Professor Leon (Lev) Petrazycki contributed significantly to the methodology of law and economics and made Russian legal science famous in Germany with the publication Die Lehre von Eienkommen in 1893 and 1895. The book developed the idea that the influence of legal norms should be evaluated not only from the private view but from the point of national economy. Professor Petrazycki and his students Pitirim Sorokin and George Guins may be ranked among the founders of the economic analysis of law established in 20th century, which was shown earlier in the monograph Pravo i ekonomika (metodologiya) by the author of the paper. The idea of externalism is based on the principle that social and economic factors, i.e. extra scientific make a decisive influence on the development of science. Hence, in studying the history of science, the major task is reconstructing social and cultural conditions (social service) promoting to the development of ideas and theories. The opposite, internalist, approach promotes the idea that science develops only due to inner scientific factors — on the basis of objective logic and of arising and solving economic problems, thanks to the evolution of scholar traditions, create new concepts, solve problems etc. Law has developed two types of argumentation externalist and internalist. Legal positivism calls for the strict adherence to the norms of positive law and excludes other arguments — sociological, economic, moral, historical ones in resolving legal disputes. This is the internalist approach showing the separation of legal space from others (economic, moral etc.). In this regard, the politics of law is something external in terms of law, and the area is intended for politicians. The external type of argumentation allows avoiding extremes and formalism for legal concept. This area of legal science is characterized with open ways of argumentation — sociological and statistical facts, economic rationale, moral arguments. A high idealistic dream of external jurisprudence is in the following: it is necessary to achieve three criteria for legal decisions: legality, efficiency, fairness.