Problem setting. Different directions of modern science of international law explore the problem of the existence of its subject, its typology, forms of attitude to the law of na- tional states, etc. In this article, asking about the very possibility of international law, the focus on the subject area is shifted to a methodological one. This, perhaps, is the rare case when a “study of investigators” brings an unconditional benefit to understanding the essence of the cognizable subject. The article concludes that the special form of dialectics found in the movement of these methodologies reflects how the phenomenon of interna- tional law actually realizes itself. German classical philosophy titled this form as a “reflection of essence”.Recent research and publications analysis. The methodological dualism of the theo- ry of international law reflects in methodological monism. The monistic theory of interna- tional law, in its turn, “splits” into adherents of the primacy of the national state, on the one hand, and on the other, those who insist on the superiority of international law.Paper main body. Rational cognition, incapable of thinking the contradictions objec- tively existing in the subject, is horrified by such “strange behavior” of international law. It even goes so far that the very fact of its existence is being questioned. The article uses the experience of I. Kant’s transcendental philosophy, which first criticized such knowledge. With his question: “How is a priori synthesis possible?”, He showed an example of how reasonable knowledge is possible, capable of thinking the dialectic of opposites in its subject matter.This study can serve as another contribution to the newly emerging science of the philosophy of international law. Sources in the current literature on this issue, unfortu- nately, do not affect the problem of knowing its contradictory nature.