Objection 1. It would seem that there are not any theological virtues. For according to Phys. vii, text. 17, "virtue is the disposition of a perfect thing to that which is best: and by perfect, I mean that which is disposed according to nature." But that which is Divine is above man's nature. Therefore the theological virtues are not virtues of a man.
Objection 2. Further, theological virtues are quasi-Divine virtues. But the Divine virtues are exemplars, as stated above (Question 61, Article 5), which are not in us but in God. Therefore the theological virtues are not virtues of man.
Objection 3. Further, the theological virtues are so called because they direct us to God, Who is the first beginning and last end of all things. But by the very nature of his reason and will, man is directed to his first beginning and last end. Therefore there is no need for any habits of theological virtue, to direct the reason and will to God.
On the contrary, The precepts of the Law are about acts of virtue. Now the Divine Law contains precepts about the acts of faith, hope, and charity: for it is written (Sirach 2:8, seqq.): "Ye that fear the Lord believe Him," and again, "hope in Him," and again, "love Him." Therefore faith, hope, and charity are virtues directing us to God. Therefore they are theological virtues.
I answer that, Man is perfected by virtue, for those actions whereby he is directed to happiness, as was explained above (Question 5, Article 7). Now man's happiness is twofold, as was also stated above (Question 5, Article 5). One is proportionate to human nature, a happiness, to wit, which man can obtain by means of his natural principles. The other is a happiness surpassing man's nature, and which man can obtain by the power of God alone, by a kind of participation of the Godhead, about which it is written (2 Peter 1:4) that by Christ we are made "partakers of the Divine nature." And because such happiness surpasses the capacity of human nature, man's natural principles which enable him to act well according to his capacity, do not suffice to direct man to this same happiness. Hence it is necessary for man to receive from God some additional principles, whereby he may be directed to supernatural happiness, even as he is directed to his connatural end, by means of his natural principles, albeit not without Divine assistance. Such like principles are called "theological virtues": first, because their object is God, inasmuch as they direct us aright to God: secondly, because they are infused in us by God alone: thirdly, because these virtues are not made known to us, save by Divine revelation, contained in Holy Writ.
Reply to Objection 1. A certain nature may be ascribed to a certain thing in two ways. First, essentially: and thus these theological virtues surpass the nature of man. Secondly, by participation, as kindled wood partakes of the nature of fire: and thus, after a fashion, man becomes a partaker of the Divine Nature, as stated above: so that these virtues are proportionate to man in respect of the Nature of which he is made a partaker.
Reply to Objection 2. These virtues are called Divine, not as though God were virtuous by reason of them, but because of them God makes us virtuous, and directs us to Himself. Hence they are not exemplar but exemplate virtues.
Reply to Objection 3. The reason and will are naturally directed to God, inasmuch as He is the beginning and end of nature, but in proportion to nature. But the reason and will, according to their nature, are not sufficiently directed to Him in so far as He is the object of supernatural happiness.
Source: Summa Theologica (New Advent)