Obj. 6: Further, Thrones are seats. But from the fact that God knows and loves the rational creature He is said to sit within it. Therefore there ought not to be any order of "Thrones" besides the "Cherubim" and "Seraphim." Therefore it appears that the orders of angels are not properly styled.
On the contrary is the authority of Holy Scripture wherein they are so named. For the name "Seraphim" is found in Isa. 6:2; the name "Cherubim" in Ezech. 1 (Cf. 10:15,20); "Thrones" in Col. 1:16; "Dominations," "Virtues," "Powers," and "Principalities" are mentioned in Eph. 1:21; the name "Archangels" in the canonical epistle of St. Jude (9), and the name "Angels" is found in many places of Scripture.
I answer that, As Dionysius says (Coel. Hier. vii), in the names of the angelic orders it is necessary to observe that the proper name of each order expresses its property. Now to see what is the property of each order, we must consider that in coordinated things, something may be found in a threefold manner: by way of property, by way of excess, and by way of participation. A thing is said to be in another by way of property, if it is adequate and proportionate to its nature: by excess when an attribute is less than that to which it is attributed, but is possessed thereby in an eminent manner, as we have stated (Q. 13, A. 2) concerning all the names which are attributed to God: by participation, when an attribute is possessed by something not fully but partially; thus holy men are called gods by participation. Therefore, if anything is to be called by a name designating its property, it ought not to be named from what it participates imperfectly, nor from that which it possesses in excess, but from that which is adequate thereto; as, for instance, when we wish properly to name a man, we should call him a "rational substance," but not an "intellectual substance," which latter is the proper name of an angel; because simple intelligence belongs to an angel as a property, and to man by participation; nor do we call him a "sensible substance," which is the proper name of a brute; because sense is less than the property of a man, and belongs to man in a more excellent way than to other animals.
So we must consider that in the angelic orders all spiritual perfections are common to all the angels, and that they are all more excellently in the superior than in the inferior angels. Further, as in these perfections there are grades, the superior perfection belongs to the superior order as its property, whereas it belongs to the inferior by participation; and conversely the inferior perfection belongs to the inferior order as its property, and to the superior by way of excess; and thus the superior order is denominated from the superior perfection.
So in this way Dionysius (Coel. Hier. vii) explains the names of the orders accordingly as they befit the spiritual perfections they signify. Gregory, on the other hand, in expounding these names (Hom. xxxiv in Evang.) seems to regard more the exterior ministrations; for he says that "angels are so called as announcing the least things; and the archangels in the greatest; by the virtues miracles are wrought; by the powers hostile powers are repulsed; and the principalities preside over the good spirits themselves."
Reply Obj. 1: Angel means "messenger." So all the heavenly spirits, so far as they make known Divine things, are called "angels." But the superior angels enjoy a certain excellence, as regards this manifestation, from which the superior orders are denominated. The lowest order of angels possess no excellence above the common manifestation; and therefore it is denominated from manifestation only; and thus the common name remains as it were proper to the lowest order, as Dionysius says (Coel. Hier. v). Or we may say that the lowest order can be specially called the order of "angels," forasmuch as they announce things to us immediately.
"Virtue" can be taken in two ways. First, commonly, considered as the medium between the essence and the operation, and in that sense all the heavenly spirits are called heavenly virtues, as also "heavenly essences." Secondly, as meaning a certain excellence of strength; and thus it is the proper name of an angelic order. Hence Dionysius says (Coel. Hier. viii) that the "name 'virtues' signifies a certain virile and immovable strength"; first, in regard of those Divine operations which befit them; secondly, in regard to receiving Divine gifts. Thus it signifies that they undertake fearlessly the Divine behests appointed to them; and this seems to imply strength of mind.
Reply Obj. 2: As Dionysius says (Div. Nom. xii): "Dominion is attributed to God in a special manner, by way of excess: but the Divine word gives the more illustrious heavenly princes the name of Lord by participation, through whom the inferior angels receive the Divine gifts." Hence Dionysius also states (Coel. Hier. viii) that the name "Domination" means first "a certain liberty, free from servile condition and common subjection, such as that of plebeians, and from tyrannical oppression," endured sometimes even by the great. Secondly, it signifies "a certain rigid and inflexible supremacy which does not bend to any servile act, or to the act of those who are subject to or oppressed by tyrants." Thirdly, it signifies "the desire and participation of the true dominion which belongs to God." Likewise the name of each order signifies the participation of what belongs to God; as the name "Virtues" signifies the participation of the Divine virtue; and the same principle applies to the rest.
Reply Obj. 3: The names "Domination," "Power," and "Principality" belong to government in different ways. The place of a lord is only to prescribe what is to be done. So Gregory says (Hom. xxiv in Evang.), that "some companies of the angels, because others are subject to obedience to them, are called dominations." The name "Power" points out a kind of order, according to what the Apostle says, "He that resisteth the power, resisteth the ordination of God" (Rom. 13:2). And so Dionysius says (Coel. Hier. viii) that the name "Power" signifies a kind of ordination both as regards the reception of Divine things, and as regards the Divine actions performed by superiors towards inferiors by leading them to things above. Therefore, to the order of "Powers" it belongs to regulate what is to be done by those who are subject to them. To preside [principari] as Gregory says (Hom. xxiv in Ev.) is "to be first among others," as being first in carrying out what is ordered to be done. And so Dionysius says (Coel. Hier. ix) that the name of "Principalities" signifies "one who leads in a sacred order." For those who lead others, being first among them, are properly called "princes," according to the words, "Princes went before joined with singers" (Ps. 67:26).
Reply Obj. 4: The "Archangels," according to Dionysius (Coel. Hier. ix), are between the "Principalities" and the "Angels." A medium compared to one extreme seems like the other, as participating in the nature of both extremes; thus tepid seems cold compared to hot, and hot compared to cold. So the "Archangels" are called the "angel princes"; forasmuch as they are princes as regards the "Angels," and angels as regards the Principalities. But according to Gregory (Hom. xxiv in Ev.) they are called "Archangels," because they preside over the one order of the "Angels"; as it were, announcing greater things: and the "Principalities" are so called as presiding over all the heavenly "Virtues" who fulfil the Divine commands.