Summa Theologica I-II, q. 16: Of Use, which is an Act of the Will in Regard to the Means
Article 2. Whether use is to be found in irrational animals?
Objection 1It would seem that use is to be found in irrational animals. For it is better to enjoy than to use, because, as Augustine says (De Trin. x, 10): "We use things by referring them to something else which we are to enjoy." But enjoyment is to be found in irrational animals, as stated above (Q[11], A[2]). Much more, therefore, is it possible for them to use.
Objection 2Further, to apply the members to action is to use them. But irrational animals apply their members to action; for instance, their feet, to walk; their horns, to strike. Therefore it is possible for irrational animals to use.
On the contraryAugustine says (QQ. 83, qu. 30): "None but a rational animal can make use of a thing."
I answer thatas stated above (A[1]), to use is to apply an active principle to action: thus to consent is to apply the appetitive movement to the desire of something, as stated above (Q[15], AA[1],2,3). Now he alone who has the disposal of a thing, can apply it to something else; and this belongs to him alone who knows how to refer it to something else, which is an act of the reason. And therefore none but a rational animal consents and uses.
Reply to Objection 1To enjoy implies the absolute movement of the appetite to the appetible: whereas to use implies a movement of the appetite to something as directed to something else. If therefore we compare use and enjoyment in respect of their objects, enjoyment is better than use; because that which is appetible absolutely is better than that which is appetible only as directed to something else. But if we compare them in respect of the apprehensive power that precedes them, greater excellence is required on the part of use: because to direct one thing to another is an act of reason; whereas to apprehend something absolutely is within the competency even of sense.
Reply to Objection 2Animals by means of their members do something from natural instinct; not through knowing the relation of their members to these operations. Wherefore, properly speaking, they do not apply their members to action, nor do they use them.
Article 3. Whether use regards also the last end?
Objection 1It would seem that use can regard also the last end. For Augustine says (De Trin. x, 11): "Whoever enjoys, uses." But man enjoys the last end. Therefore he uses the last end.
Objection 2Further, "to use is to apply something to the purpose of the will" (De Trin. x, 11). But the last end, more than anything else, is the object of the will's application. Therefore it can be the object of use.
Objection 3Further, Hilary says (De Trin. ii) that "Eternity is in the Father, Likeness in the Image," i.e. in the Son, "Use in the Gift," i.e. in the Holy Ghost. But the Holy Ghost, since He is God, is the last end. Therefore the last end can be the object of use.
On the contraryAugustine says (QQ. 83, qu. 30): "No one rightly uses God, but one enjoys Him." But God alone is the last end. Therefore we cannot use the last end.
I answer thatUse, as stated above (A[1]), implies the application of one thing to another. Now that which is applied to another is regarded in the light of means to an end; and consequently use always regards the means. For this reason things that are adapted to a certain end are said to be "useful"; in fact their very usefulness is sometimes called use.
It must, however, be observed that the last end may be taken in two ways: first, simply; secondly, in respect of an individual. For since the end, as stated above (Q[1], A[8]; Q[2], A[7]), signifies sometimes the thing itself, and sometimes the attainment or possession of that thing (thus the miser's end is either money or the possession of it); it is evident that, simply speaking, the last end is the thing itself; for the possession of money is good only inasmuch as there is some good in money. But in regard to the individual, the obtaining of money is the last end; for the miser would not seek for money, save that he might have it. Therefore, simply and properly speaking, a man enjoys money, because he places his last end therein; but in so far as he seeks to possess it, he is said to use it.
Reply to Objection 1Augustine is speaking of use in general, in so far as it implies the relation of an end to the enjoyment which a man seeks in that end.
Reply to Objection 2The end is applied to the purpose of the will, that the will may find rest in it. Consequently this rest in the end, which is the enjoyment thereof, is in this sense called use of the end. But the means are applied to the will's purpose, not only in being used as means, but as ordained to something else in which the will finds rest.
Reply to Objection 3The words of Hilary refer to use as applicable to rest in the last end; just as, speaking in a general sense, one may be said to use the end for the purpose of attaining it, as stated above. Hence Augustine says (De Trin. vi, 10) that "this love, delight, felicity, or happiness, is called use by him."