On the contrary, Jerome says (vide A, 4) that "each soul has an angel appointed to guard it from its birth."
I answer that, as Origen observes (Tract. v, super Matt.) there are two opinions on this matter. For some have held that the angel guardian is appointed at the time of baptism, others, that he is appointed at the time of birth. The latter opinion Jerome approves (vide A, 4), and with reason. For those benefits which are conferred by God on man as a Christian, begin with his baptism; such as receiving the Eucharist, and the like. But those which are conferred by God on man as a rational being, are bestowed on him at his birth, for then it is that he receives that nature. Among the latter benefits we must count the guardianship of angels, as we have said above (AA[1],4). Wherefore from the very moment of his birth man has an angel guardian appointed to him.
Reply to Objection 1: Angels are sent to minister, and that efficaciously indeed, for those who shall receive the inheritance of salvation, if we consider the ultimate effect of their guardianship, which is the realizing of that inheritance. But for all that, the angelic ministrations are not withdrawn for others although they are not so efficacious as to bring them to salvation: efficacious, nevertheless, they are, inasmuch as they ward off many evils.
Reply to Objection 2: Guardianship is ordained to enlightenment by instruction, as to its ultimate and principal effect. Nevertheless it has many other effects consistent with childhood; for instance to ward off the demons, and to prevent both bodily and spiritual harm.
Reply to Objection 3: As long as the child is in the mother's womb it is not entirely separate, but by reason of a certain intimate tie, is still part of her: just as the fruit while hanging on the tree is part of the tree. And therefore it can be said with some degree of probability, that the angel who guards the mother guards the child while in the womb. But at its birth, when it becomes separate from the mother, an angel guardian is appointed to it; as Jerome, above quoted, says.
Whether the angel guardian ever forsakes a man?
Objection 1: It would seem that the angel guardian sometimes forsakes the man whom he is appointed to guard. For it is said ( Jer. 51:9 ) in the person of the angels: "We would have cured Babylon, but she is not healed: let us forsake her." And ( Is. 5:5 ) it is written: "I will take away the hedge"---that is, "the guardianship of the angels" [gloss]---"and it shall be wasted."
Objection 2: Further, God's guardianship excels that of the angels. But God forsakes man at times, according to Ps. 21:2 : "O God, my God, look upon me: why hast Thou forsaken me?" Much rather therefore does an angel guardian forsake man.
Objection 3: Further, according to Damascene (De Fide Orth. ii, 3), "When the angels are here with us, they are not in heaven." But sometimes they are in heaven. Therefore sometimes they forsake us.
On the contrary, The demons are ever assailing us, according to 1 Pet. 5:8 : "Your adversary the devil, as a roaring lion, goeth about, seeking whom he may devour." Much more therefore do the good angels ever guard us.
I answer that, As appears above (A[2]), the guardianship of the angels is an effect of Divine providence in regard to man. Now it is evident that neither man, nor anything at all, is entirely withdrawn from the providence of God: for in as far as a thing participates being, so far is it subject to the providence that extends over all being. God indeed is said to forsake man, according to the ordering of His providence, but only in so far as He allows man to suffer some defect of punishment or of fault. In like manner it must be said that the angel guardian never forsakes a man entirely, but sometimes he leaves him in some particular, for instance by not preventing him from being subject to some trouble, or even from falling into sin, according to the ordering of Divine judgments. In this sense Babylon and the House of Israel are said to have been forsaken by the angels, because their angel guardians did not prevent them from being subject to tribulation.
From this the answers are clear to the first and second objections.
Reply to Objection 3: Although an angel may forsake a man sometimes locally, he does not for that reason forsake him as to the effect of his guardianship: for even when he is in heaven he knows what is happening to man; nor does he need time for his local motion, for he can be with man in an instant.
Whether angels grieve for the ills of those whom they guard?
Objection 1: It would seem that angels grieve for the ills of those whom they guard. For it is written ( Is. 33:7 ): "The angels of peace shall weep bitterly." But weeping is a sign of grief and sorrow. Therefore angels grieve for the ills of those whom they guard.
Objection 2: Further, according to Augustine (De Civ. Dei xiv, 15), "sorrow is for those things that happen against our will." But the loss of the man whom he has guarded is against the guardian angel's will. Therefore angels grieve for the loss of men.
Objection 3: Further, as sorrow is contrary to joy, so penance is contrary to sin. But angels rejoice about one sinner doing penance, as we are told, Lk. 15:7. Therefore they grieve for the just man who falls into sin.
Objection 4: Further, on Numbers 18:12 : "Whatsoever first-fruits they offer," etc. the gloss of Origen says: "The angels are brought to judgment as to whether men have fallen through their negligence or through their own fault." But it is reasonable for anyone to grieve for the ills which have brought him to judgment. Therefore angels grieve for men's sins.
On the contrary, Where there is grief and sorrow, there is not perfect happiness: wherefore it is written ( Apoc. 21:4 ): "Death shall be no more, nor mourning, nor crying, nor sorrow." But the angels are perfectly happy. Therefore they have no cause for grief.
I answer that, Angels do not grieve, either for sins or for the pains inflicted on men. For grief and sorrow, according to Augustine (De Civ. Dei xiv, 15) are for those things which occur against our will. But nothing happens in the world contrary to the will of the angels and the other blessed, because they will cleaves entirely to the ordering of Divine justice; while nothing happens in the world save what is effected or permitted by Divine justice. Therefore simply speaking, nothing occurs in the world against the will of the blessed. For as the Philosopher says (Ethic. iii, 1) that is called simply voluntary, which a man wills in a particular case, and at a particular time, having considered all the circumstances; although universally speaking, such a thing would not be voluntary: thus the sailor does not will the casting of his cargo into the sea, considered universally and absolutely, but on account of the threatened danger of his life, he wills it. Wherefore this is voluntary rather than involuntary, as stated in the same passage. Therefore universally and absolutely speaking the angels do not will sin and the pains inflicted on its account: but they do will the fulfilment of the ordering of Divine justice in this matter, in respect of which some are subjected to pains and are allowed to fall into sin.
Reply to Objection 1: These words of Isaias may be understood of the angels, i.e. the messengers, of Ezechias, who wept on account of the words of Rabsaces, as related Is. 37:2 seqq.: this would be the literal sense. According to the allegorical sense the "angels of peace" are the apostles and preachers who weep for men's sins. If according to the anagogical sense this passage be expounded of the blessed angels, then the expression is metaphorical, and signifies that universally speaking the angels will the salvation of mankind: for in this sense we attribute passions to God and the angels.
The reply to the second objection appears from what has been said.
Reply to Objection 3: Both in man's repentance and in man's sin there is one reason for the angel's joy, namely the fulfilment of the ordering of the Divine Providence.
Reply to Objection 4: The angels are brought into judgment for the sins of men, not as guilty, but as witnesses to convict man of weakness.
Whether there can be strife or discord among the angels?