Reply Obj. 2: Counsel is a kind of inquiry: hence it must proceed from some principles. Nor is it enough for it to proceed from principles imparted by nature, which are the precepts of the natural law, for the reasons given above: but there is need for certain additional principles, namely, the precepts of the Divine law.
Reply Obj. 3: Irrational creatures are not ordained to an end higher than that which is proportionate to their natural powers: consequently the comparison fails. ________________________
FIFTH ARTICLE [I-II, Q. 91, Art. 5]
Whether There Is but One Divine Law?
Objection 1: It would seem that there is but one Divine law. Because, where there is one king in one kingdom there is but one law. Now the whole of mankind is compared to God as to one king, according to Ps. 46:8: "God is the King of all the earth." Therefore there is but one Divine law.
Obj. 2: Further, every law is directed to the end which the lawgiver intends for those for whom he makes the law. But God intends one and the same thing for all men; since according to 1 Tim. 2:4: "He will have all men to be saved, and to come to the knowledge of the truth." Therefore there is but one Divine law.
Obj. 3: Further, the Divine law seems to be more akin to the eternal law, which is one, than the natural law, according as the revelation of grace is of a higher order than natural knowledge. Therefore much more is the Divine law but one.
On the contrary, The Apostle says (Heb. 7:12): "The priesthood being translated, it is necessary that a translation also be made of the law." But the priesthood is twofold, as stated in the same passage, viz. the levitical priesthood, and the priesthood of Christ. Therefore the Divine law is twofold, namely the Old Law and the New Law.
I answer that, As stated in the First Part (Q. 30, A. 3), distinction is the cause of number. Now things may be distinguished in two ways. First, as those things that are altogether specifically different, e.g. a horse and an ox. Secondly, as perfect and imperfect in the same species, e.g. a boy and a man: and in this way the Divine law is divided into Old and New. Hence the Apostle (Gal. 3:24, 25) compares the state of man under the Old Law to that of a child "under a pedagogue"; but the state under the New Law, to that of a full grown man, who is "no longer under a pedagogue."
Now the perfection and imperfection of these two laws is to be taken in connection with the three conditions pertaining to law, as stated above. For, in the first place, it belongs to law to be directed to the common good as to its end, as stated above (Q. 90, A. 2). This good may be twofold. It may be a sensible and earthly good; and to this, man was directly ordained by the Old Law: wherefore, at the very outset of the law, the people were invited to the earthly kingdom of the Chananaeans (Ex. 3:8, 17). Again it may be an intelligible and heavenly good: and to this, man is ordained by the New Law. Wherefore, at the very beginning of His preaching, Christ invited men to the kingdom of heaven, saying (Matt. 4:17): "Do penance, for the kingdom of heaven is at hand." Hence Augustine says (Contra Faust. iv) that "promises of temporal goods are contained in the Old Testament, for which reason it is called old; but the promise of eternal life belongs to the New Testament."