Objection 1. It would seem that the beatitudes do not differ from the virtues and gifts. For Augustine (De Serm. Dom. in Monte i, 4) assigns the beatitudes recited by Matthew (v 3, seqq.) to the gifts of the Holy Ghost; and Ambrose in his commentary on Luke 6:20, seqq., ascribes the beatitudes mentioned there, to the four cardinal virtues. Therefore the beatitudes do not differ from the virtues and gifts.
Objection 2. Further, there are but two rules of the human will: the reason and the eternal law, as stated above (19, 3; 21, 1). Now the virtues perfect man in relation to reason; while the gifts perfect him in relation to the eternal law of the Holy Ghost, as is clear from what has been said (68, A1,3, seqq.). Therefore there cannot be anything else pertaining to the rectitude of the human will, besides the virtues and gifts. Therefore the beatitudes do not differ from them.
Objection 3. Further, among the beatitudes are included meekness, justice, and mercy, which are said to be virtues. Therefore the beatitudes do not differ from the virtues and gifts.
On the contrary, Certain things are included among the beatitudes, that are neither virtues nor gifts, e.g. poverty, mourning, and peace. Therefore the beatitudes differ from the virtues and gifts.
I answer that, As stated above (2, 7; 3, 1), happiness is the last end of human life. Now one is said to possess the end already, when one hopes to possess it; wherefore the Philosopher says (Ethic. i, 9) that "children are said to be happy because they are full of hope"; and the Apostle says (Romans 8:24): "We are saved by hope." Again, we hope to obtain an end, because we are suitably moved towards that end, and approach thereto; and this implies some action. And a man is moved towards, and approaches the happy end by works of virtue, and above all by the works of the gifts, if we speak of eternal happiness, for which our reason is not sufficient, since we need to be moved by the Holy Ghost, and to be perfected with His gifts that we may obey and follow him. Consequently the beatitudes differ from the virtues and gifts, not as habit, but as act from habit.
Reply to Objection 1. Augustine and Ambrose assign the beatitudes to the gifts and virtues, as acts are ascribed to habits. But the gifts are more excellent than the cardinal virtues, as stated above (Question 68, Article 8). Wherefore Ambrose, in explaining the beatitudes propounded to the throng, assigns them to the cardinal virtues, whereas Augustine, who is explaining the beatitudes delivered to the disciples on the mountain, and so to those who were more perfect, ascribes them to the gifts of the Holy Ghost.
Reply to Objection 2. This argument proves that no other habits, besides the virtues and gifts, rectify human conduct.
Reply to Objection 3. Meekness is to be taken as denoting the act of meekness: and the same applies to justice and mercy. And though these might seem to be virtues, they are nevertheless ascribed to gifts, because the gifts perfect man in all matters wherein the virtues perfect him, as stated above (Question 68, Article 2).
Source: Summa Theologica (New Advent)