Summa Th. II-II EN Qu.89 a.8

Whether an oath is more binding than a vow?

Objection: 1. It would seem that an oath is more binding than a vow. A vow is a simple promise: whereas an oath includes, besides a promise, an appeal to God as witness. Therefore an oath is more binding than a vow.
2. Further, the weaker is wont to be confirmed by the stronger. Now a vow is sometimes confirmed by an oath. Therefore an oath is stronger than a vow.
3. Further, the obligation of a vow arises from the deliberation of the mind, a stated above (Question [88], Article [1]); while the obligation of an oath results from the truth of God Whose testimony is invoked. Since therefore God's truth is something greater than human deliberation, it seems that the obligation of an oath is greater than that of a vow.

On the contrary A vow binds one to God while an oath sometimes binds one to man. Now one is more bound to God than to man. Therefore a vow is more binding than an oath.
I answer that The obligation both of vow and of an oath arises from something Divine; but in different ways. For the obligation of a vow arises from the fidelity we owe God, which binds us to fulfil our promises to Him. On the other hand, the obligation of an oath arises from the reverence we owe Him which binds us to make true what we promise in His name. Now every act of infidelity includes an irreverence, but not conversely, because the infidelity of a subject to his lord would seem to be the greatest irreverence. Hence a vow by its very nature is more binding than an oath.

Reply to Objection: 1. A vow is not any kind of promise, but a promise made to God; and to be unfaithful to God is most grievous.
2. An oath is added to a vow not because it is more stable, but because greater stability results from "two immutable things" [*He 6,18].
3. Deliberation of the mind gives a vow its stability, on the part of the person who takes the vow: but it has a greater cause of stability on the part of God, to Whom the vow is offered.

Whether anyone can dispense from an oath?

Objection: 1. It would seem that no one can dispense from an oath. Just as truth is required for a declaratory oath, which is about the past or the present, so too is it required for a promissory oath, which is about the future. Now no one can dispense a man from swearing to the truth about present or past things. Therefore neither can anyone dispense a man from making truth that which he has promised by oath to do in the future.
2. Further, a promissory oath is used for the benefit of the person to whom the promise is made. But, apparently, he cannot release the other from his oath, since it would be contrary to the reverence of God. Much less therefore can a dispensation from this oath be granted by anyone.
3. Further, any bishop can grant a dispensation from a vow, except certain vows reserved to the Pope alone, as stated above (Question [88], Article [12], ad 3). Therefore in like manner, if an oath admits of dispensation, any bishop can dispense from an oath. And yet seemingly this is to be against the law [*Caus. XV, qu. 6, can. Auctoritatem, seqq.: Cap. Si vero, de Jurejurando]. Therefore it would seem that an oath does not admit of dispensation.

On the contrary A vow is more binding than an oath, as stated above (Article [8]). But a vow admits of dispensation and therefore an oath does also.
I answer that As stated above (Question [88], Article [10]), the necessity of a dispensation both from the law and from a vow arises from the fact that something which is useful and morally good in itself and considered in general, may be morally evil and hurtful in respect of some particular emergency: and such a case comes under neither law nor vow. Now anything morally evil or hurtful is incompatible with the matter of an oath: for if it be morally evil it is opposed to justice, and if it be hurtful it is contrary to judgment. Therefore an oath likewise admits of dispensation.

Reply to Objection: 1. A dispensation from an oath does not imply a permission to do anything against the oath: for this is impossible, since the keeping of an oath comes under a Divine precept, which does not admit of dispensation: but it implies that what hitherto came under an oath no longer comes under it, as not being due matter for an oath, just as we have said with regard to vows (Question [88], Article [10], ad 2). Now the matter of a declaratory oath, which is about something past or present, has already acquired a certain necessity, and has become unchangeable, wherefore the dispensation will regard not the matter but the act itself of the oath: so that such a dispensation would be directly contrary to the Divine precept. On the other hand, the matter of a promissory oath is something future, which admits of change, so that, to wit, in certain emergencies, it may be unlawful or hurtful, and consequently undue matter for an oath. Therefore a promissory oath admits of dispensation, since such dispensation regards the matter of an oath, and is not contrary to the Divine precept about the keeping of oaths.
2. One man may promise something under oath to another in two ways. First, when he promises something for his benefit: for instance, if he promise to serve him, or to give him money: and from such a promise he can be released by the person to whom he made it: for he is understood to have already kept his promise to him when he acts towards him according to his will. Secondly, one man promises another something pertaining to God's honor or to the benefit of others: for instance, if a man promise another under oath that he will enter religion, or perform some act of kindness. In this case the person to whom the promise is made cannot release him that made the promise, because it was made principally not to him but to God: unless perchance it included some condition, for instance, "provided he give his consent" or some such like condition.
3. Sometimes that which is made the matter of a promissory oath is manifestly opposed to justice, either because it is a sin, as when a man swears to commit a murder, or because it is an obstacle to a greater good, as when a man swears not to enter a religion: and such an oath requires no dispensation. But in the former case a man is bound not to keep such an oath, while in the latter it is lawful for him to keep or not to keep the oath, as stated above (Article [7], ad 2). Sometimes what is promised on oath is doubtfully right or wrong, useful or harmful, either in itself or under the circumstance. In this case any bishop can dispense. Sometimes, however, that which is promised under oath is manifestly lawful and beneficial. An oath of this kind seemingly admits not of dispensation but of commutation, when there occurs something better to be done for the common good, in which case the matter would seem to belong chiefly to the power of the Pope, who has charge over the whole Church; and even of absolute relaxation, for this too belongs in general to the Pope in all matters regarding the administration of things ecclesiastical. Thus it is competent to any man to cancel an oath made by one of his subjects in matters that come under his authority: for instance, a father may annul his daughter's oath, and a husband his wife's (Nb 30,6, seqq.), as stated above with regard to vows (Question [88], Articles [8],9).

Whether an oath is voided by a condition of person or time?

Objection: 1. It would seem that an oath is not voided by a condition of person or time. An oath, according to the Apostle (He 6,16), is employed for the purpose of confirmation. Now it is competent to anyone to confirm his assertion, and at any time. Therefore it would seem that an oath is not voided by a condition of person or time.
2. Further, to swear by God is more than to swear by the Gospels: wherefore Chrysostom [*Hom. xliv in the Opus Imperfectum falsely ascribed to St. John Chrysostom] says: "If there is a reason for swearing, it seems a small thing to swear by God, but a great thing to swear by the Gospels. To those who think thus, it must be said: Nonsense! the Scriptures were made for God's sake, not God for the sake of the Scriptures." Now men of all conditions and at all times are wont to swear by God. Much more, therefore, is it lawful to swear by the Gospels.
3. Further, the same effect does not proceed from contrary causes, since contrary causes produce contrary effects. Now some are debarred from swearing on account of some personal defect; children, for instance, before the age of fourteen, and persons who have already committed perjury. Therefore it would seem that a person ought not to be debarred from swearing either on account of his dignity, as clerics, or on account of the solemnity of the time.
4. Further, in this world no living man is equal in dignity to an angel: for it is written (Mt 11,11) that "he that is the lesser in the kingdom of heaven is greater than he," namely than John the Baptist, while yet living. Now an angel is competent to swear, for it is written (Ap 10,6) that the angel "swore by Him that liveth for ever and ever." Therefore no man ought to be excused from swearing, on account of his dignity.

On the contrary It is stated (II, qu. v, can. Si quis presbyter): "Let a priest be examined 'by his sacred consecration,' instead of being put on his oath": and (22, qu. v, can. Nullus): "Let no one in ecclesiastical orders dare to swear on the Holy Gospels to a layman."
I answer that Two things are to be considered in an oath. One is on the part of God, whose testimony is invoked, and in this respect we should hold an oath in the greatest reverence. For this reason children before the age of puberty are debarred from taking oaths [*Caus. XXII, qu. 5, can. Parvuli], and are not called upon to swear, because they have not yet attained the perfect use of reason, so as to be able to take a oath with due reverence. Perjurers also are debarred from taking an oath, because it is presumed from their antecedents that they will not treat an oath with the reverence due to it. For this same reason, in order that oaths might be treated with due reverence the law says (22, qu. v, can. Honestum): "It is becoming that he who ventures to swear on holy things should do so fasting, with all propriety and fear of God."The other thing to be considered is on the part of the man, whose assertion is confirmed by oath. For a man's assertion needs no confirmation save because there is a doubt about it. Now it derogates from a person's dignity that one should doubt about the truth of what he says, wherefore "it becomes not persons of great dignity to swear." For this reason the law says (II, qu. v, can. Si quis presbyter) that "priests should not swear for trifling reasons." Nevertheless it is lawful for them to swear if there be need for it, or if great good may result therefrom. Especially is this the case in spiritual affairs, when moreover it is becoming that they should take oath on days of solemnity, since they ought then to devote themselves to spiritual matters. Nor should they on such occasions take oaths temporal matters, except perhaps in cases grave necessity.

Reply to Objection: 1. Some are unable to confirm their own assertions on account of their own defect: and some there are whose words should be so certain that they need no confirmation.
2. The greater the thing sworn by, the holier and the more binding is the oath, considered in itself, as Augustine states (Ad Public., Ep. xlvii): and accordingly is a graver matter to swear by God than the Gospels. Yet the contrary may be the case on account of the manner of swearing for instance, an oath by the Gospels might be taken with deliberation and solemnity, and an oath by God frivolously and without deliberation.
3. Nothing prevents the same thing from arising out of contrary causes, by way of superabundance and defect. It is in this way that some are debarred from swearing, through being of so great authority that it is unbecoming for them to swear; while others are of such little authority that their oaths have no standing.
4. The angel's oath is adduced not on account of any defect in the angel, as though one ought not to credit his mere word, but in order to show that the statement made issues from God's infallible disposition. Thus too God is sometimes spoken of by Scripture as swearing, in order to express the immutability of His word, as the Apostle declares (He 6,17).


We must now consider the taking of God's name by way of adjuration: under which head there are three points of inquiry:

(1) Whether it is lawful to adjure a man?

(2) Whether it is lawful to adjure the demons?

(3) Whether it is lawful to adjure irrational creatures?

Whether it is lawful to adjure a man?

Objection: 1. It would seem that it is not lawful to adjure a man. Origen says (Tract. xxxv super Matth.): "I deem that a man who wishes to live according to the Gospel should not adjure another man. For if, according to the Gospel mandate of Christ, it be unlawful to swear, it is evident that neither is it lawful to adjure: and consequently it is manifest that the high-priest unlawfully adjured Jesus by the living God."
2. Further, whoever adjures a man, compels him after a fashion. But it is unlawful to compel a man against his will. Therefore seemingly it is also unlawful to adjure a man.
3. Further, to adjure is to induce a person to swear. Now it belongs to man's superior to induce him to swear, for the superior imposes an oath on his subject. Therefore subjects cannot adjure their superiors.

On the contrary Even when we pray God we implore Him by certain holy things: and the Apostle too besought the faithful "by the mercy of God" (Rm 12,1): and this seems to be a kind of adjuration. Therefore it is lawful to adjure.
I answer that A man who utters a promissory oath, swearing by his reverence for the Divine name, which he invokes in confirmation of his promise, binds himself to do what he has undertaken, and so orders himself unchangeably to do a certain thing. Now just as a man can order himself to do a certain thing, so too can he order others, by beseeching his superiors, or by commanding his inferiors, as stated above (Question [83], Article [1]). Accordingly when either of these orderings is confirmed by something Divine it is an adjuration. Yet there is this difference between them, that man is master of his own actions but not of those of others; wherefore he can put himself under an obligation by invoking the Divine name, whereas he cannot put others under such an obligation unless they be his subjects, whom he can compel on the strength of the oath they have taken.Therefore, if a man by invoking the name of God, or any holy thing, intends by this adjuration to put one who is not his subject under an obligation to do a certain thing, in the same way as he would bind himself by oath, such an adjuration is unlawful, because he usurps over another a power which he has not. But superiors may bind their inferiors by this kind of adjuration, if there be need for it.If, however, he merely intend, through reverence of the Divine name or of some holy thing, to obtain something from the other man without putting him under any obligation, such an adjuration may be lawfully employed in respect of anyone.

Reply to Objection: 1. Origen is speaking of an adjuration whereby a man intends to put another under an obligation, in the same way as he would bind himself by oath: for thus did the high-priest presume to adjure our Lord Jesus Christ [*Mt 26,63].
2. This argument considers the adjuration which imposes an obligation.
3. To adjure is not to induce a man to swear, but to employ terms resembling an oath in order to provoke another to do a certain thing.Moreover, we adjure God in one way and man in another; because when we adjure a man we intend to alter his will by appealing to his reverence for a holy thing: and we cannot have such an intention in respect of God Whose will is immutable. If we obtain something from God through His eternal will, it is due, not to our merits, but to His goodness.

Whether it is lawful to adjure the demons?

Objection: 1. It would seem unlawful to adjure the demons. Origen says (Tract. xxxv, super Matth.): "To adjure the demons is not accordance with the power given by our Saviour: for this is a Jewish practice." Now rather than imitate the rites of the Jews, we should use the power given by Christ. Therefore it is not lawful to adjure the demons.
2. Further, many make use of necromantic incantations when invoking the demons by something Divine: and this is an adjuration. Therefore, if it be lawful to adjure the demons, it is lawful to make use of necromantic incantations, which is evidently false. Therefore the antecedent is false also.
3. Further, whoever adjures a person, by that very fact associates himself with him. Now it is not lawful to have fellowship with the demons, according to 1Co 10,20, "I would not that you should be made partakers with devils." Therefore it is not lawful to adjure the demons.

On the contrary It is written (Mc 16,17): "In My name they shall cast out devils." Now to induce anyone to do a certain thing for the sake of God's name is to adjure. Therefore it is lawful to adjure the demons.
I answer that As stated in the preceding article, there are two ways of adjuring: one by way of prayer or inducement through reverence of some holy thing: the other by way of compulsion. In the first way it is not lawful to adjure the demons because such a way seems to savor of benevolence or friendship, which it is unlawful to bear towards the demons. As to the second kind of adjuration, which is by compulsion, we may lawfully use it for some purposes, and not for others. For during the course of this life the demons are our adversaries: and their actions are not subject to our disposal but to that of God and the holy angels, because, as Augustine says (De Trin. iii, 4), "the rebel spirit is ruled by the just spirit." Accordingly we may repulse the demons, as being our enemies, by adjuring them through the power of God's name, lest they do us harm of soul or body, in accord with the Divine power given by Christ, as recorded by Lc 10,19: "Behold, I have given you power to tread upon serpents and scorpions, and upon all the power of the enemy: and nothing shall hurt you."It is not, however, lawful to adjure them for the purpose of learning something from them, or of obtaining something through them, for this would amount to holding fellowship with them: except perhaps when certain holy men, by special instinct or Divine revelation, make use of the demons' actions in order to obtain certain results: thus we read of the Blessed James [*the Greater; cf. Apocrypha, N.T., Hist. Certam. Apost. vi, 19] that he caused Hermogenes to be brought to him, by the instrumentality of the demons.

Reply to Objection: 1. Origen is speaking of adjuration made, not authoritatively by way of compulsion, but rather by way of a friendly appeal.
2. Necromancers adjure and invoke the demons in order to obtain or learn something from them: and this is unlawful, as stated above. Wherefore Chrysostom, commenting on our Lord's words to the unclean spirit (Mc 1,25), "Speak no more, and go out of the man," says: "A salutary teaching is given us here, lest we believe the demons, however much they speak the truth."
3. This argument considers the adjuration whereby the demon's help is besought in doing or learning something: for this savors of fellowship with them. On the other hand, to repulse the demons by adjuring them, is to sever oneself from their fellowship.

Whether it is lawful to adjure an irrational creature?

Objection: 1. It would seem unlawful to adjure an irrational creature. An adjuration consists of spoken words. But it is useless to speak to one that understands not, such as an irrational creature. Therefore it is vain and unlawful to adjure an irrational creature.
2. Further, seemingly wherever adjuration is admissible, swearing is also admissible. But swearing is not consistent with an irrational creature. Therefore it would seem unlawful to employ adjuration towards one.
3. Further, there are two ways of adjuring, as explained above (Articles [1],2). One is by way of appeal; and this cannot be employed towards irrational creatures, since they are not masters of their own actions. The other kind of adjuration is by way of compulsion: and, seemingly, neither is it lawful to use this towards them, because we have not the power to command irrational creatures, but only He of Whom it was said (Mt 8,27): "For the winds and the sea obey Him." Therefore in no way, apparently, is it lawful to adjure irrational creatures.

On the contrary Simon and Jude are related to have adjured dragons and to have commanded them to withdraw into the desert. [*From the apocryphal Historiae Certam. Apost. vi. 19.]
I answer that Irrational creatures are directed to their own actions by some other agent. Now the action of what is directed and moved is also the action of the director and mover: thus the movement of the arrow is an operation of the archer. Wherefore the operation of the irrational creature is ascribed not only to it, but also and chiefly to God, Who disposes the movements of all things. It is also ascribed to the devil, who, by God's permission, makes use of irrational creatures in order to inflict harm on man.Accordingly the adjuration of an irrational creature may be of two kinds. First, so that the adjuration is referred to the irrational creature in itself: and in this way it would be vain to adjure an irrational creature. Secondly, so that it be referred to the director and mover of the irrational creature, and in this sense a creature of this kind may be adjured in two ways. First, by way of appeal made to God, and this relates to those who work miracles by calling on God: secondly, by way of compulsion, which relates to the devil, who uses the irrational creature for our harm. This is the kind of adjuration used in the exorcisms of the Church, whereby the power of the demons is expelled from an irrational creature. But it is not lawful to adjure the demons by beseeching them to help us.

Reply to Objection: 1. This suffices for the Replies to the Objections.


We must now consider the taking of the Divine name for the purpose of invoking it by prayer or praise. Of prayer we have already spoken (Question [83] ). Wherefore we must speak now of praise. Under this head there are two points of inquiry:

(1) Whether God should be praised with the lips?

(2) Whether God should be praised with song?

Whether God should be praised with the lips?

Objection: 1. It would seem that God should not be praised with the lips. The Philosopher says (Ethic. 1,12): "The best of men ere accorded not praise, but something greater." But God transcends the very best of all things. Therefore God ought to be given, not praise, but something greater than praise: wherefore He is said (Si 43,33) to be "above all praise."
2. Further, divine praise is part of divine worship, for it is an act of religion. Now God is worshiped with the mind rather than with the lips: wherefore our Lord quoted against certain ones the words of Is 29,13, "This people . . . honors [Vulg.: 'glorifies'] Me with their lips, but their heart is far from Me." Therefore the praise of God lies in the heart rather than on the lips.
3. Further, men are praised with the lips that they may be encouraged to do better: since just as being praised makes the wicked proud, so does it incite the good to better things. Wherefore it is written (Pr 27,21): "As silver is tried in the fining-pot . . . so a man is tried by the mouth of him that praiseth." But God is not incited to better things by man's words, both because He is unchangeable, and because He is supremely good, and it is not possible for Him to grow better. Therefore God should not be praised with the lips.

On the contrary It is written (Ps 62,6): "My mouth shall praise Thee with joyful lips."
I answer that We use words, in speaking to God, for one reason, and in speaking to man, for another reason. For when speaking to man we use words in order to tell him our thoughts which are unknown to him. Wherefore we praise a man with our lips, in order that he or others may learn that we have a good opinion of him: so that in consequence we may incite him to yet better things; and that we may induce others, who hear him praised, to think well of him, to reverence him, and to imitate him. On the other hand we employ words, in speaking to God, not indeed to make known our thoughts to Him Who is the searcher of hearts, but that we may bring ourselves and our hearers to reverence Him.Consequently we need to praise God with our lips, not indeed for His sake, but for our own sake; since by praising Him our devotion is aroused towards Him, according to Ps 49,23: "The sacrifice of praise shall glorify Me, and there is the way by which I will show him the salvation of God." And forasmuch as man, by praising God, ascends in his affections to God, by so much is he withdrawn from things opposed to God, according to Is 48,9, "For My praise I will bridle thee lest thou shouldst perish." The praise of the lips is also profitable to others by inciting their affections towards God, wherefore it is written (Ps 33,2): "His praise shall always be in my mouth," and farther on: "Let the meek hear and rejoice. O magnify the Lord with me."

Reply to Objection: 1. We may speak of God in two ways. First, with regard to His essence; and thus, since He is incomprehensible and ineffable, He is above all praise. In this respect we owe Him reverence and the honor of latria; wherefore Ps 64,2 is rendered by Jerome in his Psalter [*Translated from the Hebrew]: "Praise to Thee is speechless, O God," as regards the first, and as to the second, "A vow shall be paid to Thee." Secondly, we may speak of God as to His effects which are ordained for our good. In this respect we owe Him praise; wherefore it is written (Is 63,7): "I will remember the tender mercies of the Lord, the praise of the Lord for all the things that the Lord hath bestowed upon us." Again, Dionysius says (Div. Nom. 1): "Thou wilt find that all the sacred hymns," i.e. divine praises "of the sacred writers, are directed respectively to the Blessed Processions of the Thearchy," i.e. of the Godhead, "showing forth and praising the names of God."
2. It profits one nothing to praise with the lips if one praise not with the heart. For the heart speaks God's praises when it fervently recalls "the glorious things of His works" [*Cf. Si 17,7-8]. Yet the outward praise of the lips avails to arouse the inward fervor of those who praise, and to incite others to praise God, as stated above.
3. We praise God, not for His benefit, but for ours as stated.

Whether God should be praised with song?

Objection: 1. It would seem that God should not be praised with song. For the Apostle says (Col 3,16): "Teaching and admonishing one another in psalms, hymns and spiritual canticles." Now we should employ nothing in the divine worship, save what is delivered to us on the authority of Scripture. Therefore it would seem that, in praising God, we should employ, not corporal but spiritual canticles.
2. Further, Jerome in his commentary on Ep 5,19, "Singing and making melody in your hearts to the Lord," says: "Listen, young men whose duty it is to recite the office in church: God is to be sung not with the voice but with the heart. Nor should you, like play-actors, ease your throat and jaws with medicaments, and make the church resound with theatrical measures and airs." Therefore God should not be praised with song.
3. Further, the praise of God is competent to little and great, according to Apoc. 14, "Give praise to our God, all ye His servants; and you that fear Him, little and great." But the great, who are in the church, ought not to sing: for Gregory says (Regist. iv, ep. 44): "I hereby ordain that in this See the ministers of the sacred altar must not sing" (Cf. Decret., dist. xcii., cap. In sancta Romana Ecclesia). Therefore singing is unsuitable to the divine praises.
4. Further, in the Old Law God was praised with musical instruments and human song, according to Ps 32,2-3: "Give praise to the Lord on the harp, sing to Him with the psaltery, the instrument of ten strings. Sing to Him a new canticle." But the Church does not make use of musical instruments such as harps and psalteries, in the divine praises, for fear of seeming to imitate the Jews. Therefore in like manner neither should song be used in the divine praises.
5. Further, the praise of the heart is more important than the praise of the lips. But the praise of the heart is hindered by singing, both because the attention of the singers is distracted from the consideration of what they are singing, so long as they give all their attention to the chant, and because others are less able to understand the thing that are sung than if they were recited without chant. Therefore chants should not be employed in the divine praises.

On the contrary Blessed Ambrose established singing in the Church of Milan, a Augustine relates (Confess. ix).
I answer that As stated above (Article [1]), the praise of the voice is necessary in order to arouse man's devotion towards God. Wherefore whatever is useful in conducing to this result is becomingly adopted in the divine praises. Now it is evident that the human soul is moved in various ways according to various melodies of sound, as the Philosopher state (Polit. viii, 5), and also Boethius (De Musica, prologue). Hence the use of music in the divine praises is a salutary institution, that the souls of the faint-hearted may be the more incited to devotion. Wherefore Augustine say (Confess. x, 33): "I am inclined to approve of the usage of singing in the church, that so by the delight of the ears the faint-hearted may rise to the feeling of devotion": and he says of himself (Confess. ix, 6): "I wept in Thy hymns and canticles, touched to the quick by the voices of Thy sweet-attuned Church."

Reply to Objection: 1. The name of spiritual canticle may be given not only to those that are sung inwardly in spirit, but also to those that are sung outwardly with the lips, inasmuch as such like canticles arouse spiritual devotion.
2. Jerome does not absolutely condemn singing, but reproves those who sing theatrically in church not in order to arouse devotion, but in order to show off, or to provoke pleasure. Hence Augustine says (Confess. x, 33): "When it befalls me to be more moved by the voice than by the words sung, I confess to have sinned penally, and then had rather not hear the singer."
3. To arouse men to devotion by teaching and preaching is a more excellent way than by singing. Wherefore deacons and prelates, whom it becomes to incite men's minds towards God by means of preaching and teaching, ought not to be instant in singing, lest thereby they be withdrawn from greater things. Hence Gregory says (Regist. iv, ep. 44): "It is a most discreditable custom for those who have been raised to the diaconate to serve as choristers, for it behooves them to give their whole time to the duty of preaching and to taking charge of the alms."
4. As the Philosopher says (Polit. viii, 6), "Teaching should not be accompanied with a flute or any artificial instrument such as the harp or anything else of this kind: but only with such things as make good hearers." For such like musical instruments move the soul to pleasure rather than create a good disposition within it. In the Old Testament instruments of this description were employed, both because the people were more coarse and carnal---so that they needed to be aroused by such instruments as also by earthly promises---and because these material instruments were figures of something else.
5. The soul is distracted from that which is sung by a chant that is employed for the purpose of giving pleasure. But if the singer chant for the sake of devotion, he pays more attention to what he says, both because he lingers more thereon, and because, as Augustine remarks (Confess. x, 33), "each affection of our spirit, according to its variety, has its own appropriate measure in the voice, and singing, by some hidden correspondence wherewith it is stirred." The same applies to the hearers, for even if some of them understand not what is sung, yet they understand why it is sung, namely, for God's glory: and this is enough to arouse their devotion.

VICES OPPOSED TO RELIGION (Questions [92]-114)

Summa Th. II-II EN Qu.89 a.8