2 Private and Public Law
After the Introduction comes the body of Private Law as opposed to that of Public Law. By general consent this Roman distinction between jus privatum and jus publicum is accepted as the most fundamental division of the corpus juris. Public law comprises the rules which specially relate to the structure, powers, rights, and activities of the state. Private law includes all the residue of legal principles. It comprises all those rules which specially concern the subjects of the state in their relations to each other, together with those rules which are common to the state and its subjects. In many of its actions and relations the state stands on the same level as its subjects, and submits itself to the ordinary principles of private law. It owns land and chattels, makes contracts, employs agents and servants, and enters into various forms of commercial undertaking; and in respect of all these matters it differs little in its juridical position from its own subjects. Public law, therefore, is not the whole of the law that is applicable to the state and to its relations with its subjects, but only those parts of it which are different from the private law concerning the subjects of the state and their relations to each other. For this reason private law precedes public in the order of exposition. The latter presupposes a knowledge of the former.
The two divisions of public law are constitutional and administrative law. It is impossible, however, to draw any rigid fine between these two, for they differ merely in the degree of importance pertaining to their subject-matters. Constitutional law deals with the structure, powers, and functions of the supreme power in the state, together with those of all the more important of the subordinate departments of government. Administrative law, on the other hand, is concerned with the multitudinous forms and instruments in and through which the lower ranges of governmental activity manifest themselves.