Objection 1: It would seem that we ought not to distinguish several orders. For the greater a power is, the less is it multiplied. Now this sacrament ranks above the others insofar as it places its recipients in a degree above other persons. Since, then, the other sacraments are not divided into several of which the whole is predicated, neither ought this sacrament to be divided into several orders.

Obj. 2: Furthermore, if it is divided, either it is a division of the whole into integral parts or into subjective parts. It is not in integral parts, for then they would not receive the predication of the whole. Therefore, it is a division into subjective parts. But subjective parts receive in the plural the predication of the remote genus as well as proximate genus, as man and ass are several animals, and several animate bodies. Therefore also, the priesthood and diaconate are like several orders; so also, several sacraments, since sacrament is as the genus for holy orders.

Obj. 3: Further, according to the Philosopher (Ethics 8.10) the form of authority in which one alone governs is a better government of the common good than aristocracy, where different persons occupy different offices. But the government of the Church should be the best of all. Therefore, in the Church there should be no distinction of orders for different acts, but the whole power should reside in one person; and consequently there ought to be only one order.

On the contrary, The Church is Christ’s mystical body, like to our natural body, according to the Apostle. (Cf. Rom 12:5; 1 Cor 12:12–27; Eph 1:22–23; Col 1:24) Now in the natural body there are various offices of the members. Therefore, in the Church also there should be various orders.

Further, The ministry of the New Testament is superior to that of the Old Testament (2 Cor 3). Now in the Old Testament not only the priests, but also their ministers, the Levites, were consecrated. Therefore, likewise in the New Testament not only the priests but also their ministers should be consecrated by the sacrament of order; and consequently there ought to be several orders.

I answer that, Multiplicity of orders was introduced into the Church for three reasons. First, to show forth the wisdom of God, which is reflected in the orderly distinction of things both natural and spiritual. This is signified in the statement that when the queen of Sheba saw the order of Solomon’s servants she had no longer any spirit in her (1 Kgs 10:4–5), for she was breathless from admiration of his wisdom.

Second, in order to succor human weakness, because it would be impossible for one man, without his being heavily burdened, to fulfill all things pertaining to the divine mysteries; and so various orders are severally appointed to the various offices; and this is shown by the Lord giving Moses seventy ancients to assist him (Num 11:16).

Third, so that a path for advancing further might be given to men when they distribute more people among different offices so that all may be God’s cooperators, than which nothing is more divine, as Dionysius says (On the Ecclesiastical Hierarchies 3).

Reply Obj. 1: The other sacraments are given that certain effects may be received; but this sacrament is given chiefly that certain acts may be performed. Hence the sacrament of holy orders ought to be differentiated according to the diversity of acts, even as powers are differentiated by their acts.

Reply Obj. 2: The division of holy orders is not that of an integral whole into its parts, nor of a universal whole, but of a potential whole, the nature of which is that the notion of the whole is found to be complete in one part, but in the others by some participation thereof. Thus it is here: for the entire fullness of the sacrament is in one order, namely, the priesthood, while in the other sacraments there is a participation of holy orders. And this is signified by the Lord saying: I will take of your spirit and give to them, that they may bear with you the burden of the people (Num 11:17). Therefore, all the orders are one sacrament.

Reply Obj. 3: In a kingdom, although the entire fullness of power resides in the king, this does not exclude the ministers having a power which is a participation of the kingly power. It is the same in holy orders. In the aristocratic form of government, on the contrary, the fullness of power resides in no one, but in all.