Objection 1. It would seem that to enjoy belongs not only to the appetitive power. For to enjoy seems nothing else than to receive the fruit. But it is the intellect, in whose act Happiness consists, as shown above (Question 3, Article 04), that receives the fruit of human life, which is Happiness. Therefore to enjoy is not an act of the appetitive power, but of the intellect.
Objection 2. Further, each power has its proper end, which is its perfection: thus the end of sight is to know the visible; of the hearing, to perceive sounds; and so forth. But the end of a thing is its fruit. Therefore to enjoy belongs to each power, and not only to the appetite.
Objection 3. Further, enjoyment implies a certain delight. But sensible delight belongs to sense, which delights in its object: and for the same reason, intellectual delight belongs to the intellect. Therefore enjoyment belongs to the apprehensive, and not to the appetitive power.
On the contrary, Augustine says (De Doctr. Christ. i, 4; and De Trin. x, 10,11): "To enjoy is to adhere lovingly to something for its own sake." But love belongs to the appetitive power. Therefore also to enjoy is an act of the appetitive power.
I answer that, "Fruitio" [enjoyment] and "fructus" [fruit] seem to refer to the same, one being derived from the other; which from which, matters not for our purpose; though it seems probable that the one which is more clearly known, was first named. Now those things are most manifest to us which appeal most to the senses: wherefore it seems that the word "fruition" is derived from sensible fruits. But sensible fruit is that which we expect the tree to produce in the last place, and in which a certain sweetness is to be perceived. Hence fruition seems to have relation to love, or to the delight which one has in realizing the longed-for term, which is the end. Now the end and the good is the object of the appetitive power. Wherefore it is evident that fruition is the act of the appetitive power.
Reply to Objection 1. Nothing hinders one and the same thing from belonging, under different aspects, to different powers. Accordingly the vision of God, as vision, is an act of the intellect, but as a good and an end, is the object of the will. And as such is the fruition thereof: so that the intellect attains this end, as the executive power, but the will as the motive power, moving (the powers) towards the end and enjoying the end attained.
Reply to Objection 2. The perfection and end of every other power is contained in the object of the appetitive power, as the proper is contained in the common, as stated above (Question 9, Article 1). Hence the perfection and end of each power, in so far as it is a good, belongs to the appetitive power. Wherefore the appetitive power moves the other powers to their ends; and itself realizes the end, when each of them reaches the end.
Reply to Objection 3. In delight there are two things: perception of what is becoming; and this belongs to the apprehensive power; and complacency in that which is offered as becoming: and this belongs to the appetitive power, in which power delight is formally completed.
Source: Summa Theologica (New Advent)