Objection 1. It seems that the seventh beatitude does not correspond to the gift of wisdom. For the seventh beatitude is: "Blessed are the peacemakers, for they shall be called the children of God." Now both these things belong to charity: since of peace it is written (Psalm 118:165): "Much peace have they that love Thy law," and, as the Apostle says (Romans 5:5), "the charity of God is poured forth in our hearts by the Holy Ghost Who is given to us," and Who is "the Spirit of adoption of sons, whereby we cry: Abba [Father]" (Romans 8:15). Therefore the seventh beatitude ought to be ascribed to charity rather than to wisdom.
Objection 2. Further, a thing is declared by its proximate effect rather than by its remote effect. Now the proximate effect of wisdom seems to be charity, according to Wisdom 7:27: "Through nations she conveyeth herself into holy souls; she maketh the friends of God and prophets": whereas peace and the adoption of sons seem to be remote effects, since they result from charity, as stated above (Question 29, Article 3). Therefore the beatitude corresponding to wisdom should be determined in respect of the love of charity rather than in respect of peace.
Objection 3. Further, it is written (James 3:17): "The wisdom, that is from above, first indeed is chaste, then peaceable, modest, easy to be persuaded, consenting to the good, full of mercy and good fruits, judging without dissimulation [Vulgate: 'without judging, without dissimulation']." Therefore the beatitude corresponding to wisdom should not refer to peace rather than to the other effects of heavenly wisdom.
On the contrary, Augustine says (De Serm. Dom. in Monte i, 4) that "wisdom is becoming to peacemakers, in whom there is no movement of rebellion, but only obedience to reason."
I answer that, The seventh beatitude is fittingly ascribed to the gift of wisdom, both as to the merit and as to the reward. The merit is denoted in the words, "Blessed are the peacemakers." Now a peacemaker is one who makes peace, either in himself, or in others: and in both cases this is the result of setting in due order those things in which peace is established, for "peace is the tranquillity of order," according to Augustine (De Civ. Dei xix, 13). Now it belongs to wisdom to set things in order, as the Philosopher declares (Metaph. i, 2), wherefore peaceableness is fittingly ascribed to wisdom. The reward is expressed in the words, "they shall be called the children of God." Now men are called the children of God in so far as they participate in the likeness of the only-begotten and natural Son of God, according to Romans 8:29, "Whom He foreknew... to be made conformable to the image of His Son," Who is Wisdom Begotten. Hence by participating in the gift of wisdom, man attains to the sonship of God.
Reply to Objection 1. It belongs to charity to be at peace, but it belongs to wisdom to make peace by setting things in order. Likewise the Holy Ghost is called the "Spirit of adoption" in so far as we receive from Him the likeness of the natural Son, Who is the Begotten Wisdom.
Reply to Objection 2. These words refer to the Uncreated Wisdom, which in the first place unites itself to us by the gift of charity, and consequently reveals to us the mysteries the knowledge of which is infused wisdom. Hence, the infused wisdom which is a gift, is not the cause but the effect of charity.
Reply to Objection 3. As stated above (Article 3) it belongs to wisdom, as a gift, not only to contemplate Divine things, but also to regulate human acts. Now the first thing, to be effected in this direction of human acts is the removal of evils opposed to wisdom: wherefore fear is said to be "the beginning of wisdom," because it makes us shun evil, while the last thing is like an end, whereby all things are reduced to their right order; and it is this that constitutes peace. Hence James said with reason that "the wisdom that is from above" (and this is the gift of the Holy Ghost) "first indeed is chaste," because it avoids the corruption of sin, and "then peaceable," wherein lies the ultimate effect of wisdom, for which reason peace is numbered among the beatitudes. As to the things that follow, they declare in becoming order the means whereby wisdom leads to peace. For when a man, by chastity, avoids the corruption of sin, the first thing he has to do is, as far as he can, to be moderate in all things, and in this respect wisdom is said to be modest. Secondly, in those matters in which he is not sufficient by himself, he should be guided by the advice of others, and as to this we are told further that wisdom is "easy to be persuaded." These two are conditions required that man may be at peace with himself. But in order that man may be at peace with others it is furthermore required, first that he should not be opposed to their good; this is what is meant by "consenting to the good." Secondly, that he should bring to his neighbor's deficiencies, sympathy in his heart, and succor in his actions, and this is denoted by the words "full of mercy and good fruits." Thirdly, he should strive in all charity to correct the sins of others, and this is indicated by the words "judging without dissimulation [Vulgate: 'The wisdom that is from above... is... without judging, without dissimulation']," lest he should purpose to sate his hatred under cover of correction.
Source: Summa Theologica (New Advent)