Nevertheless the New Law contains certain things that dispose us to receive the grace of the Holy Ghost, and pertaining to the use of that grace: such things are of secondary importance, so to speak, in the New Law; and the faithful need to be instructed concerning them, both by word and writing, both as to what they should believe and as to what they should do. Consequently we must say that the New Law is in the first place a law that is inscribed on our hearts, but that secondarily it is a written law.
Reply Obj. 1: The Gospel writings contain only such things as pertain to the grace of the Holy Ghost, either by disposing us thereto, or by directing us to the use thereof. Thus with regard to the intellect, the Gospel contains certain matters pertaining to the manifestation of Christ's Godhead or humanity, which dispose us by means of faith through which we receive the grace of the Holy Ghost: and with regard to the affections, it contains matters touching the contempt of the world, whereby man is rendered fit to receive the grace of the Holy Ghost: for "the world," i.e. worldly men, "cannot receive" the Holy Ghost (John 14:17). As to the use of spiritual grace, this consists in works of virtue to which the writings of the New Testament exhort men in divers ways.
Reply Obj. 2: There are two ways in which a thing may be instilled into man. First, through being part of his nature, and thus the natural law is instilled into man. Secondly, a thing is instilled into man by being, as it were, added on to his nature by a gift of grace. In this way the New Law is instilled into man, not only by indicating to him what he should do, but also by helping him to accomplish it.
Reply Obj. 3: No man ever had the grace of the Holy Ghost except through faith in Christ either explicit or implicit: and by faith in Christ man belongs to the New Testament. Consequently whoever had the law of grace instilled into them belonged to the New Testament. ________________________
SECOND ARTICLE [I-II, Q. 106, Art. 2]
Whether the New Law Justifies?
Objection 1: It would seem that the New Law does not justify. For no man is justified unless he obeys God's law, according to Heb. 5:9: "He," i.e. Christ, "became to all that obey Him the cause of eternal salvation." But the Gospel does not always cause men to believe in it: for it is written (Rom. 10:16): "All do not obey the Gospel." Therefore the New Law does not justify.
Obj. 2: Further, the Apostle proves in his epistle to the Romans that the Old Law did not justify, because transgression increased at its advent: for it is stated (Rom. 4:15): "The Law worketh wrath: for where there is no law, neither is there transgression." But much more did the New Law increase transgression: since he who sins after the giving of the New Law deserves greater punishment, according to Heb. 10:28, 29: "A man making void the Law of Moses dieth without any mercy under two or three witnesses. How much more, do you think, he deserveth worse punishments, who hath trodden underfoot the Son of God," etc.? Therefore the New Law, like the Old Law, does not justify.
Obj. 3: Further, justification is an effect proper to God, according to Rom. 8:33: "God that justifieth." But the Old Law was from God just as the New Law. Therefore the New Law does not justify any more than the Old Law.
On the contrary, The Apostle says (Rom. 1:16): "I am not ashamed of the Gospel: for it is the power of God unto salvation to everyone that believeth." But there is no salvation but to those who are justified. Therefore the Law of the Gospel justifies.