In this matter Vatican I adopts the position of St. Thomas (S.t.,1, q. 1, a. 1; 1–2, q. 98, a. 5; S.c.g., 1, 4). Thomas expands on the general position with respect to the particular question: Can the natural law be wiped from the human heart? His answer is that the most common principles in themselves cannot be ignored, but their application in the concrete can be ignored due to unruly passions; and norms which must be derived from the most general principles by any sort of reasoning can be ignored due to bad customs and corrupt habits (S.t., 1–2, q. 93, a. 6; cf. q. 77, a. 2; q. 85, a. 3).

Pius XII refers to Vatican I and expands upon it, in line with the teaching of St. Thomas:

. . . though, absolutely speaking, human reason by its own natural force and light can arrive at a true and certain knowledge of the one personal God, Who by His providence watches over and governs the world, and also the natural law, which the Creator has written in our hearts, still there are not a few obstacles to prevent reason from making efficient and fruitful use of its natural ability.  . . .
  It is for this reason that divine revelation must be considered morally necessary so that those religious and moral truths which are not of their nature beyond the reach of reason in the present condition of the human race, may be known with a firm certainty and with freedom from all error.⁶

2. Thus the Church teaches that revelation includes truths of natural law.⁸ This provides a premise for rejecting certain conclusions which today are often drawn—mistakenly—from the fact that natural law is naturally knowable. For instance, some theologians claim that the Church cannot authoritatively teach specific moral norms pertaining to natural law, but can only endorse norms agreed upon by people of good will, Christians and others.⁹ Indeed, some theologians hold that the authority of any specific moral norm received and handed on in the Church can be no greater than the rational arguments which can be offered to support it.¹⁰ Thus they conclude that while the Church can firmly teach the very general principles of morality with which no believer disagrees and may tentatively commend specific norms supported by consensus and rational arguments, the Church cannot authoritatively teach specific moral norms pertaining to natural law in such a way that the faithful ought to accept them as moral truths even if consensus and cogent rational arguments are lacking.¹¹

3. The teaching of Vatican I concerning the help given to fallen humankind by revelation explains why many people of good will do not see the truth of moral norms of natural law. The Church’s teaching, based on divine revelation, gives us a motive to accept as true those norms of Christian morality for which we may not have completely satisfying arguments. Moreover, as part of her divine mission the Church calls attention by her sacred and certain teaching to the principles of the moral order, which we can ignore or badly articulate despite knowing them naturally (see DH 14; GS 89). (The issues concerning theological dissent from the Church’s moral teaching will be examined in chapter thirty-six.)

4. The argument that revelation contains no specific moral norms but only very general principles is at odds with the entire history of Christian moral teaching. Christians always have handed on specific norms as revealed truths and offered scriptural warrants for them.¹² For example, the Council of Trent cites St. Paul to show that several kinds of acts other than sins against faith itself are mortal sins (see DS 1544/808). Similarly, Vatican II proposes specific norms concerning forgiving injuries and loving enemies as the teaching of Christ, citing Matthew’s account of the Sermon on the Mount (see GS 28).

5. Moreover, both Trent and Vatican II teach that the gospel which Jesus proclaimed and commissioned the apostles to spread is the “source of all saving truth and moral teaching” (DS 1501/783; DV 7; note that the “omnis” comes before the first “et”).¹³ How the gospel contains all moral teaching will be made clear in chapter twenty-six. The key point is that God reveals in Jesus how men and women in a sinful world should respond to his love and live good human lives which necessarily will be redemptive like the life of Jesus himself.

6. Thus Vatican II teaches that Christ “fully reveals man to man himself and makes his supreme calling clear” (GS 22). “Whoever follows after Christ, the perfect man, becomes himself more of a man” (GS 41). By Christian holiness, “a more human way of life is promoted even in this earthly society” (LG 40).

7. Vatican II’s understanding of the relationship between divine and natural law is exemplified in its teaching on birth regulation. According to the Council, the Church authoritatively interprets divine law in the light of the gospel to make clear objective standards based on the nature of human persons and their acts (see GS 50–51). Again, the Council teaches that the Church contributes to international peace and friendship by imparting knowledge of divine and natural law, and that this work belongs to the Church’s divine mission of preaching the gospel and dispensing the treasures of grace (see GS 89, Latin text). This teaching would be unintelligible if, as some wish, divine law and natural law were separated, with the Church’s teaching authority limited to the former while all specific moral issues were consigned to independent rational reflection on experience.¹⁴

8. It follows that natural law and divine law can be distinguished from each other and even contrasted, as they are in many documents of the Church, without being separated and opposed to each other.¹⁵ In the actual order of things natural law does not stand apart from the law of Christ. The dictates of natural law and the truth of divine revelation are two agreeing streams from the same divine font; the Church is the guardian of the single supernatural Christian order, in which nature and grace converge.¹⁶ In this Christian order, natural law is restored, completed, and elevated, so that it now serves to direct humankind to heavenly as well as earthly fulfillment.¹⁷ A real Christian life is a humanly good life—the only completely fulfilling life for persons who, called to share in divine life, have fallen and been redeemed.

. . . even if (per impossibile, I should think) the natural law was not integral to the gospel, the Church’s prerogative to propose infallibly the gospel morality would be no more than nugatory without the power to teach the natural law infallibly. One could hardly propose what concerns Christian men without proposing what concerns men. The Church could hardly propose Christian love in any meaningful way without being able to propose the very suppositions of any love. In other words, and from this point of view alone, to propose the natural law is essential to the protection and proposal of Christian morality itself, much as certain philosophical truths are capable of definition because without them revealed truths are endangered. Furthermore, charity has no external act of its own. It can express itself only through acts of other virtues. But natural-law demands constitute the most basic demands of these virtues, simply because we can never escape the fact that it is man who is loving and to be loved. Would not, therefore, the ability to teach infallibly the dignity of man (certainly a revealed truth) without being able to exclude infallibly forms of conduct incompatible with this dignity be the ability infallibly to propose a cliche?¹⁸

6. Pius XII, Humani generis, 42 AAS (1950) 561–62; The Papal Encyclicals, 240.2–3. See also Pius XI, Casti connubii, 22 AAS (1930) 579–80; The Papal Encyclicals, 208.102–3, for a development of the same point, and the foundation of the competency of the Church in marriage morality in God’s supplementation of the light of reason by revelation, whose interpretation is entrusted to the Church’s teaching office.

7. S.t., 1–2, q. 100, aa. 1 and 3; St. Irenaeus, Adversus Haereses, iv, 13, 1 and 4. See Dario Composta, “Il diritto naturale in S. Ireneo,” Apollinaris, 45 (1972), 599–612. See the brief, cogent exegetical study of the fathers: Guy Bourgeault, “La spécificité de la morale chrétienne selon les Pères des deux premiers siècles,” Science et Esprit, 23 (1971), 137–52. Classical Lutheran ethics did not take a different point of view on this matter: Theodore R. Jungkuntz, “Trinitarian Ethics,” Center Journal, 1 (Spring 1982), 48–51.

8. Sound exegetical studies confirm the truth of the Church’s teaching with respect to Scripture. See, for example, the brilliant summary by a leading, non-Catholic Scripture scholar: W. D. Davies, “Ethics in the New Testament,” Interpreter’s Dictionary of the Bible, 2:167–76. In the Old Testament, too, God’s law is presented as an expression of wisdom recognizable in principle as valid by the nations (see Dt 4.5–8); for a helpful analysis: Jon D. Levenson, “The Theologies of Commandment in Biblical Israel,” Harvard Theological Review, 73 (1980), 17–33.

9. See summaries in Richard A. McCormick, S.J., Notes on Moral Theology: 1965 through 1980 (Washington, D.C.: University Press of America, 1981), 251–58 and 684–87 (hereinafter cited as “Notes”). Also: Timothy E. O’Connell, Principles for a Catholic Morality (New York: Seabury Press, 1978), 96–97.

10. Besides the materials cited in the preceding note, see Richard A. McCormick, S.J., “Moral Theology since Vatican II: Clarity or Chaos,” Cross Currents, 29 (Spring 1979), 25; he says that a fresh notion of the magisterium has emerged and within its perspective “much more attention is given to evidence and analyses in evaluating authentic teaching. Only persuasive arguments command assent.” Gerard J. Hughes, S.J., Authority in Morals: An Essay in Christian Ethics (London: Heythrop Monographs, 1978), denies that “appeal to revelation will enable us to solve moral dilemmas to which there is no other adequate solution” (10). He holds “that there is no specifically Christian authority in ethics by appeal to which we can effectively hope to foreclose any moral argument,” and that any moral authority “owes its status as an authority to the success with which it interprets the facts, and it is to these alone that any ultimate appeal can be made” (123–24).

11. The position is sometimes put in terms of an injunction that the magisterium’s role is to ask questions on moral issues rather than to answer them, or to conduct a dialogue to elicit the insights of the faithful: Charles E. Curran, Themes in Fundamental Moral Theology (Notre Dame and London: University of Notre Dame Press, 1977), 118: “Too often in the past the teaching or prophetic role of the Church has been seen in giving answers or pronouncements to particular questions. This approach wedded to a claim of absolute certitude actually hindered the Church from properly fulfilling its teaching and prophetic function.” Cf. Bernard Häring, Free and Faithful in Christ: Moral Theology for Clergy and Laity, vol. 1, General Moral Theology (New York: Seabury Press, 1978), 331–33.

12. For example, the story about Onan (see Gn 38.9–10) was very often cited as the basis of the Church’s teaching on contraception. No matter what anyone today thinks this passage means, the fact that it was used as it was shows that those who handed on the teaching believed it was divinely revealed—see, e.g., Casti connubii, quoting St. Augustine, 22 AAS (1930) 559–60; The Papal Encyclicals, 208.55. In a symposium conducted after the publication of Humanae vitae, Joseph Coppens, an Old Testament scholar, made this precise point: “All moral textbooks, theological and philosophical, from the earliest centuries on, speak of Onan’s sin as contraception. (Whether this agrees with contemporary scholarship, which sees Onan’s sin as a refusal to obey the levirate law, is not at issue here.) Onan’s sin has been constantly and universally condemned; this is the constant teaching referred to in the encyclical” (“A Symposium on ‘Humanae vitae’ and the Natural Law,” Louvain Studies, 2 [Spring 1969], 224).

13. It has been argued that the phrase, “faith and morals,” has shifted its meaning in the course of history: Piet Fransen, S.J., “A Short History of the Meaning of the Formula, ‘Fides et Mores,’ ” Louvain Studies, 7 (1979), 270–301. Up to Trent, “morals” denoted (Always? Or, perhaps, only sometimes?) legal institutions we would not include in that category today. But it is not shown that Christian moral norms ever have been outside the reference of one or the other term, for since Trent “morals” came to refer to them, while in earlier times “faith” was less limited (to assent to propositional truths) and had a more inclusive, existential sense. Prior to the Reformation, all Christians believed that saving faith included both assent to the truths of faith and a real effort to live up to them. See Teodoro López Rodriguez, “ ‘Fides et mores’ en Trento,” Scripta Theologica, 5 (1973), 175–221; Marcelino Zalba, S.J., “ ‘Omnis et salutaris veritas et morum disciplina’: Sentido de la expresión ‘mores’ en el Concilio de Trento,” Gregorianum, 54 (1973), 679–715.

14. The continuity between the papal magisterium and Vatican II on the Church’s competency in teaching natural law is shown by John J. Reed, S.J., “Natural Law, Theology, and the Church,” Theological Studies, 26 (1965), 40–64. See also the helpful discussion by McCormick (at the time in agreement with Reed and critical of Gregory Baum’s views: Notes, 16–20. For a commentary on Vatican II’s teaching on natural law with a critique of some current theological positions at odds with it, see John Finnis, “The Natural Law, Objective Morality, and Vatican II,” in Principles of Catholic Moral Life, ed. William E. May (Chicago: Franciscan Herald Press, 1980), 113–49. A critique of views which attempt to separate autonomous morality from faith: Ferdinando Citterio, “Morale autonoma e fede cristiana: Il dibattito continua,” Scuola cattolica, 108 (1980), 509–61, esp. 542–6l; 109 (1981), 3–29, esp. 26–29.

15. See Josef Fuchs, S.J., Natural Law: A Theological Investigation (New York: Sheed and Ward, 1965), 10. This book, written before Fuchs became a proportionalist, is reliable in general, although it is imbued with scholastic natural-law theory. See also Edouard Hamel, S.J., Loi Naturelle et Loi du Christ (Bruges: Desclée de Brouwer, 1964), 11–43.

16. Pius XII, “Nuntius Radiophonicus” (1 June 1941), 33 AAS (1941) 197; see Fuchs, op. cit., 12. In his inaugural encyclical, Summi Pontificatus, 31 AAS (1939) 423–25; The Papal Encyclicals, 222.28–32, Pius XII, writing at the outbreak of World War II, traces the descending darkness back to the Reformation, with its “abandonment of that Christian teaching of which the Chair of Peter is the depository and exponent.” “Cut off from the infallible teaching authority of the Church, not a few separated brethren have gone so far as to overthrow the central dogma of Christianity, the Divinity of the Saviour, and have hastened thereby the progress of spiritual decay.” Secularization—the emergence of a new paganism—resulted in the stilling or weakening of conscience, due to “the inability of all human effort to replace the law of Christ by anything equal to it.” Thus the cause of the deplorable evils of modern society “is the denial and rejection of a universal norm of morality as well for individual and social life as for international relations; We mean the disregard, so common nowadays, and the forgetfulness of the natural law itself, which has its foundation in God.” In sum: “With the weakening of faith in God and in Jesus Christ, and the darkening in men’s minds of the light of moral principles, there disappeared the indispensable foundation of the stability and quiet of that internal and external, private and public order, which alone can support and safeguard the prosperity of States.”

17. See Leo XIII, Tametsi futura prospicientibus, 33 ASS (1900–1901) 279; The Papal Encyclicals, 153.7; “By the law of Christ we mean not only the natural precepts of morality and the Ancient Law, all of which Jesus Christ has perfected and crowned by His declaration, explanation and sanction; but also the rest of His doctrine and His own peculiar institutions.” See also Pius IX, Qui pluribus, Pii IX Acta (1846–54), I, 1:10; The Papal Encyclicals, 40.10: “God Himself has set up a living authority to establish and teach the true and legitimate meaning of His heavenly revelation. This authority judges infallibly all disputes which concern matters of faith and morals, lest the faithful be swirled around by every wind of doctrine which springs from the evilness of men in encompassing error.” Pius XI, Mit brennender Sorge, 29 AAS (1937) 158–59; The Papal Encyclicals, 218.29: “It is on faith in God, preserved pure and stainless, that man’s morality is based.” Pius XII, Ad Apostolorum Principis, 50 AAS (1958) 608; The Papal Encyclicals, 261.33: “By God’s appointment the observance of the natural law concerns the way by which man must strive toward his supernatural end. The Church shows the way and is the guide and guardian of men with respect to their supernatural end.” Among the theologians who explain and defend this position: Carlo Caffarra, Viventi in Cristo (Milan: Jaca Book, 1981); Ermenegildo Lio, Morale e beni terreni: La destinazione universale dei beni terreni nella “Gaudium et spes” (Rome: Città Nuova, 1976), 18–29; Jean-Marie Aubert, “La morale chrétienne selon saint Thomas,” Seminarium, 29 (1977), 780–811.

18. McCormick, Notes, 20.