Immanuel Kant 
The Science of Right 

From the introduction: ‘The Science of Right has for its object the principles of all the laws which it is possible to promulgate by external legislation. Where there is such a legislation, it becomes, in actual application to it, a system of positive right and law; and he who is versed in the knowledge of this system is called a jurist or jurisconsult (jurisconsultus). A practical jurisconsult (jurisperitus), or a professional lawyer, is one who is skilled in the knowledge of positive external laws, and who can apply them to cases that may occur in experience. Such practical knowledge of positive right, and law, may be regarded as belonging to jurisprudence (jurisprudentia) in the original sense of the term. But the theoretical knowledge of right and law in principle, as distinguished from positive laws and empirical cases, belongs to the pure science of right (jurisscientia). The science of right thus designates the philosophical and systematic knowledge of the principles of natural right. And it is from this science that the immutable principles of all positive legislation must be derived by practical jurists and lawgivers.’