In his study, F. Ancora is exploring the fundamental concepts of jurisprudence: the rule of law, the state of law and the concept of legal certainty. This analysis proves – according to its author – that the aforementioned concepts evolve and that they are completely unchangeable in their content. F. Ancora considers this feature to be not only important, but also desirable. It makes it possible to adopt the content of basic legal categories into changing social, economical and political conditions, even if it may threaten legal certainty.