This paper aims to analyse the philosophical premises on which the idea of unity of law (identity of legal system) is based. In the history of legal philosophy this idea found its main arguments in the presumption of totality of legal regulation. Such totality translated the philosophical tenets of holism according to which law is not limited to the positive-law rules and institutes, and transcends to the supreme values priming over the legal instruments human beings and collectives create for regulation of their mutual behavior. This argument implies one of the highest values (that of justice) under which all the social relations can be subsumed and which finally gives the binding force to positive law. The author argues that this line of thought is based on philosophical objectivism and naturalism, and can easily lead to primacy of the social over the individual. To substantiate the idea of systemacity of law, one can turn to the modern debates about logic of social cohesion (Searle) and construct a legal system identity as a purely intellectual hypothesis necessary for thinking about law. In the terms of Foucaultâ€™s analysis of power relations, this integrity can be described as a unity of discourse, or as a unity of societal practices, as proposed by Kuhn. This reconstruction of integrity of law can be extended by appealing to the basic ideas of normative philosophy of law (from Hart and Kelsen to Raz and Marmor) and is reconcilable with the conception of normative systems of Bulygin-Alchourron.