Iul. Pacii Iuriscons. in L. frater à fratre D. de condictione indebiti, commentarius

Why is a peculiar natural obligation (such as the obligation about which we are dealing in our law) not acquired for the father rather than the son, if indeed the peculium is the father's and not the son's (Digest 4.4.3, § "sed utrum")? Finally, the son acquires for the father because he is in his power. For by the same reason, a slave also acquires for the master (Digest 1.6.1). And an emancipated son no longer acquires. Since, therefore, the paternal power original: "patria potestas" is not only civil (Digest 1.6.3-4; Institutes 1.8, § "ius autem"), but also of the law of nations (Digest 1.1.2; Code 6.59, last law in the end; Institutes 1.10, in the opening; Politics 1.1), inasmuch as it is observed among all nations: it follows that not only is a civil obligation, but also an obligation of the law of nations (which is called natural) acquired for the father. But here someone will object: "All men are by nature equal" (Digest 50.17.33). The response is ready. That law speaks of natural law common to all animals. We speak of the law of nations. It is certain that men are not distinguished by that natural law, but by the law of nations (Digest 1.1.4); and that we look to the law of nations when we speak of a natural obligation has been shown above.