Obj. 2:  Further, 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 contrary, Augustine says (QQ. 83, qu. 30):  “None but a rational animal can make use of a thing.”

I answer that, as 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 Obj. 1:  To 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 Obj. 2:  Animals 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. ________________________

THIRD ARTICLE [I-II, Q. 16, Art. 3]

Whether Use Regards Also the Last End?

Objection 1:  It 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.

Obj. 2:  Further, “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.

Obj. 3:  Further, 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 contrary, Augustine 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 that, Use, 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.