The paper addresses the issue of differences in sociological and legal understanding of law, identifies an objective nature of such differentiation, and, at the same time, the need for a minimum conceptual consensus for the development of Sociology of Law (Sociological Jurisprudence). It is shown that such consensus is possible on the basis of studying law as the due and existent, on the basis of a dialectical approach to law, identification of juridical and social aspects in law, examination of the essence of law. The gap between "law in books" and "law in life" can be exploited by means of the frame of references (formal norms (the due) - social institutions (the existent); juridical law - other social law). Such a scheme serves both the interests of sociologists and practical needs of lawyers. The scheme is in compliance with the desire to understand affinity and interdependence of different regulators (social institutions), to identify social aspects of legal activity, the degree of law effectiveness, and interrelations between jurisprudence and other humanities. This scheme can be supplemented by another reference that reflects the degree of achievement of formal equality of subjects in law.