In my speech, I intend to criticize the view that the demarcation of public and private law is a matter of a completely arbitrary choice of the researcher. The main goal of the paper will be to convince the listeners that the divisions of law made by various demarcation theories are more similar than it might seem, which argues for distinguishing some of them over the other. In particular, I will raise the argument that if the division into public and private law were to be assumed to be conventional, the final content of such agreements among researchers would largely depend on the structure of the meta-theory of demarcation, i.e. the mutual entanglement of individual demarcation criteria. However, since the condition for the researcher to freely divide into ius publicum and ius privatum is the equal rights of all conventions in theoretical terms, then - in the face of the differences in the demarcation criteria that we find at the meta-theory level - it would not be possible to maintain the conventional nature of the division. This will ultimately lead us to the conclusion that the demarcation of law into public and private - at least to some extent - is a matter of knowledge, and not just an arbitrary declaration of scientists.