347. Comparison of the Two Testaments from Other Viewpoints.—(a) The aim of both Laws is to secure obedience to God and holiness for man. But the New Testament, since given to those who were better prepared and more perfect, unveils more clearly the mysteries of faith, enjoins more perfect works, and supplements the Commandments with counsels of perfection (cfr. the Sermon on the Mount).
(b) Both Laws make use of threats, promises and persuasion in order to move men to obedience. But, as the Old Law was for those who were spiritually but children, it dwells especially on the punishments to be meted out to transgressors and the external rewards that will be given to the obedient (the law of fear); whereas the New Law, being for those who are spiritually mature, holds out as inducements chiefly the love of virtue and rewards that are internal and spiritual (the law of love).
(c) The author of both laws is God. But, while the Old Law was announced through God’s servants as the preparatory dispensation, the New Law was proclaimed by the Son of God Himself as the final economy of human salvation: “God, who at sundry times spoke in times past to the fathers by the prophets, last of all in these days hath spoken to us by His Son, whom He hath appointed heir of all things” (Heb, ii. 1).
348. Differences in the Precepts of the Two Laws.—(a) There is no opposition between the commandments of the two Laws; for the ceremonial and judicial precepts of the Old Law, which contained figure and prophecy, are fulfilled in the precepts of Christ, while the moral laws of the Old Testament are confirmed and perfected by the moral laws of Christ: “I am not come to destroy, but to fulfill” (Matt., v. 17).
(b) There is no substantial difference between the faith and works of the two Testaments. For, that which is now believed explicitly and clearly, was believed implicitly and in figure in the Old Testament, and the greater things that now are commanded were contained germinally in the precepts of the Old Law.
349. The Old and the New Law Compared as to Difficulty.—(a) If we consider the difficulty that arises from the fulfillment of external works, the Old Law was much more difficult. For while the Law of Moses imposed numerous and complicated ceremonies and observances, the Law of Christ commands but few and simple rites. Of the Old Law St. Peter says that it was a yoke, “which neither our fathers nor we have been able to bear” (Acts, xv. 10)—that is, it was extremely burdensome; but of His own Law Christ says: “My yoke is sweet, and My burden light” (Matt, xi. 30). Even the additions made by Christ to the Old Law (e.g., the prohibition against divorce) really facilitate that which the Old Law itself intended—viz., the perfection of man. Hence, the Old Law is the law of servitude; the New Law, the law of liberty.
(b) If we consider the difficulty that arises from internal works, or the dispositions and motives with which precepts are to be fulfilled, the New Law is more difficult; for it inculcates a loftier piety and gives more attention to the spirit with which God is to be worshipped. But, since love is the all-inclusive commandment of Christ, and since gladness and fervor are easy to the lover, the commandments of Christ “are not heavy” (I John, v. 3).
350. The External Works Commended by Christ.—(a) Since the New Law is the law of grace, it commands only those things by which we are brought to grace, or by means of which we make use of grace already received. We receive grace only through Christ, and hence there are commandments regarding the Sacraments; we make right use of grace by faith that worketh through charity, and hence there are the precepts of the Decalogue to be kept.
(b) Since the New Law is the law of liberty, it does not determine the details of the moral law, nor prescribe minutely how we must worship God and observe justice to others, as was done in the ceremonial and judicial laws of the Old Testament. Minor dispositions of this kind have no necessary relation to internal grace, being morally indifferent. Hence, Christ left many things free, to be determined later according to conditions, either by the individual (in personal matters) or by the spiritual or temporal authority (in matters of public concern). It is contrary to the spirit of the Gospel, however, that mankind should be oppressed with numerous and burdensome observances.
351. The Internal Works Commanded by Christ.—In the Sermon on the Mount were given the commandments of the New Law that summarize the entire duty of the Christian as to his internal acts: “Everyone that heareth these My words, and doeth them, shall be likened to a wise man that built his house upon a rock” (Matt., vii. 24). Thus, there are: (a) internal acts commanded as regards our own wills and purposes (we must avoid not only external, but also internal sins and the occasions of sin; we must not only do good, but we must have a good motive, not placing our end in human applause or riches); (b) internal acts commanded as regards our neighbor (we must not judge him rashly, unjustly, presumptuously; nor must we trust him imprudently); (c) interior dispositions with which we must perform our duties (we must avoid inordinate cares, imploring and expecting the divine assistance; but we must also avoid carelessness, having our minds set on the narrow way, and eschewing seductions).