Secondly, it belongs to the law to direct human acts according to the order of righteousness (A. 4): wherein also the New Law surpasses the Old Law, since it directs our internal acts, according to Matt. 5:20: "Unless your justice abound more than that of the Scribes and Pharisees, you shall not enter into the kingdom of heaven." Hence the saying that "the Old Law restrains the hand, but the New Law controls the mind" ( Sentent. iii, D, xl).
Thirdly, it belongs to the law to induce men to observe its commandments. This the Old Law did by the fear of punishment: but the New Law, by love, which is poured into our hearts by the grace of Christ, bestowed in the New Law, but foreshadowed in the Old. Hence Augustine says (Contra Adimant. Manich. discip. xvii) that "there is little difference [*The 'little difference' refers to the Latin words 'timor' and 'amor'—'fear' and 'love.'] between the Law and the Gospel—fear and love."
Reply Obj. 1: As the father of a family issues different commands to the children and to the adults, so also the one King, God, in His one kingdom, gave one law to men, while they were yet imperfect, and another more perfect law, when, by the preceding law, they had been led to a greater capacity for Divine things.
Reply Obj. 2: The salvation of man could not be achieved otherwise than through Christ, according to Acts 4:12: "There is no other name . . . given to men, whereby we must be saved." Consequently the law that brings all to salvation could not be given until after the coming of Christ. But before His coming it was necessary to give to the people, of whom Christ was to be born, a law containing certain rudiments of righteousness unto salvation, in order to prepare them to receive Him.
Reply Obj. 3: The natural law directs man by way of certain general precepts, common to both the perfect and the imperfect: wherefore it is one and the same for all. But the Divine law directs man also in certain particular matters, to which the perfect and imperfect do not stand in the same relation. Hence the necessity for the Divine law to be twofold, as already explained. ________________________
SIXTH ARTICLE [I-II, Q. 91, Art. 6]
Whether There Is a Law in the Fomes of Sin?
Objection 1: It would seem that there is no law of the fomes of
sin. For Isidore says (Etym. v) that the "law is based on reason."
But the fomes of sin is not based on reason, but deviates from it.
Therefore the fomes has not the nature of a law.
Obj. 2: Further, every law is binding, so that those who do not obey it are called transgressors. But man is not called a transgressor, from not following the instigations of the fomes; but rather from his following them. Therefore the fomes has not the nature of a law.
Obj. 3: Further, the law is ordained to the common good, as stated above (Q. 90, A. 2). But the fomes inclines us, not to the common, but to our own private good. Therefore the fomes has not the nature of sin.