Objection 1. It would seem that the soul of man is not carried away to things divine. For some define rapture as "an uplifting by the power of a higher nature, from that which is according to nature to that which is above nature" [Reference unknown; Cf. De Veritate xiii, 1. Now it is in accordance with man's nature that he be uplifted to things divine; for Augustine says at the beginning of his Confessions: "Thou madest us, Lord, for Thyself, and our heart is restless, till it rest in Thee." Therefore man's soul is not carried away to things divine.
Objection 2. Further, Dionysius says (Div. Nom. viii) that "God's justice is seen in this that He treats all things according to their mode and dignity." But it is not in accordance with man's mode and worth that he be raised above what he is according to nature. Therefore it would seem that man's soul is not carried away to things divine.
Objection 3. Further, rapture denotes violence of some kind. But God rules us not by violence or force, as Damascene says [De Fide Orth. ii, 30]. Therefore man's soul is not carried away to things divine.
On the contrary, The Apostle says (2 Corinthians 12:2): "I know a man in Christ... rapt even to the third heaven." On which words a gloss says: "Rapt, that is to say, uplifted contrary to nature."
I answer that, Rapture denotes violence of a kind as stated above (Objection 3); and "the violent is that which has its principle without, and in which he that suffers violence concurs not at all" (Ethic. iii, 1). Now everything concurs in that to which it tends in accordance with its proper inclination, whether voluntary or natural. Wherefore he who is carried away by some external agent, must be carried to something different from that to which his inclination tends. This difference arises in two ways: in one way from the end of the inclination--for instance a stone, which is naturally inclined to be borne downwards, may be thrown upwards; in another way from the manner of tending--for instance a stone may be thrown downwards with greater velocity than consistent with its natural movement.
Accordingly man's soul also is said to be carried away, in a twofold manner, to that which is contrary to its nature: in one way, as regards the term of transport--as when it is carried away to punishment, according to Psalm 49:22, "Lest He snatch you away, and there be none to deliver you"; in another way, as regards the manner connatural to man, which is that he should understand the truth through sensible things. Hence when he is withdrawn from the apprehension of sensibles, he is said to be carried away, even though he be uplifted to things whereunto he is directed naturally: provided this be not done intentionally, as when a man betakes himself to sleep which is in accordance with nature, wherefore sleep cannot be called rapture, properly speaking.
This withdrawal, whatever its term may be, may arise from a threefold cause. First, from a bodily cause, as happens to those who suffer abstraction from the senses through weakness: secondly, by the power of the demons, as in those who are possessed: thirdly, by the power of God. In this last sense we are now speaking of rapture, whereby a man is uplifted by the spirit of God to things supernatural, and withdrawn from his senses, according to Ezekiel 8:3, "The spirit lifted me up between the earth and the heaven, and brought me in the vision of God into Jerusalem."
It must be observed, however, that sometimes a person is said to be carried away, not only through being withdrawn from his senses, but also through being withdrawn from the things to which he was attending, as when a person's mind wanders contrary to his purpose. But this is to use the expression in a less proper signification.
Reply to Objection 1. It is natural to man to tend to divine things through the apprehension of things sensible, according to Romans 1:20, "The invisible things of God... are clearly seen, being understood by the things that are made." But the mode, whereby a man is uplifted to divine things and withdrawn from his senses, is not natural to man.
Reply to Objection 2. It belongs to man's mode and dignity that he be uplifted to divine things, from the very fact that he is made to God's image. And since a divine good infinitely surpasses the faculty of man in order to attain that good, he needs the divine assistance which is bestowed on him in every gift of grace. Hence it is not contrary to nature, but above the faculty of nature that man's mind be thus uplifted in rapture by God.
Reply to Objection 3. The saying of Damascene refers to those things which a man does by himself. But as to those things which are beyond the scope of the free-will, man needs to be uplifted by a stronger operation, which in a certain respect may be called force if we consider the mode of operation, but not if we consider its term to which man is directed both by nature and by his intention.
Source: Summa Theologica (New Advent)