DIVISION OF THE SUBJECT OF THE ACQUISITION OF THE EXTERNAL MINE AND THINE.

I. In respect of the matter of object of acquisition, I acquire either a corporeal thing (substance), or the performance of something by another (causality), or this other as a person in respect of his state, so far as I have a right to dispose of the same (in a relation of reciprocity with him).

II. In respect of the form or mode of acquisition, it is either a real right (jus reale), or a personal right (jus personale), or a real-personal right (jus realiter personale), to the possession although not to the use, of another person as if he were a thing.

III. In respect of the ground of right or the title (titulus) of acquisition—which, properly, is not a particular member of the division of rights, but rather a constituent element of the mode of exercising them—anything external is acquired by a certain free exercise of will that is either unilateral, as the act of a single will (facto), or bilateral, as the act of two wills (pacto), or omnilateral, as the act of all the wills of a community together (lege).