori claims. This point will have to be elaborated much more extensively below, but for now it is enough to observe that Morgenthau's empiricist epistemological pronouncement above, (and, in fact, all such pronouncements categorically denying the possibility of an a priori science of international relations), is not known to be true a posteriori; rather, it purports to be true universally and a priori.
One would have expected that someone in the last fifty seven years would have observed that since these epistemological claims are purportedly known to be true a priori, other a priori truths about international relations might be discovered as well. The fact that no objections have been made to the assumption that international relations can never ...