1. The new law does more than just specify the old. Central to the new law is the gift of the Holy Spirit. By this gift the Christian is nurtured to maturity in Jesus—that is, to everlasting life. Thus, unlike the old law or any other law for fallen men and women, the new law not only indicates the right way—that of Jesus—but empowers one to follow it and draws one along it (see S.t., 1–2, q. 98, a. 1; q. 107, a. 2). It is no mere extrinsic word of exhortation, guidance, challenge, and condemnation; placed in the mind, written in the heart, it is effective in overcoming sin and uniting God’s people with him (see Jer 31.31–34; Heb 8.7–10; 10.15–18).
2. The Old Testament anticipates this. The prophets looked to the time when God would give a new law written in the heart (see Jer 24.7; Bar 2.30–35; Ez 11.19–20; 18.31). The psalmist prayed that God would bring about a change in heart (see Ps 51.12; 119.32). The renewal was to be accomplished by an outpouring of the Spirit of God (see Is 32.15; Ez 39.29).
3. Jesus announces that the Father will give the Spirit to those who ask (see Lk 11.13). At the Last Supper, he promises to send the Holy Spirit (see Jn 14.16–17, 26; 16.7–14). The Spirit will complete Jesus’ work, for he will remain permanently with Christians, lead them to the fullness of Jesus’ truth, and bring the struggle against evil to a victorious conclusion. The promise of the Spirit is fulfilled at Pentecost (see Acts 2.1–4); thus the hope of the prophets is vindicated (see Acts 2.16–21).
4. The law of the Spirit frees Christians from sin and death (see Rom 8.2), for the Spirit dwells in Christians, pours God’s love into their hearts (see Rom 5.5), and makes them God’s children (see Rom 8.14–17). In other words, what is most central in the new law is not a commandment to love or a requirement to do works of fraternal charity, but the actual gift and endowment by the Spirit of the reality and effective power of divine love, which one accepts in living faith (see S.t., 1–2, q. 106, a. 1). This is why the new law is expressed not so much outwardly as in the inner transformation of those who receive it (see 2 Cor 3.2–8).
St. Paul no sooner explains that Christians are liberated from slavery to the yoke of the law than he warns that the freedom of the children of God to which Christians are called is not freedom to do as one pleases. It is a freedom from sin and a power to do the works of love (see Gal 5). This warning of Paul’s still is necessary today and it is so important that further explanation is useful.
In every law except the new law of Jesus, there are two aspects which must be distinguished. On the one hand, to the extent that it truly is law and not merely arbitrary imposition of an exploiting human authority, a law indicates what is necessary or appropriate for action to contribute to human fulfillment. In other words, every true law is a norm which shapes the actions of individuals and groups toward the good to be realized by and shared in through these actions (see S.t., 1–2, q. 90, aa. 1–2; q. 91, a. 4). On the other hand, except for the new law of love, fallen humankind experiences even true law as a more or less unwelcome demand. One who has done wrong perceives the law as the source of reproach to conscience, usually the reproach of society. One who is tempted perceives the law as a curb on inclination. Even one who wants to do what is right perceives the law as a standard difficult to live up to.
When most people think about law, this second aspect—its burdensomeness—is foremost in their minds. Moreover, exploiting human authorities also call their impositions “laws.” The arbitrary demands of unjust authorities, such as Nazi decrees, unjust Supreme Court decisions, and so on are put forth with the trappings of legality. As a result, law is perceived as even more burdensome than it truly is.
5. Any law short of the new law of transforming love seems alien to fallen humankind, the imposition of a burden which cannot be fulfilled (see S.t., 1–2, q. 106, a. 2; q. 107, a. 1, ad 2). This is true even of natural law, for, although it is written in the heart, its dynamism toward human fulfillment is at odds with the stunted dispositions of fallen persons and with the compromises of conventional morality (see S.t., 1–2, q. 94, a. 6; q. 107, a. 4).
6. Christians, however, undergo a real transformation: from the fallen condition to the condition of the new humanity of Jesus. In them, the natural law written in the human heart by the creator and the law of love poured forth in the heart of the redeemed by the Holy Spirit form a harmonious principle of living. This principle is the law of Jesus (see Gal 6.2). The natural law continues to indicate what is necessary and appropriate for human action to contribute to human fulfillment, which will be included in the fulfillment of everything in Jesus. But its indications are now clearer, insofar as a heart renewed by love is freed from the self-deception and rationalization generated to protect the sinful self. And now, too, the love of God provides its impetus toward divine goodness, to be enjoyed by the blessed sharing in it both divinely and humanly.
The law of the Spirit, the new law of love, does not nullify or replace natural law, although the new law does redeem natural law from its aspect of alien imposition (see S.t., 1–2, q. 100, a. 1; q. 107, a. 2, ad 1; q. 108, a. 3, ad 3). As long as the human heart is alienated from itself by sin, even the law written in the heart must be experienced as an alien imposition. When the gift of the Spirit creates a new heart in men and women, the law written by God from the beginning upon the human heart begins to be experienced as the inclination of the real self.
7. The natural law disposes toward friendship with God as one form of humanly fulfilling harmony; living faith superabundantly satisfies this natural disposition (see S.t., 2–2, q. 44, a. 1). At the same time, the new law of love disposes one toward a human life in perfect harmony with God’s will; thus it disposes one to the perfect carrying-out of the natural law, since God wills integral fulfillment for his human children.
8. The disposition to fulfillment in Jesus comprehends and exceeds the human requirement to choose consistently with integral human fulfillment. Hence, love fulfills all the commandments (see Rom 13.8–10; 1 Cor 13; Gal 5.14–23).
9. Insofar as Christians are true to their calling, they are altogether freed from law in its burdensome, alien aspect.13 The share in divine love communicated to them by the Spirit is a disposition to divine goodness and so to everything good, for every good comes from God, participates in his perfection, and contributes to the fulfillment of all things in Jesus. To hearts formed by divine love nothing that is good is alien (see Phil 4.8–9), and right ways of acting—that is, ways to the good—are spontaneously preferred. Thus St. Paul stresses that the Christian is liberated from the law: One who lives by the Spirit spontaneously does what is conducive to good; law’s demands are satisfied without being made (see S.t., 1–2, q. 106, aa. 1–2).
13. Emphasis on this truth, combined with a fundamentally sound understanding of the specificity of Christian ethics, tends to cloud the issue concerning specific norms. See, for example, Yves Congar, O.P., “Réflexion et Propos sur l’Originalité d’Une Ethique Chrétienne,” in In Libertatem Vocati Estis, ed. H. Boelaars and R. Tremblay (Rome: Academia Alfonsiana, 1977), 31–40. However, truth of a practical order remains when it is spontaneously fulfilled, and can be articulated with precision (see 26‑D–K).