Objection 1. It would seem that men are not taken up into the orders of the angels. For the human hierarchy is stationed beneath the lowest heavenly hierarchy, as the lowest under the middle hierarchy and the middle beneath the first. But the angels of the lowest hierarchy are never transferred into the middle, or the first. Therefore neither are men transferred to the angelic orders.
Objection 2. Further, certain offices belong to the orders of the angels, as to guard, to work miracles, to coerce the demons, and the like; which do not appear to belong to the souls of the saints. Therefore they are not transferred to the angelic orders.
Objection 3. Further, as the good angels lead on to good, so do the demons to what is evil. But it is erroneous to say that the souls of bad men are changed into demons; for Chrysostom rejects this (Hom. xxviii in Matt.). Therefore it does not seem that the souls of the saints will be transferred to the orders of angels.
On the contrary, The Lord says of the saints that, "they will be as the angels of God" (Matthew 22:30).
I answer that, As above explained (4,7), the orders of the angels are distinguished according to the conditions of nature and according to the gifts of grace. Considered only as regards the grade of nature, men can in no way be assumed into the angelic orders; for the natural distinction will always remain. In view of this distinction, some asserted that men can in no way be transferred to an equality with the angels; but this is erroneous, contradicting as it does the promise of Christ saying that the children of the resurrection will be equal to the angels in heaven (Luke 20:36). For whatever belongs to nature is the material part of an order; whilst that which perfects is from grace which depends on the liberality of God, and not on the order of nature. Therefore by the gift of grace men can merit glory in such a degree as to be equal to the angels, in each of the angelic grades; and this implies that men are taken up into the orders of the angels. Some, however, say that not all who are saved are assumed into the angelic orders, but only virgins or the perfect; and that the other will constitute their own order, as it were, corresponding to the whole society of the angels. But this is against what Augustine says (De Civ. Dei xii, 9), that "there will not be two societies of men and angels, but only one; because the beatitude of all is to cleave to God alone."
Reply to Objection 1. Grace is given to the angels in proportion to their natural gifts. This, however, does not apply to men, as above explained (4; 62, 6). So, as the inferior angels cannot be transferred to the natural grade of the superior, neither can they be transferred to the superior grade of grace; whereas men can ascend to the grade of grace, but not of nature.
Reply to Objection 2. The angels according to the order of nature are between us and God; and therefore according to the common law not only human affairs are administered by them, but also all corporeal matters. But holy men even after this life are of the same nature with ourselves; and hence according to the common law they do not administer human affairs, "nor do they interfere in the things of the living," as Augustine says (De cura pro mortuis xiii, xvi). Still, by a certain special dispensation it is sometimes granted to some of the saints to exercise these offices; by working miracles, by coercing the demons, or by doing something of that kind, as Augustine says (De cura pro mortuis xvi).
Reply to Objection 3. It is not erroneous to say that men are transferred to the penalty of demons; but some erroneously stated that the demons are nothing but souls of the dead; and it is this that Chrysostom rejects.
Source: Summa Theologica (New Advent)