Ownership then is the right by which the substance, so to speak, of a thing belongs to ft man, so that it does not belong as a whole in the same way to another. Hence it follows that we can dispose as we please of things belonging properly to us, and can have acquired a special right from us by agreement. Yet in states it usually happens that ownership is not always unrestricted in the case of all men, but circumscribed with certain limits by civil authority, or by an arrangement or convention which men have made with each other. When one thing, however, belongs to several in the same way and without division, it is said to be common to those persons. For if things are useful indeed to men, but yet inexhaustible, so that they can be free for all to use, and still the individual's use is not thereby more niggardly, it would be superfluous and foolish to wish to divide them.
Examples are the sun's heat and light, air, running water, and the like.
For when a thing is so constituted that others cannot by any means be excluded from its use, to divide it, or make property of it, is superfluous, and also apt to furnish occasion for vain litigation. The methods of acquiring ownership are either original or derivative. After individual ownership of things had been adopted among men, it was agreed by them that whatever had not come under the primitive division should fall to the occupant, that is, the first man to seize the thing by physical means, with intent to keep it for himself. Hence to-day the only original method of acquiring ownership of the substance of a thing is occupancy. By this means then we acquire desert regions which no man ever claimed as his.