This chapter presents that the evidence is in Ehrlich's Fundamental Principles of the Sociology of Law as the reprint of the translation done in 1936. Ehrlich's distinctive observations had an impact on lawyers, especially the legal realists in the United States and Scandinavia in the thirties, legal anthropologists since the forties, and legal educators and sociologists of law in the seventies and eighties. Ehrlich's notion of sociological jurisprudence as legal science demonstrates that he is fully aware of the highly invasive nature of modern law, especially of state law and that he recognizes this as the result of a historical process of the differentiation of legal practice. Ehrlich's critical view of the state and state law is a direct consequence of his sociological observations of the evolutionary development of modern law. Sociology was the cornerstone of Ehrlich's project to reform and revitalize jurisprudence.