There is, however, no such thing as private ownership established by nature, but property becomes private either through long occupancy (as in the case of those who long ago settled in unoccupied territory) or through conquest (as in the case of those who took it in war) or by due process of law, bargain, or purchase, or by allotment. On this principle the lands of Arpinum are said to belong to the Arpinates, the Tusculan lands to the Tusculans; and similar is the assignment of private property. Therefore, inasmuch as in each case some of those things which by nature had been common property became the property of individuals, each one should retain possession of that which has fallen to his lot; and if anyone appropriates to himself anything beyond that, he will be violating the laws of human society.
The quote: But since, as Plato has admirably expressed it, we are not born for ourselves alone, but our country claims a share of our being, and our friends a share;
and since, as the Stoics hold, everything that the earth produces is created for man's use; and as men, too, are born for the sake of men, that they may be able mutually to help one another; in this direction we ought to follow Nature as our guide, to contribute to the general good by an interchange of acts of kindness, by giving and receiving, and thus by our skill, our industry, and our talents to cement human society more closely together, man to man. The foundation of justice, moreover, is good faith— that is, truth and fidelity to promises and agreements.