But although one city thus comprises several orders, all may be reduced to three, when we consider that every multitude has a beginning, a middle, and an end. So in every city, a threefold order of men is to be seen, some of whom are supreme, as the nobles; others are the last, as the common people, while others hold a place between these, as the middle-class [populus honorabilis]. In the same way we find in each angelic hierarchy the orders distinguished according to their actions and offices, and all this diversity is reduced to three—namely, to the summit, the middle, and the base; and so in every hierarchy Dionysius places three orders (Coel. Hier. vi).
Reply Obj. 1: Order is twofold. In one way it is taken as the order comprehending in itself different grades; and in that way a hierarchy is called an order. In another way one grade is called an order; and in that sense the several orders of one hierarchy are so called.
Reply Obj. 2: All things are possessed in common by the angelic society, some things, however, being held more excellently by some than by others. Each gift is more perfectly possessed by the one who can communicate it, than by the one who cannot communicate it; as the hot thing which can communicate heat is more perfect that what is unable to give heat. And the more perfectly anyone can communicate a gift, the higher grade he occupies, as he is in the more perfect grade of mastership who can teach a higher science. By this similitude we can reckon the diversity of grades or orders among the angels, according to their different offices and actions.
Reply Obj. 3: The inferior angel is superior to the highest man of our hierarchy, according to the words, "He that is the lesser in the kingdom of heaven, is greater than he"—namely, John the Baptist, than whom "there hath not risen a greater among them that are born of women" (Matt. 11:11). Hence the lesser angel of the heavenly hierarchy can not only cleanse, but also enlighten and perfect, and in a higher way than can the orders of our hierarchy. Thus the heavenly orders are not distinguished by reason of these, but by reason of other different acts. _______________________
THIRD ARTICLE [I, Q. 108, Art. 3]
Whether There Are Many Angels in One Order?
Objection 1: It seems that there are not many angels in one order. For it was shown above (Q. 50, A. 4), that all the angels are unequal. But equals belong to one order. Therefore there are not many angels in one order.
Obj. 2: Further, it is superfluous for a thing to be done by many, which can be done sufficiently by one. But that which belongs to one angelic office can be done sufficiently by one angel; so much more sufficiently than the one sun does what belongs to the office of the sun, as the angel is more perfect than a heavenly body. If, therefore, the orders are distinguished by their offices, as stated above (A. 2), several angels in one order would be superfluous.
Obj. 3: Further, it was said above (Obj. 1) that all the angels are unequal. Therefore, if several angels (for instance, three or four), are of one order, the lowest one of the superior order will be more akin to the highest of the inferior order than with the highest of his own order; and thus he does not seem to be more of one order with the latter than with the former. Therefore there are not many angels of one order.
On the contrary, It is written: "The Seraphim cried to one another" (Isa. 6:3). Therefore there are many angels in the one order of the Seraphim.