Summa Th. III EN Qu.28 a.4

Whether the Mother of God took a vow of virginity?

Objection: 1. It would seem that the Mother of God did not take a vow of virginity. For it is written (Dt 7,14): "No one shall be barren among you of either sex." But sterility is a consequence of virginity. Therefore the keeping of virginity was contrary to the commandment of the Old Law. But before Christ was born the old law was still in force. Therefore at that time the Blessed Virgin could not lawfully take a vow of virginity.
2. Further, the Apostle says (1Co 7,25): "Concerning virgins I have no commandment of the Lord; but I give counsel." But the perfection of the counsels was to take its beginning from Christ, who is the "end of the Law," as the Apostle says (Rm 10,4). It was not therefore becoming that the Virgin should take a vow of virginity.
3. Further, the gloss of Jerome says on 1Tm 5,12, that "for those who are vowed to virginity, it is reprehensible not only to marry, but also to desire to be married." But the Mother of Christ committed no sin for which she could be reprehended, as stated above (Question [27], Article [4]). Since therefore she was "espoused," as related by Lc 1,27 it seems that she did not take a vow of virginity.

On the contrary Augustine says (De Sanct. Virg. iv): "Mary answered the announcing angel: 'How shall this be done, because I know not man?' She would not have said this unless she had already vowed her virginity to God."
I answer that As we have stated in the SS, Question [88], Article [6], works of perfection are more praiseworthy when performed in fulfilment of a vow. Now it is clear that for reasons already given (Articles [1],2,3) virginity had a special place in the Mother of God. It was therefore fitting that her virginity should be consecrated to God by vow. Nevertheless because, while the Law was in force both men and women were bound to attend to the duty of begetting, since the worship of God was spread according to carnal origin, until Christ was born of that people; the Mother of God is not believed to have taken an absolute vow of virginity, before being espoused to Joseph, although she desired to do so, yet yielding her own will to God's judgment. Afterwards, however, having taken a husband, according as the custom of the time required, together with him she took a vow of virginity.

Reply to Objection: 1. Because it seemed to be forbidden by the law not to take the necessary steps for leaving a posterity on earth, therefore the Mother of God did not vow virginity absolutely, but under the condition that it were pleasing to God. When, however, she knew that it was acceptable to God, she made the vow absolute, before the angel's Annunciation.
2. Just as the fulness of grace was in Christ perfectly, yet some beginning of the fulness preceded in His Mother; so also the observance of the counsels, which is an effect of God's grace, began its perfection in Christ, but was begun after a fashion in His Virgin Mother.
3. These words of the Apostle are to be understood of those who vow chastity absolutely. Christ's Mother did not do this until she was espoused to Joseph. After her espousals, however, by their common consent she took a vow of virginity together with her spouse.


We now consider the espousals of God's Mother: concerning which two points arise for inquiry:

(1) Whether Christ should have been born of an espoused virgin?

(2) Whether there was true marriage between our Lord's Mother and Joseph?

Whether Christ should have been born of an espoused virgin?

Objection: 1. It would seem that Christ should not have been born of an espoused virgin. For espousals are ordered to carnal intercourse. But our Lord's Mother never wished to have carnal intercourse with her husband; because this would be derogatory to the virginity of her mind. Therefore she should not have been espoused.
2. Further, that Christ was born of a virgin was miraculous, whence Augustine says (Ep ad Volus. cxxxvii): "This same power of God brought forth the infant's limbs out of the virginal womb of His inviolate Mother, by which in the vigor of manhood He passed through the closed doors. If we are told why this happened, it will cease to be wonderful; if another instance be alleged, it will no longer be unique." But miracles that are wrought in confirmation of the Faith should be manifest. Since, therefore, by her Espousals this miracle would be less evident, it seems that it was unfitting that Christ should be born of an espoused virgin.
3. Further, the martyr Ignatius, as Jerome says on Mt 1,18, gives as a reason of the espousals of the Mother of God, "that the manner of His Birth might be hidden from the devil, who would think Him to be begotten not of a virgin but of a wife." But this seems to be no reason at all. First, because by his natural cunning he knows whatever takes place in bodies. Secondly, because later on the demons, through many evident signs, knew Christ after a fashion: whence it is written (Mc 1,23-24): "A man with an unclean spirit . . . cried out, saying: What have we to do with Thee, Jesus of Nazareth? Art Thou come to destroy us? I know . . . Thou art the Holy one of God." Therefore it does not seem fitting that the Mother of God should have been espoused.
4. Further, Jerome gives as another reason, "lest the Mother of God should be stoned by the Jews as an adulteress." But this reason seems to have no weight, for if she were not espoused, she could not be condemned for adultery. Therefore it does not seem reasonable that Christ should be born of an espoused virgin.

On the contrary It is written (Mt 1,18): "When as His Mother Mary was espoused to Joseph": and (Lc 1,26-27): "The angel Gabriel was sent . . . to a virgin espoused to a man whose name was Joseph."
I answer that It was fitting that Christ should be born of an espoused virgin; first, for His own sake; secondly, for His Mother's sake; thirdly, for our sake. For the sake of Christ Himself, for four reasons.First, lest He should be rejected by unbelievers as illegitimate: wherefore Ambrose says on Lc 1,26-27: "How could we blame Herod or the Jews if they seem to persecute one who was born of adultery?"Secondly, in order that in the customary way His genealogy might be traced through the male line. Thus Ambrose says on Lc 3,23: "He Who came into the world, according to the custom of the world had to be enrolled Now for this purpose, it is the men that are required, because they represent the family in the senate and other courts. The custom of the Scriptures, too, shows that the ancestry of the men is always traced out."Thirdly, for the safety of the new-born Child: lest the devil should plot serious hurt against Him. Hence Ignatius says that she was espoused "that the manner of His Birth might be hidden from the devil."Fourthly, that He might be fostered by Joseph: who is therefore called His "father," as bread-winner.It was also fitting for the sake of the Virgin. First, because thus she was rendered exempt from punishment; that is, "lest she should be stoned by the Jews as an adulteress," as Jerome says.Secondly, that thus she might be safeguarded from ill fame. Whence Ambrose says on Lc 1,26-27: "She was espoused lest she be wounded by the ill-fame of violated virginity, in whom the pregnant womb would betoken corruption."Thirdly, that, as Jerome says, Joseph might administer to her wants.This was fitting, again, for our sake. First, because Joseph is thus a witness to Christ's being born of a virgin. Wherefore Ambrose says: "Her husband is the more trustworthy witness of her purity, in that he would deplore the dishonor, and avenge the disgrace, were it not that he acknowledged the mystery."Secondly, because thereby the very words of the Virgin are rendered more credible by which she asserted her virginity. Thus Ambrose says: "Belief in Mary's words is strengthened, the motive for a lie is removed. If she had not been espoused when pregnant, she would seem to have wished to hide her sin by a lie: being espoused, she had no motive for lying, since a woman's pregnancy is the reward of marriage and gives grace to the nuptial bond." These two reasons add strength to our faith.Thirdly, that all excuse be removed from those virgins who, through want of caution, fall into dishonor. Hence Ambrose says: "It was not becoming that virgins should expose themselves to evil report, and cover themselves with the excuse that the Mother of the Lord had also been oppressed by ill-fame."Fourthly, because by this the universal Church is typified, which is a virgin and yet is espoused to one Man, Christ, as Augustine says (De Sanct. Virg. xii).A fifth reason may be added: since the Mother of the Lord being both espoused and a virgin, both virginity and wedlock are honored in her person, in contradiction to those heretics who disparaged one or the other.

Reply to Objection: 1. We must believe that the Blessed Virgin, Mother of God, desired, from an intimate inspiration of the Holy Ghost, to be espoused, being confident that by the help of God she would never come to have carnal intercourse: yet she left this to God's discretion. Wherefore she suffered nothing in detriment to her virginity.
2. As Ambrose says on Lc 1,26: "Our Lord preferred that men should doubt of His origin rather than of His Mother's purity. For he knew the delicacy of virgin modesty, and how easily the fair name of chastity is disparaged: nor did He choose that our faith in His Birth should be strengthened in detriment to His Mother." We must observe, however, that some miracles wrought by God are the direct object of faith; such are the miracles of the virginal Birth, the Resurrection of our Lord, and the Sacrament of the Altar. Wherefore our Lord wished these to be more hidden, that belief in them might have greater merit. Whereas other miracles are for the strengthening of faith: and these it behooves to be manifest.
3. As Augustine says (De Trin. iii), the devil can do many things by his natural power which he is hindered by the Divine power from doing. Thus it may be that by his natural power the devil could know that the Mother of God knew not man, but was a virgin; yet was prevented by God from knowing the manner of the Divine Birth. That afterwards the devil after a fashion knew that He was the Son of God, makes no difficulty: because then the time had already come for Christ to make known His power against the devil, and to suffer persecution aroused by him. But during His infancy it behooved the malice of the devil to be withheld, lest he should persecute Him too severely: for Christ did not wish to suffer such things then, nor to make His power known, but to show Himself to be in all things like other infants. Hence Pope Leo (Serm. in Epiph. iv) says that "the Magi found the Child Jesus small in body, dependent on others, unable to speak, and in no way differing from the generality of human infants." Ambrose, however, expounding Lc 1,26, seems to understand this of the devil's members. For, after giving the above reason---namely, that the prince of the world might be deceived---he continues thus: "Yet still more did He deceive the princes of the world, since the evil disposition of the demons easily discovers even hidden things: but those who spend their lives in worldly vanities can have no acquaintance of Divine things."
4. The sentence of adulteresses according to the Law was that they should be stoned, not only if they were already espoused or married, but also if their maidenhood were still under the protection of the paternal roof, until the day when they enter the married state. Thus it is written (Dt 22,20-21): "If . . . virginity be not found in the damsel . . . the men of the city shall stone her to death, and she shall die; because she hath done a wicked thing in Israel, to play the whore in her father's house."It may also be said, according to some writers, that the Blessed Virgin was of the family or kindred of Aaron, so that she was related to Elizabeth, as we are told (Lc 1,36). Now a virgin of the priestly tribe was condemned to death for whoredom; for we read (Lv 21,9): "If the daughter of a priest be taken in whoredom, and dishonor the name of her father, she shall be burnt with fire."Lastly, some understand the passage of Jerome to refer to the throwing of stones by ill-fame.

Whether there was a true marriage between Mary and Joseph?

Objection: 1. It would seem that there was no true marriage between Mary and Joseph. For Jerome says against Helvidius that Joseph "was Mary's guardian rather than her husband." But if this was a true marriage, Joseph was truly her husband. Therefore there was no true marriage between Mary and Joseph.
2. Further, on Mt 1,16: "Jacob begot Joseph the husband of Mary," Jerome says: "When thou readest 'husband' suspect not a marriage; but remember that Scripture is wont to speak of those who are betrothed as husband and wife." But a true marriage is not effected by the betrothal, but by the wedding. Therefore, there was no true marriage between the Blessed Virgin and Joseph.
3. Further, it is written (Mt 1,19): "Joseph, her husband, being a just man, and not willing to take her away [*Douay: 'publicly to expose her'], i.e. to take her to his home in order to cohabit with her, was minded to put her away privately, i.e. to postpone the wedding," as Remigius [*Cf. Catena Aurea in Matth.] expounds. Therefore, it seems that, as the wedding was not yet solemnized, there was no true marriage: especially since, after the marriage contract, no one can lawfully put his wife away.

On the contrary Augustine says (De Consensu Evang. ii): "It cannot be allowed that the evangelist thought that Joseph ought to sever his union with Mary" (since he said that Joseph was Mary's husband) "on the ground that in giving birth to Christ, she had not conceived of him, but remained a virgin. For by this example the faithful are taught that if after marriage they remain continent by mutual consent, their union is still and is rightly called marriage, even without intercourse of the sexes."
I answer that Marriage or wedlock is said to be true by reason of its attaining its perfection. Now perfection of anything is twofold; first, and second. The first perfection of a thing consists in its very form, from which it receives its species; while the second perfection of a thing consists in its operation, by which in some way a thing attains its end. Now the form of matrimony consists in a certain inseparable union of souls, by which husband and wife are pledged by a bond of mutual affection that cannot be sundered. And the end of matrimony is the begetting and upbringing of children: the first of which is attained by conjugal intercourse; the second by the other duties of husband and wife, by which they help one another in rearing their offspring.Thus we may say, as to the first perfection, that the marriage of the Virgin Mother of God and Joseph was absolutely true: because both consented to the nuptial bond, but not expressly to the bond of the flesh, save on the condition that it was pleasing to God. For this reason the angel calls Mary the wife of Joseph, saying to him (Mt 1,20): "Fear not to take unto thee Mary thy wife": on which words Augustine says (De Nup. et Concup. i): "She is called his wife from the first promise of her espousals, whom he had not known nor ever was to know by carnal intercourse."But as to the second perfection which is attained by the marriage act, if this be referred to carnal intercourse, by which children are begotten; thus this marriage was not consummated. Wherefore Ambrose says on Lc 1,26-27: "Be not surprised that Scripture calls Mary a wife. The fact of her marriage is declared, not to insinuate the loss of virginity, but to witness to the reality of the union." Nevertheless, this marriage had the second perfection, as to upbringing of the child. Thus Augustine says (De Nup. et Concup. i): "All the nuptial blessings are fulfilled in the marriage of Christ's parents, offspring, faith and sacrament. The offspring we know to have been the Lord Jesus; faith, for there was no adultery: sacrament, since there was no divorce. Carnal intercourse alone there was none."

Reply to Objection: 1. Jerome uses the term "husband" in reference to marriage consummated.
2. By marriage Jerome means the nuptial intercourse.
3. As Chrysostom says (Hom. i super Matth. [*Opus Imperfectum among the supposititious works ascribed to St. Chrysostom]) the Blessed Virgin was so espoused to Joseph that she dwelt in his home: "for just as she who conceives in her husband's house is understood to have conceived of him, so she who conceives elsewhere is suspect." Consequently sufficient precaution would not have been taken to safeguard the fair fame of the Blessed Virgin, if she had not the entry of her husband's house. Wherefore the words, "not willing to take her away" are better rendered as meaning, "not willing publicly to expose her," than understood of taking her to his house. Hence the evangelist adds that "he was minded to put her away privately." But although she had the entry of Joseph's house by reason of her first promise of espousals, yet the time had not yet come for the solemnizing of the wedding; for which reason they had not yet consummated the marriage. Therefore, as Chrysostom says (Hom. iv in Matth.): "The evangelist does not say, 'before she was taken to the house of her husband,' because she was already in the house. For it was the custom among the ancients for espoused maidens to enter frequently the houses of them to whom they were betrothed." Therefore the angel also said to Joseph: "Fear not to take unto thee Mary thy wife"; that is: "Fear not to solemnize your marriage with her." Others, however, say that she was not yet admitted to his house, but only betrothed to him. But the first is more in keeping with the Gospel narrative.


We now have to consider the Blessed Virgin's Annunciation, concerning which there are four points of inquiry:

(1) Whether it was befitting that announcement should be made to her of that which was to be begotten of her?

(2) By whom should this announcement be made?

(3) In what manner should this announcement be made?

(4) Of the order observed in the Annunciation.

Whether it was necessary to announce to the Blessed Virgin that which was to be done in her?

Objection: 1. It would seem that it was unnecessary to announce to the Blessed Virgin that which was to be done in her. For there seems to have been no need of the Annunciation except for the purpose of receiving the Virgin's consent. But her consent seems to have been unnecessary: because the Virginal Conception was foretold by a prophecy of "predestination," which is "fulfilled without our consent," as a gloss says on Mt 1,22. There was no need, therefore, for this Annunciation.
2. Further, the Blessed Virgin believed in the Incarnation, for to disbelieve therein excludes man from the way of salvation; because, as the Apostle says (Rm 3,22): "The justice of God (is) by faith of Jesus Christ." But one needs no further instruction concerning what one believes without doubt. Therefore the Blessed Virgin had no need for the Incarnation of her Son to be announced to her.
3. Further, just as the Blessed Virgin conceived Christ in her body, so every pious soul conceives Him spiritually. Thus the Apostle says (Ga 4,19): "My little children, of whom I am in labor again, until Christ be formed in you." But to those who conceive Him spiritually no announcement is made of this conception. Therefore neither should it have been announced to the Blessed Virgin that she was to conceive the Son of God in her womb.

On the contrary It is related (Lc 1,31) that the angel said to her: "Behold, thou shalt conceive in thy womb, and shalt bring forth a son."
I answer that It was reasonable that it should be announced to the Blessed Virgin that she was to conceive Christ. First, in order to maintain a becoming order in the union of the Son of God with the Virgin---namely, that she should be informed in mind concerning Him, before conceiving Him in the flesh. Thus Augustine says (De Sancta Virgin. iii): "Mary is more blessed in receiving the faith of Christ, than in conceiving the flesh of Christ"; and further on he adds: "Her nearness as a Mother would have been of no profit to Mary, had she not borne Christ in her heart after a more blessed manner than in her flesh."Secondly, that she might be a more certain witness of this mystery, being instructed therein by God.Thirdly, that she might offer to God the free gift of her obedience: which she proved herself right ready to do, saying: "Behold the handmaid of the Lord."Fourthly, in order to show that there is a certain spiritual wedlock between the Son of God and human nature. Wherefore in the Annunciation the Virgin's consent was besought in lieu of that of the entire human nature.

Reply to Objection: 1. The prophecy of predestination is fulfilled without the causality of our will; not without its consent.
2. The Blessed Virgin did indeed believe explicitly in the future Incarnation; but, being humble, she did not think such high things of herself. Consequently she required instruction in this matter.
3. The spiritual conception of Christ through faith is preceded by the preaching of the faith, for as much as "faith is by hearing" (Rm 10,17). Yet man does not know for certain thereby that he has grace; but he does know that the faith, which he has received, is true.

Whether the annunciation should have been made by an angel to the Blessed Virgin?

Objection: 1. It would seem that the Annunciation should not have been made by an angel to our Blessed Lady. For revelations to the highest angels are made immediately by God, as Dionysius says (Coel. Hier. vii). But the Mother of God is exalted above all the angels. Therefore it seems that the mystery of the Incarnation should have been announced to her by God immediately, and not by an angel.
2. Further, if in this matter it behooved the common order to be observed, by which Divine things are announced to men by angels; in like manner Divine things are announced to a woman by a man: wherefore the Apostle says (1Co 14,34-35): "Let women keep silence in the churches . . . but if they would learn anything, let them ask their husbands at home." Therefore it seems that the mystery of the Incarnation should have been announced to the Blessed Virgin by some man: especially seeing that Joseph, her husband, was instructed thereupon by an angel, as is related (Mt 1,20-21)
3. Further, none can becomingly announce what he knows not. But the highest angels did not fully know the mystery of the Incarnation: wherefore Dionysius says (Coel. Hier. vii) that the question, "Who is this that cometh from Edom?" (Is 63,1) is to be understood as made by them. Therefore it seems that the announcement of the Incarnation could not be made becomingly by any angel.
4. Further, greater things should be announced by messengers of greater dignity. But the mystery of the Incarnation is the greatest of all things announced by angels to men. It seems, therefore, if it behooved to be announced by an angel at all, that this should have been done by an angel of the highest order. But Gabriel is not of the highest order, but of the order of archangels, which is the last but one: wherefore the Church sings: "We know that the archangel Gabriel brought thee a message from God" [*Feast of Purification B.V.M. ix Resp. Brev. O.P.]. Therefore this announcement was not becomingly made by the archangel Gabriel.

On the contrary It is written (Lc 1,26): "The angel Gabriel was sent by God," etc.
I answer that It was fitting for the mystery of the Incarnation to be announced to the Mother of God by an angel, for three reasons. First, that in this also might be maintained the order established by God, by which Divine things are brought to men by means of the angels. Wherefore Dionysius says (Coel. Hier. iv) that "the angels were the first to be taught the Divine mystery of the loving kindness of Jesus: afterwards the grace of knowledge was imparted to us through them. Thus, then, the most god-like Gabriel made known to Zachary that a prophet son would be born to him; and, to Mary, how the Divine mystery of the ineffable conception of God would be realized in her."Secondly, this was becoming to the restoration of human nature which was to be effected by Christ. Wherefore Bede says in a homily (in Annunt.): "It was an apt beginning of man's restoration that an angel should be sent by God to the Virgin who was to be hallowed by the Divine Birth: since the first cause of man's ruin was through the serpent being sent by the devil to cajole the woman by the spirit of pride."Thirdly, because this was becoming to the virginity of the Mother of God. Wherefore Jerome says in a sermon on the Assumption [*Ascribed to St. Jerome but not his work]: "It is well that an angel be sent to the Virgin; because virginity is ever akin to the angelic nature. Surely to live in the flesh and not according to the flesh is not an earthly but a heavenly life."

Reply to Objection: 1. The Mother of God was above the angels as regards the dignity to which she was chosen by God. But as regards the present state of life, she was beneath the angels. For even Christ Himself, by reason of His passible life, "was made a little lower than the angels," according to He 2,9. But because Christ was both wayfarer and comprehensor, He did not need to be instructed by angels, as regards knowledge of Divine things. The Mother of God, however, was not yet in the state of comprehension: and therefore she had to be instructed by angels concerning the Divine Conception.
2. As Augustine says in a sermon on the Assumption (De Assump. B.V.M. [*Work of another author: among the works of St. Augustine]) a true estimation of the Blessed Virgin excludes her from certain general rules. For "neither did she 'multiply her conceptions' nor was she 'under man's, i.e. her husband's,' power (Gn 3,16), who in her spotless womb conceived Christ of the Holy Ghost." Therefore it was fitting that she should be informed of the mystery of the Incarnation by means not of a man, but of an angel. For this reason it was made known to her before Joseph: since the message was brought to her before she conceived, but to Joseph after she had conceived.
3. As may be gathered from the passage quoted from Dionysius, the angels were acquainted with the mystery of the Incarnation: and yet they put this question, being desirous that Christ should give them more perfect knowledge of the details of this mystery, which are incomprehensible to any created intellect. Thus Maximus [*Maximus of Constantinople] says that "there can be no question that the angels knew that the Incarnation was to take place. But it was not given to them to trace the manner of our Lord's conception, nor how it was that He remained whole in the Father, whole throughout the universe, and was whole in the narrow abode of the Virgin."
4. Some say that Gabriel was of the highest order; because Gregory says (Hom. de Centum Ovibus [*34 in Evang.]): "It was right that one of the highest angels should come, since his message was most sublime." But this does nat imply that he was of the highest order of all, but in regard to the angels: since he was an archangel. Thus the Church calls him an archangel, and Gregory himself in a homily (De Centum Ovibus 34) says that "those are called archangels who announce sublime things." It is therefore sufficiently credible that he was the highest of the archangels. And, as Gregory says (De Centum Ovibus 34), this name agrees with his office: for "Gabriel means 'Power of God.' This message therefore was fittingly brought by the 'Power of God,' because the Lord of hosts and mighty in battle was coming to overcome the powers of the air."

Whether the angel of annunciation should have appeared to the Virgin in a bodily vision?

Objection: 1. It would seem that the angel of the Annunciation should not have appeared to the Virgin in a bodily vision. For "intellectual vision is more excellent than bodily vision," as Augustine says (Gn ad lit. xii), and especially more becoming to an angel: since by intellectual vision an angel is seen in his substance; whereas in a bodily vision he is seen in the bodily shape which he assumes. Now since it behooved a sublime messenger to come to announce the Divine Conception, so, seemingly, he should have appeared in the most excellent kind of vision. Therefore it seems that the angel of the Annunciation appeared to the Virgin in an intellectual vision.
2. Further, imaginary vision also seems to excel bodily vision: just as the imagination is a higher power than the senses. But "the angel . . . appeared to Joseph in his sleep" (Mt 1,20), which was clearly an imaginary vision. Therefore it seems that he should have appeared to the Blessed Virgin also in an imaginary vision.
3. Further, the bodily vision of a spiritual substance stupefies the beholder; thus we sing of the Virgin herself: "And the Virgin seeing the light was filled with fear" [*Feast of Annunciation, B.V.M. ii Resp. Brev. O.P.]. But it was better that her mind should be preserved from being thus troubled. Therefore it was not fitting that this announcement should be made in a bodily vision.

On the contrary Augustine in a sermon (De Annunt. iii) pictures the Blessed Virgin as speaking thus: "To me came the archangel Gabriel with glowing countenance, gleaming robe, and wondrous step." But these cannot pertain to other than bodily vision. Therefore the angel of the Annunciation appeared in a bodily vision to the Blessed Virgin.
I answer that The angel of the Annunciation appeared in a bodily vision to the Blessed Virgin. And this indeed was fitting, first in regard to that which was announced. For the angel came to announce the Incarnation of the invisible God. Wherefore it was becoming that, in order to make this known, an invisible creature should assume a form in which to appear visibly: forasmuch as all the apparitions of the Old Testament are ordered to that apparition in which the Son of God appeared in the flesh.Secondly, it was fitting as regards the dignity of the Mother of God, who was to receive the Son of God not only in her mind, but in her bodily womb. Therefore it behooved not only her mind, but also her bodily senses to be refreshed by the angelic vision.Thirdly, it is in keeping with the certainty of that which was announced. For we apprehend with greater certainty that which is before our eyes, than what is in our imagination. Thus Chrysostom says (Hom. iv in Matth.) that the angel "came to the Virgin not in her sleep, but visibly. For since she was receiving from the angel a message exceeding great, before such an event she needed a vision of great solemnity."

Reply to Objection: 1. Intellectual vision excels merely imaginary and merely bodily vision. But Augustine himself says (De Annunt. iii) that prophecy is more excellent if accompanied by intellectual and imaginary vision, than if accompanied by only one of them. Now the Blessed Virgin perceived not only the bodily vision, but also the intellectual illumination. Wherefore this was a more excellent vision. Yet it would have been more excellent if she had perceived the angel himself in his substance by her intellectual vision. But it was incompatible with her state of wayfarer that she should see an angel in his essence.
2. The imagination is indeed a higher power than the exterior sense: but because the senses are the principle of human knowledge, the greatest certainty is in them, for the principles of knowledge must needs always be most certain. Consequently Joseph, to whom the angel appeared in his sleep, did not have so excellent a vision as the Blessed Virgin.
3. As Ambrose says on Lc 1,11: "We are disturbed, and lose our presence of mind, when we are confronted by the presence of a superior power." And this happens not only in bodily, but also in imaginary vision. Wherefore it is written (Gn 15,12) that "when the sun was setting, a deep sleep fell upon Abram, and a great and darksome horror seized upon him." But by being thus disturbed man is not harmed to such an extent that therefore he ought to forego the vision of an angel. First because from the very fact that man is raised above himself, in which matter his dignity is concerned, his inferior powers are weakened; and from this results the aforesaid disturbance: thus, also, when the natural heat is drawn within a body, the exterior parts tremble. Secondly, because, as Origen says (Hom. iv in Lc.): "The angel who appeared, knowing hers was a human nature, first sought to remedy the disturbance of mind to which a man is subject." Wherefore both to Zachary and to Mary, as soon as they were disturbed, he said: "Fear not." For this reason, as we read in the life of Anthony, "it is difficult to discern good from evil spirits. For if joy succeed fear, we should know that the help is from the Lord: because security of soul is a sign of present majesty. But if the fear with which we are stricken persevere, it is an enemy that we see."Moreover it was becoming to virginal modesty that the Virgin should be troubled. Because, as Ambrose says on Lc 1,20: "It is the part of a virgin to be timid, to fear the advances of men, and to shrink from men's addresses."But others says that as the Blessed Virgin was accustomed to angelic visions, she was not troubled at seeing this angel, but with wonder at hearing what the angel said to her, for she did not think so highly of herself. Wherefore the evangelist does not say that she was troubled at seeing the angel, but "at his saying."

Summa Th. III EN Qu.28 a.4