Objection 1. It would seem that rapture pertains to the appetitive rather than to the cognitive power. For Dionysius says (Div. Nom. iv): "The Divine love causes ecstasy." Now love pertains to the appetitive power. Therefore so does ecstasy or rapture.
Objection 2. Further, Gregory says (Dial. ii, 3) that "he who fed the swine debased himself by a dissipated mind and an unclean life; whereas Peter, when the angel delivered him and carried him into ecstasy, was not beside himself, but above himself." Now the prodigal son sank into the depths by his appetite. Therefore in those also who are carried up into the heights it is the appetite that is affected.
Objection 3. Further, a gloss on Psalm 30:1, "In Thee, O Lord, have I hoped, let me never be confounded," says in explaining the title [Unto the end, a psalm for David, in an ecstasy]: "Ekstasis in Greek signifies in Latin 'excessus mentis,' an aberration of the mind. This happens in two ways, either through dread of earthly things or through the mind being rapt in heavenly things and forgetful of this lower world." Now dread of earthly things pertains to the appetite. Therefore rapture of the mind in heavenly things, being placed in opposition to this dread, also pertains to the appetite.
On the contrary, A gloss on Psalm 115:2, "I said in my excess: Every man is a liar," says: "We speak of ecstasy, not when the mind wanders through fear, but when it is carried aloft on the wings of revelation." Now revelation pertains to the intellective power. Therefore ecstasy or rapture does also.
I answer that, We can speak of rapture in two ways. First, with regard to the term of rapture, and thus, properly speaking, rapture cannot pertain to the appetitive, but only to the cognitive power. For it was stated (1) that rapture is outside the inclination of the person who is rapt; whereas the movement of the appetitive power is an inclination to an appetible good. Wherefore, properly speaking, in desiring something, a man is not rapt, but is moved by himself.
Secondly, rapture may be considered with regard to its cause, and thus it may have a cause on the part of the appetitive power. For from the very fact that the appetite is strongly affected towards something, it may happen, owing to the violence of his affection, that a man is carried away from everything else. Moreover, it has an effect on the appetitive power, when for instance a man delights in the things to which he is rapt. Hence the Apostle said that he was rapt, not only "to the third heaven"--which pertains to the contemplation of the intellect--but also into "paradise," which pertains to the appetite.
Reply to Objection 1. Rapture adds something to ecstasy. For ecstasy means simply a going out of oneself by being placed outside one's proper order [Cf. I-II, 28, 3]; while rapture denotes a certain violence in addition. Accordingly ecstasy may pertain to the appetitive power, as when a man's appetite tends to something outside him, and in this sense Dionysius says that "the Divine love causes ecstasy," inasmuch as it makes man's appetite tend to the object loved. Hence he says afterwards that "even God Himself, the cause of all things, through the overflow of His loving goodness, goes outside Himself in His providence for all beings." But even if this were said expressly of rapture, it would merely signify that love is the cause of rapture.
Reply to Objection 2. There is a twofold appetite in man; to wit, the intellective appetite which is called the will, and the sensitive appetite known as the sensuality. Now it is proper to man that his lower appetite be subject to the higher appetite, and that the higher move the lower. Hence man may become outside himself as regards the appetite, in two ways. On one way, when a man's intellective appetite tends wholly to divine things, and takes no account of those things whereto the sensitive appetite inclines him; thus Dionysius says (Div. Nom. iv) that "Paul being in ecstasy through the vehemence of Divine love" exclaimed: "I live, now not I, but Christ liveth in me."
In another way, when a man tends wholly to things pertaining to the lower appetite, and takes no account of his higher appetite. It is thus that "he who fed the swine debased himself"; and this latter kind of going out of oneself, or being beside oneself, is more akin than the former to the nature of rapture because the higher appetite is more proper to man. Hence when through the violence of his lower appetite a man is withdrawn from the movement of his higher appetite, it is more a case of being withdrawn from that which is proper to him. Yet, because there is no violence therein, since the will is able to resist the passion, it falls short of the true nature of rapture, unless perchance the passion be so strong that it takes away entirely the use of reason, as happens to those who are mad with anger or love.
It must be observed. however, that both these excesses affecting the appetite may cause an excess in the cognitive power, either because the mind is carried away to certain intelligible objects, through being drawn away from objects of sense, or because it is caught up into some imaginary vision or fanciful apparition.
Reply to Objection 3. Just as love is a movement of the appetite with regard to good, so fear is a movement of the appetite with regard to evil. Wherefore either of them may equally cause an aberration of mind; and all the more since fear arises from love, as Augustine says (De Civ. Dei xiv, 7,9).
Source: Summa Theologica (New Advent)