Summa summae S. Thomae, Tomus III

Since right taken in the second way, for the faculty of doing something, acquiring, etc., is the foundation of right or of the just, which is the object of justice, many necessary points concerning it occur to be examined, especially concerning dominion, which is its principal species.

Dominion is twofold: one of jurisdiction, which is the power of governing one's subjects; the other of property, which is the faculty of disposing of some thing as one's own for one's own advantage, and it is chiefly of this that we treat here.

Dominion of property again is twofold: one full and perfect, the other not full and imperfect.

Full dominion is the right to the property of a thing and its emoluments. Not full is the right to the property of a thing without the emoluments, and it is called direct dominion, such, e. g., as belongs to the prince with respect to a fief; or the right to the emoluments without the property, and it is called useful dominion, and such belongs to usufructuaries, feudatories, emphyteutae, etc.

Therefore

I say first: Full and perfect dominion of property, as it embraces direct and useful dominion, is rightly defined: "A right in a thing, or the legitimate faculty of disposing of a thing as one's own, for any use not prohibited by law, for one's own advantage." It is gathered from D. Thomas, here q. 66, a. 1, c.

It is said, "for any use not prohibited by law;" because, although dominion by its nature bestows power for any use whatever, this power can nevertheless be impeded by law so that it does not pass into act: as happens with a minor, who before the legitimate age cannot alienate his goods, although he is their true owner; hence, if he were to alienate them, he would not sin against justice.

But the same conditions are required for perfect dominion that are required for right in a thing, namely: the existence of the thing, a legitimate title, and delivery of the thing.

I say secondly: Usufruct is defined: "The right of using and enjoying the things of another, saving their substance." So in the law.

It is said, "of enjoying," that it may be distinguished from simple use.

For he who has simple use can only use the thing, e. g., a horse, a house, a garden, a field, a wood, etc., for his own daily necessity, so that he can neither let, sell, nor gratuitously cede to another either the superfluous fruits or the right he has; whereas he who has usufruct can do all these things, so L. 12, ff. de Usu.

But fruits are reckoned not only in immovables, as hay, crops, shoots, timber trees, bois taillis in an estate (for fruit-bearing trees are not reckoned fruits), but also in movables, as wool, milk, offspring, etc., in a flock. Where note that timber wood, even if cut out of season, is in fruit, just as an olive picked unripe, likewise hay cut unripe. L. 48, ff. de Usufructu. As to harvest and vintage, however, the usufructuary must wait for ripeness.

Note further that, if the usufructuary die before he has gathered the fruits, even if ripe, these are acquired by the owner of the property, and not by the heirs of the usufructuary. So in Instit. de Rerum divisione, § Is vero. The reason is, because as long as they adhere to the estate they are held to be one with it. Hence they belong to the owner of the estate until the usufructuary by gathering them has made them his own.

It is said, "the things of another;" because usufruct is a servitude, which can be constituted only over the things of another. "For no one's own thing serves him, but profits him by right of dominion," as is said in L. 26, ff. de servitute praedior. rustic.

It is said, "saving their substance;" because the usufructuary must reserve the thing intact for the proprietor. Hence usufruct cannot properly be constituted over things that are consumed by a single use, as wine, oil, etc.

I say thirdly: Use is defined by the jurists: "The right of only using the things of another, saving their substance."

It is said the right of only using, and not of enjoying; because, as I have already said, the simple user can only take the fruits of a thing, as vegetables, apples, hay, for his own daily necessity, but he cannot sell or give them away, nor let the thing itself; which the usufructuary can do.

It is said, "saving their substance," because in use, as in usufruct, the thing must be preserved intact for the owner.

From this you have that this definition of use does not belong to things consumable by a single act, as wine, oil, bread, etc.; because by such use the substance of the thing does not remain safe. Hence, if use be taken more generally, as it befits both things consumable by a single act and non-consumable things, it is "the right of using a thing of another."

Concerning this use of things consumable by a single act there was once great controversy, not only among theologians, but also among Pontiffs: whether it should be distinguished from dominion? For whose resolution let there be