Objection 1. It would seem that the beatitudes are unsuitably enumerated. For the beatitudes are assigned to the gifts, as stated above (1, ad 1). Now some of the gifts, viz. wisdom and understanding, belong to the contemplative life: yet no beatitude is assigned to the act of contemplation, for all are assigned to matters connected with the active life. Therefore the beatitudes are insufficiently enumerated.
Objection 2. Further, not only do the executive gifts belong to the active life, but also some of the directive gifts, e.g. knowledge and counsel: yet none of the beatitudes seems to be directly connected with the acts of knowledge or counsel. Therefore the beatitudes are insufficiently indicated.
Objection 3. Further, among the executive gifts connected with the active life, fear is said to be connected with poverty, while piety seems to correspond to the beatitude of mercy: yet nothing is included directly connected with justice. Therefore the beatitudes are insufficiently enumerated.
Objection 4. Further, many other beatitudes are mentioned in Holy Writ. Thus, it is written (Job 5:17): "Blessed is the man whom God correcteth"; and (Psalm 1:1): "Blessed is the man who hath not walked in the counsel of the ungodly"; and (Proverbs 3:13): "Blessed is the man that findeth wisdom." Therefore the beatitudes are insufficiently enumerated.
Objection 5. On the other hand, it seems that too many are mentioned. For there are seven gifts of the Holy Ghost: whereas eight beatitudes are indicated.
Objection 6. Further, only four beatitudes are indicated in Luke 6. Therefore the seven or eight mentioned in Matthew 5 are too many.
I answer that, These beatitudes are most suitably enumerated. To make this evident it must be observed that beatitude has been held to consist in one of three things: for some have ascribed it to a sensual life, some, to an active life, and some, to a contemplative life [See 3]. Now these three kinds of happiness stand in different relations to future beatitude, by hoping for which we are said to be happy. Because sensual happiness, being false and contrary to reason, is an obstacle to future beatitude; while happiness of the active life is a disposition of future beatitude; and contemplative happiness, if perfect, is the very essence of future beatitude, and, if imperfect, is a beginning thereof.
And so Our Lord, in the first place, indicated certain beatitudes as removing the obstacle of sensual happiness. For a life of pleasure consists of two things. First, in the affluence of external goods, whether riches or honors; from which man is withdrawn--by a virtue so that he uses them in moderation--and by a gift, in a more excellent way, so that he despises them altogether. Hence the first beatitude is: "Blessed are the poor in spirit," which may refer either to the contempt of riches, or to the contempt of honors, which results from humility. Secondly, the sensual life consists in following the bent of one's passions, whether irascible or concupiscible. From following the irascible passions man is withdrawn--by a virtue, so that they are kept within the bounds appointed by the ruling of reason--and by a gift, in a more excellent manner, so that man, according to God's will, is altogether undisturbed by them: hence the second beatitude is: "Blessed are the meek." From following the concupiscible passions, man is withdrawn--by a virtue, so that man uses these passions in moderation--and by gift, so that, if necessary, he casts them aside altogether; nay more, so that, if need be, he makes a deliberate choice of sorrow [Cf. 35, 3]; hence the third beatitude is: "Blessed are they that mourn."
Active life consists chiefly in man's relations with his neighbor, either by way of duty or by way of spontaneous gratuity. To the former we are disposed--by a virtue, so that we do not refuse to do our duty to our neighbor, which pertains to justice--and by a gift, so that we do the same much more heartily, by accomplishing works of justice with an ardent desire, even as a hungry and thirsty man eats and drinks with eager appetite. Hence the fourth beatitude is: "Blessed are they that hunger and thirst after justice." With regard to spontaneous favors we are perfected--by a virtue, so that we give where reason dictates we should give, e.g. to our friends or others united to us; which pertains to the virtue of liberality--and by a gift, so that, through reverence for God, we consider only the needs of those on whom we bestow our gratuitous bounty: hence it is written (Luke 14:12-13): "When thou makest a dinner or supper, call not thy friends, nor thy brethren," etc... "but... call the poor, the maimed," etc.; which, properly, is to have mercy: hence the fifth beatitude is: "Blessed are the merciful."
Those things which concern the contemplative life, are either final beatitude itself, or some beginning thereof: wherefore they are included in the beatitudes, not as merits, but as rewards. Yet the effects of the active life, which dispose man for the contemplative life, are included in the beatitudes. Now the effect of the active life, as regards those virtues and gifts whereby man is perfected in himself, is the cleansing of man's heart, so that it is not defiled by the passions: hence the sixth beatitude is: "Blessed are the clean of heart." But as regards the virtues and gifts whereby man is perfected in relation to his neighbor, the effect of the active life is peace, according to Isaiah 32:17: "The work of justice shall be peace": hence the seventh beatitude is "Blessed are the peacemakers."
Reply to Objection 1. The acts of the gifts which belong to the active life are indicated in the merits: but the acts of the gifts pertaining to the contemplative life are indicated in the rewards, for the reason given above. Because to "see God" corresponds to the gift of understanding; and to be like God by being adoptive "children of God," corresponds to the gift of wisdom.
Reply to Objection 2. In things pertaining to the active life, knowledge is not sought for its own sake, but for the sake of operation, as even the Philosopher states (Ethic. ii, 2). And therefore, since beatitude implies something ultimate, the beatitudes do not include the acts of those gifts which direct man in the active life, such acts, to wit, as are elicited by those gifts, as, e.g. to counsel is the act of counsel, and to judge, the act of knowledge: but, on the other hand, they include those operative acts of which the gifts have the direction, as, e.g. mourning in respect of knowledge, and mercy in respect of counsel.
Reply to Objection 3. In applying the beatitudes to the gifts we may consider two things. One is likeness of matter. In this way all the first five beatitudes may be assigned to knowledge and counsel as to their directing principles: whereas they must be distributed among the executive gifts: so that, to wit, hunger and thirst for justice, and mercy too, correspond to piety, which perfects man in his relations to others; meekness to fortitude, for Ambrose says on Luke 6:22: "It is the business of fortitude to conquer anger, and to curb indignation," fortitude being about the irascible passions: poverty and mourning to the gift of fear, whereby man withdraws from the lusts and pleasures of the world.
Secondly, we may consider the motives of the beatitudes: and, in this way, some of them will have to be assigned differently. Because the principal motive for meekness is reverence for God, which belongs to piety. The chief motive for mourning is knowledge, whereby man knows his failings and those of worldly things, according to Ecclesiastes 1:18: "He that addeth knowledge, addeth also sorrow [Vulgate: labor]." The principal motive for hungering after the works of justice is fortitude of the soul: and the chief motive for being merciful is God's counsel, according to Daniel 4:24: "Let my counsel be acceptable to the king [Vulgate: to thee, O king]: and redeem thou thy sins with alms, and thy iniquities with works of mercy to the poor." It is thus that Augustine assigns them (De Serm. Dom. in Monte i, 4).
Reply to Objection 4. All the beatitudes mentioned in Holy Writ must be reduced to these, either as to the merits or as to the rewards: because they must all belong either to the active or to the contemplative life. Accordingly, when we read, "Blessed is the man whom the Lord correcteth," we must refer this to the beatitude of mourning: when we read, "Blessed is the man that hath not walked in the counsel of the ungodly," we must refer it to cleanness of heart: and when we read, "Blessed is the man that findeth wisdom," this must be referred to the reward of the seventh beatitude. The same applies to all others that can be adduced.
Reply to Objection 5. The eighth beatitude is a confirmation and declaration of all those that precede. Because from the very fact that a man is confirmed in poverty of spirit, meekness, and the rest, it follows that no persecution will induce him to renounce them. Hence the eighth beatitude corresponds, in a way, to all the preceding seven.
Reply to Objection 6. Luke relates Our Lord's sermon as addressed to the multitude (Luke 6:17). Hence he sets down the beatitudes according to the capacity of the multitude, who know no other happiness than pleasure, temporal and earthly: wherefore by these four beatitudes Our Lord excludes four things which seem to belong to such happiness. The first of these is abundance of external goods, which he sets aside by saying: "Blessed are ye poor." The second is that man be well off as to his body, in food and drink, and so forth; this he excludes by saying in the second place: "Blessed are ye that hunger." The third is that it should be well with man as to joyfulness of heart, and this he puts aside by saying: "Blessed are ye that weep now." The fourth is the outward favor of man; and this he excludes, saying, fourthly: "Blessed shall you be, when men shall hate you." And as Ambrose says on Luke 6:20, "poverty corresponds to temperance, which is unmoved by delights; hunger, to justice, since who hungers is compassionate and, through compassion gives; mourning, to prudence, which deplores perishable things; endurance of men's hatred belongs to fortitude."
Source: Summa Theologica (New Advent)