The article deals with the problem of certainty of legal cognition in the context of the evolution of Natural Law. It is noted that the category of certainty was understood differently by representatives of various scientific schools and strands of theoretical framework idea. However, the classical doctrines were similar in the sense that certainty is necessary as the initial principle of cognition of legal reality, in contrast to the relativistic post-classical theories, which took the diametrically opposite principle as a methodological basis, namely «uncertainty». The article actualizes the understanding that Nature Law as a classical type of legal understanding has an internal logic of development. It is noted that modern theories of «Resurgence of Natural Law» generally remain within the framework of natural law concepts, but still overcome the dualism and parallelism of the systems of natural and positive law. In ontology, the modern Natural Law recognizes the human construction of law, the participatio