1950 The moral law is the work of divine Wisdom. Its biblical meaning can be defined as fatherly instruction, God's pedagogy. It prescribes for man the ways, the rules of conduct that lead to the promised beatitude; it proscribes the ways of evil which turn him away from God and his love. It is at once firm in its precepts and, in its promises, worthy of love.
1951 Law is a rule of conduct enacted by competent authority for the sake of the common good. The moral law presupposes the rational order, established among creatures for their good and to serve their final end, by the power, wisdom, and goodness of the Creator. All law finds its first and ultimate truth in the eternal law. Law is declared and established by reason as a participation in the providence of the living God, Creator and Redeemer of all. "Such an ordinance of reason is what one calls law."2
1952 There are different expressions of the moral law, all of them interrelated: eternal law - the source, in God, of all law; natural law; revealed law, comprising the Old Law and the New Law, or Law of the Gospel; finally, civil and ecclesiastical laws.
1953 The moral law finds its fullness and its unity in Christ. Jesus Christ is in person the way of perfection. He is the end of the law, for only he teaches and bestows the justice of God: "For Christ is the end of the law, that every one who has faith may be justified."4
1954 Man participates in the wisdom and goodness of the Creator who gives him mastery over his acts and the ability to govern himself with a view to the true and the good. The natural law expresses the original moral sense which enables man to discern by reason the good and the evil, the truth and the lie:
1955 The "divine and natural" law6 shows man the way to follow so as to practice the good and attain his end. The natural law states the first and essential precepts which govern the moral life. It hinges upon the desire for God and submission to him, who is the source and judge of all that is good, as well as upon the sense that the other is one's equal. Its principal precepts are expressed in the Decalogue. This law is called "natural," not in reference to the nature of irrational beings, but because reason which decrees it properly belongs to human nature:
1956 The natural law, present in the heart of each man and established by reason, is universal in its precepts and its authority extends to all men. It expresses the dignity of the person and determines the basis for his fundamental rights and duties:
1957 Application of the natural law varies greatly; it can demand reflection that takes account of various conditions of life according to places, times, and circumstances. Nevertheless, in the diversity of cultures, the natural law remains as a rule that binds men among themselves and imposes on them, beyond the inevitable differences, common principles.
1958 The natural law is immutable and permanent throughout the variations of history;10 it subsists under the flux of ideas and customs and supports their progress. The rules that express it remain substantially valid. Even when it is rejected in its very principles, it cannot be destroyed or removed from the heart of man. It always rises again in the life of individuals and societies:
1959 The natural law, the Creator's very good work, provides the solid foundation on which man can build the structure of moral rules to guide his choices. It also provides the indispensable moral foundation for building the human community. Finally, it provides the necessary basis for the civil law with which it is connected, whether by a reflection that draws conclusions from its principles, or by additions of a positive and juridical nature.
1960 The precepts of natural law are not perceived by everyone clearly and immediately. In the present situation sinful man needs grace and revelation so moral and religious truths may be known "by everyone with facility, with firm certainty and with no admixture of error."12 The natural law provides revealed law and grace with a foundation prepared by God and in accordance with the work of the Spirit.
1961 God, our Creator and Redeemer, chose Israel for himself to be his people and revealed his Law to them, thus preparing for the coming of Christ. The Law of Moses expresses many truths naturally accessible to reason. These are stated and authenticated within the covenant of salvation.
1962 The Old Law is the first stage of revealed Law. Its moral prescriptions are summed up in the Ten Commandments. The precepts of the Decalogue lay the foundations for the vocation of man fashioned in the image of God; they prohibit what is contrary to the love of God and neighbor and prescribe what is essential to it. The Decalogue is a light offered to the conscience of every man to make God's call and ways known to him and to protect him against evil:
1963 According to Christian tradition, the Law is holy, spiritual, and good,14 yet still imperfect. Like a tutor15 it shows what must be done, but does not of itself give the strength, the grace of the Spirit, to fulfill it. Because of sin, which it cannot remove, it remains a law of bondage. According to St. Paul, its special function is to denounce and disclose sin, which constitutes a "law of concupiscence" in the human heart.16 However, the Law remains the first stage on the way to the kingdom. It prepares and disposes the chosen people and each Christian for conversion and faith in the Savior God. It provides a teaching which endures for ever, like the Word of God.
1964 The Old Law is a preparation for the Gospel. "The Law is a pedagogy and a prophecy of things to come."17 It prophesies and presages the work of liberation from sin which will be fulfilled in Christ: it provides the New Testament with images, "types," and symbols for expressing the life according to the Spirit. Finally, the Law is completed by the teaching of the sapiential books and the prophets which set its course toward the New Covenant and the Kingdom of heaven.
1965 The New Law or the Law of the Gospel is the perfection here on earth of the divine law, natural and revealed. It is the work of Christ and is expressed particularly in the Sermon on the Mount. It is also the work of the Holy Spirit and through him it becomes the interior law of charity: "I will establish a New Covenant with the house of Israel. . . . I will put my laws into their hands, and write them on their hearts, and I will be their God, and they shall be my people."19
1966 The New Law is the grace of the Holy Spirit given to the faithful through faith in Christ. It works through charity; it uses the Sermon on the Mount to teach us what must be done and makes use of the sacraments to give us the grace to do it:
1967 The Law of the Gospel "fulfills," refines, surpasses, and leads the Old Law to its perfection.21 In the Beatitudes, the New Law fulfills the divine promises by elevating and orienting them toward the "kingdom of heaven." It is addressed to those open to accepting this new hope with faith - the poor, the humble, the afflicted, the pure of heart, those persecuted on account of Christ and so marks out the surprising ways of the Kingdom.
1968 The Law of the Gospel fulfills the commandments of the Law. The Lord's Sermon on the Mount, far from abolishing or devaluing the moral prescriptions of the Old Law, releases their hidden potential and has new demands arise from them: it reveals their entire divine and human truth. It does not add new external precepts, but proceeds to reform the heart, the root of human acts, where man chooses between the pure and the impure,22 where faith, hope, and charity are formed and with them the other virtues. The Gospel thus brings the Law to its fullness through imitation of the perfection of the heavenly Father, through forgiveness of enemies and prayer for persecutors, in emulation of the divine generosity.23
1969 The New Law practices the acts of religion: almsgiving, prayer and fasting, directing them to the "Father who sees in secret," in contrast with the desire to "be seen by men."24 Its prayer is the Our Father.25
1970 The Law of the Gospel requires us to make the decisive choice between "the two ways" and to put into practice the words of the Lord.26 It is summed up in the Golden Rule, "Whatever you wish that men would do to you, do so to them; this is the law and the prophets."27
The entire Law of the Gospel is contained in the "new commandment" of Jesus, to love one another as he has loved us.28
1971 To the Lord's Sermon on the Mount it is fitting to add the moral catechesis of the apostolic teachings, such as Romans 12-15, 1 Corinthians 12-13, Colossians 3-4, Ephesians 4-5, etc. This doctrine hands on the Lord's teaching with the authority of the apostles, particularly in the presentation of the virtues that flow from faith in Christ and are animated by charity, the principal gift of the Holy Spirit. "Let charity be genuine. . . . Love one another with brotherly affection. . . . Rejoice in your hope, be patient in tribulation, be constant in prayer. Contribute to the needs of the saints, practice hospitality."29 This catechesis also teaches us to deal with cases of conscience in the light of our relationship to Christ and to the Church.30
1972 The New Law is called a law of love because it makes us act out of the love infused by the Holy Spirit, rather than from fear; a law of grace, because it confers the strength of grace to act, by means of faith and the sacraments; a law of freedom, because it sets us free from the ritual and juridical observances of the Old Law, inclines us to act spontaneously by the prompting of charity and, finally, lets us pass from the condition of a servant who "does not know what his master is doing" to that of a friend of Christ - "For all that I have heard from my Father I have made known to you" - or even to the status of son and heir.31
1973 Besides its precepts, the New Law also includes the evangelical counsels. The traditional distinction between God's commandments and the evangelical counsels is drawn in relation to charity, the perfection of Christian life. The precepts are intended to remove whatever is incompatible with charity. The aim of the counsels is to remove whatever might hinder the development of charity, even if it is not contrary to it.32
1974 The evangelical counsels manifest the living fullness of charity, which is never satisfied with not giving more. They attest its vitality and call forth our spiritual readiness. The perfection of the New Law consists essentially in the precepts of love of God and neighbor. The counsels point out the more direct ways, the readier means, and are to be practiced in keeping with the vocation of each:
1978 The natural law is a participation in God's wisdom and goodness by man formed in the image of his Creator. It expresses the dignity of the human person and forms the basis of his fundamental rights and duties.
1983 The New Law is the grace of the Holy Spirit received by faith in Christ, operating through charity. It finds expression above all in the Lord's Sermon on the Mount and uses the sacraments to communicate grace to us.
1984 The Law of the Gospel fulfills and surpasses the Old Law and brings it to perfection: its promises, through the Beatitudes of the Kingdom of heaven; its commandments, by reforming the heart, the root of human acts.
1986 Besides its precepts the New Law includes the evangelical counsels. "The Church's holiness is fostered in a special way by the manifold counsels which the Lord proposes to his disciples in the Gospel" (LG 42 § 2).
2 Leo XIII, Libertas præstantissimum: AAS 20 (1887/88),597; cf. St. Thomas Aquinas, STh I-II,90,1.