Why Protestants Need Natural Law

On learning from God’s “second book”

“Go to the ant, O sluggard; consider her ways, and be wise. Without having any chief, officer, or ruler, she prepares her bread in summer and gathers her food in harvest.” (Proverbs 6:6-8)[1. Unless otherwise noted, all biblical quotes are from the ESV.]

In Proverbs 6:6-8, Solomon points the reader to the natural order, and invites the reader to observe it, noting the ways in which non-rational beings act in an ordained manner for their own good, both present and future. He then invites the reader to learn how to live from their observations of nature. Our observations can either confirm our actions, if we are diligent in our labors, or condemn us and motivate us if we have become lazy. In this way, and in many other ways, the Christian Scriptures teach, and Christian theologians throughout the history of the church have taught, that there is a natural law. Our purpose, in this essay, is to argue that natural law has been, and should still be, a key doctrine in Protestant theology.[2. So much has been written on the subject that it is impossible, in a short article, to provide a helpful survey of the literature. For those who are interested in a more in-depth engagement with the early Protestant views of natural law, see: Stephen J. Grabill, Rediscovering the Natural Law in Reformed Theological Ethics (Grand Rapids, MI: Wm. B. Eerdmans Co., 2006). There is also some discussion of it in Richard A. Muller, Prolegomena to Theology, vol. 1 of Post-Reformation Reformed Dogmatics, 2nd ed. (Grand Rapids, MI: Baker Academic, 2003).] To do this, we will begin by explaining what is meant by the term “natural law.” We will then take a brief look at the biblical basis for natural law, and conclude with some comments about its relative importance and use in contemporary debates about moral issues.

What is natural law?

Christian theologians have traditionally noted a number of distinctions between different types of law. Considering the types of law in a hierarchical order, beginning with the highest, we note that eternal law is essentially the mind of God in its providential relation to the things he has created—containing the “archetypes” of all created things.[3. Cf. Thomas Aquinas, Summa Theologiae (ST) I-II, q. 93, a. 1, resp. Richard Hooker, The Laws of Ecclesiastical Polity in Modern English (LEP), ed. Bradford Littlejohn, Bradley Belschner, Brian Marr, and Sean Duncan (Lincoln, NB: The Davenant Press, 2019), 50, 53, 54. Girolamo Zanchi, On the Law in General (OLG), trans. Jeffrey J. Veenstra (Grand Rapids, MI: Acton Institute, 2012), 5-7.] Natural law has been described by various authors as that part of eternal law which specifically applies to human beings.[4. Cf. Aquinas, ST I-II, q. 91, a. 2, resp.; q. 94. One might distinguish the laws of nature from the natural law, by saying that the laws of nature are those parts of eternal law which apply to all creatures other than humans and angels. Richard Hooker, for example, defines natural law as that part of the eternal law which applies to creatures, and then uses the term “law of reason” as that part of the natural law which applies to humans—rational animals (cf. Hooker, LEP, 54-55.). That part of eternal law which applies to angels is called, by Hooker, celestial law (Hooker, LEP, 59.). Zanchi, OLG, 13-14. Philip Melanchthon, Commonplaces: Loci Communes 1521 (LC 1521), trans. Christian Preus (Saint Louis, MO: Concordia Publishing House, 2014), 62. It is worth noting that, if anyone doubts that Luther affirmed natural law, it is a well-known fact that Luther called this edition of Melanchthon’s Loci Communes, the most pure presentation of the Gospel outside of the Scriptures themselves. He thus indicated his agreement with Melanchthon on what he argues here. Melanchthon goes into much greater detail in the final edition of his Loci Communes (Philip Melanchthon, The Chief Theological Topics: Loci Praecipui Theologici 1559, trans. J. A. O. Preus, 2nd ed. (Saint Louis, MO: Concordia Publishing House, 2011), 89-137.).] Two other types of law, subordinate to natural and eternal law, are the jus gentium and positive or human laws.[5. Cf. Aquinas, ST I-II, qq. 91-96. Hooker, LEP, 50-63. Zanchi, OLG, 5-7. Heinrich Bullinger, The Decades of Henry Bullinger: the first and second decades, trans. H. I., ed. Thomas Harding (Cambridge: The University Press, 1850), 193. Melanchthon, LC 1521, 61, 65, 66, 77. James V. Schall, S. J., argues that the jus gentium should be situated somewhere between natural law and positive law (James V. Shall, S. J., “natural law and the Laws of Nations: Some Theoretical Considerations”, Fordham International Law Journal, vol. 15, iss. 4 (1991): 997-1030.). Others have suggested that it does not precede natural law, but that both flow out of natural law (Cf. Anton-Hermann Chroust, “The ‘Ius Gentium’ in the Philosophy of Law of St. Thomas Aquinas”, Notre Dame Law Review, Vol. 17, 1 (1941): 26-27.).] The jus gentium is essentially those laws which regulate international relations–the interactions between countries. What is called the divine law is generally taken to be God’s expressed law given to his elect. This hierarchy could be portrayed as follows.

Returning to natural law, we say that it is the rule, order, or norm of all human actions—in terms of what is right or wrong, good or evil. It is the eternal law as it is concerned with human beings—that is, the idea of human nature in the divine mind—and, therefore, it is normative for all human beings.[6. Cf. Aquinas, ST I-II, q. 91, a. 2, resp.; q. 93, a. 1, resp.; q. 93, a. 5, resp. David Haines & Andrew A. Fulford, Natural Law: A Brief Introduction and Biblical Defense (Lincoln, NB: Davenant Press, 2017), 5. Zanchi, OLG, 13-14. Torrance Kirby notes that, for Hooker, “The natural law is God’s means of preserving the order of the world once created; it is effectively the eternal law as kept by all creatures. (Torrance Kirby, “Richard Hooker’s Theory of natural law in the Context of Reformation theology”, The Sixteenth Century Journal, vol. 30, no. 3 (Autumn, 1999): 690.)” He later adds that, for Hooker, “By the unaided illumination of natural reason, it is possible to distinguish true from false, good from evil, and consequently a certain degree of knowledge of the divine will itself is attainable without the help of supernatural revelation. This natural knowledge of God consequently leads to a natural practical wisdom. To know theologically what human nature is and where it stands in the larger order of creation is the starting point for reflection upon the principles of human action (Kirby, “Richard Hooker’s Theory of natural law in the Context of Reformation theology”, 690-91.).”] It is engraved on human minds, and can be known through the rational consideration of the natural ends of humankind through consideration of human nature.

Returning through each of the elements just mentioned, we note, firstly, that both moral norms and the ability to know those norms, are grounded in human nature (as human nature is, first in the divine mind, and, second, as it is brought to be by God in sensible reality).[7. Cf. Bullinger, Decades: First and Second, 195.] Secondly, natural law, as a “law”, is a norm for all human actions, teaching what is right and wrong, and ordaining men to the good.[8. Cf. Aquinas, ST I-II, q. 93, a. 5, resp., Zanchi, OLG, 1-4. Hooker, LEP, 50, 73. Bullinger, Decades: First and Second, 195. Melanchthon, LC 1521, 61-62. John Calvin, Institutes of the Christian Religion (ICR), bk. 2, ch. 2, §22, trans. Ford Lewis Battles, ed. John T. McNeill (1996; repr., Louisville, KY: Westminster John Knox Press, 2006), 282. We will use standard notation for Calvin’s Institutes.] By this is not meant unbreakable laws like those of mathematics or logic, but a standard to which humans are held accountable and against which they are measured, but which they frequently disobey. Neither is natural law that which humans “naturally” think they should do, nor their own desires for what they perceive to be good, but, rather, that end towards which God, as the maker of mankind, ordains that man seek.

Thirdly, as law, it relates specifically to human actions, by which we distinguish it (a) from natural theology (that which can be known of God from man’s rational observations of the cosmos)—natural law is related to the good of man and right action, whereas natural theology is related to the truth, and knowledge;[9. Another way of explaining this is to say that natural law is related to “doing good”, and natural theology is related to “knowing truth.” This is a distinction which is not always made clear in literature on the subject, as some theologians include what can be known of God under natural law. Cf. Zanchi, OLG, 9.] and (b) from the laws of nature which govern the physical cosmos and all physical beings.[10. Cf. Zanchi, OLG, 12. Hooker, LEP, 54. Aquinas, ST I-II, q. 91, a. 2, ad 3.] In relationship to what can be known of natural law and how it is known, we say, fourth, (a) that it is knowable, in its general principles, by all human beings, though not all human beings necessarily arrive at propositional knowledge of its general principles;[11. Cf. Zanchi, OLG, 16, 17, 20, 21-23. Hooker, LEP, 77-79.] and (b) that it is knowable discursively through reflection on the final end of man, and, in a sometimes confused manner, intuitively.[12. Cf. Calvin, ICR, bk. 2, ch. 2, §22. Zanchi, OLG, 7, 14-17. Hooker, LEP, 71-79. Aquinas, ST I-II, q.  93, a. 5, resp. Many Reformers see it as “implanted knowledge (cf. Bullinger, Decades: First and Second, 194-95.).” Others, such as Hooker see it as a natural tendency towards the good, and known through a process of rational thought. Hooker says, for example, “These laws can be discovered through reason, even without divine revelation (Hooker, LEP, 76.)” Melanchthon agrees with Hooker, that these laws can be known via syllogism (Melanchthon, LC 1521, 61.).] However, due to the effects of sin on the human intellect and will, most people will arrive at knowledge of these principles, and obey them, only with difficulty.[13. Cf. Aquinas, ST I-II, q. 93, a. 6, resp. Zanchi, OLG, 12, 14-15. Zanchi appears to make the unique claim that original sin so annihilated human nature, that God was required to re-inscribe or re-write natural law on the heart of man after the Fall (Zanchi, OLG, 12, 14-16.).] As to the “content” of natural law, most Reformed theologians have suggested that natural law is basically summed up in the 10 Commandments.[14. Cf. Zanchi, OLG, 24. Beza, Job, ch. 1, 1. Luther, CR, 58-60.]

The biblical basis for natural law

“For when Gentiles, who do not have the law, by nature do what the law requires, they are a law to themselves, even though they do not have the law. They show that the law is written on their hearts, while their conscience also bears witness, and their conflicting thoughts accuse or even excuse them on that day when, according to my gospel, God judges the secrets of men by Christ Jesus.” (Romans 2:14-16)

Though there are many other texts in Scriptures which appeal to man’s natural knowledge of right action, or that point man towards either his own nature, or to creation itself, in order to learn how they should act, the most common biblical text to which Christian theologians have appealed in support of the notion of natural law is Romans 2:14-15.[15. Due to space constraints, we will only note a couple of key biblical texts, and their traditional interpretation. For more biblical support of natural law, see Haines and Fulford, NL, 50-115.] A second passage in Romans can also be taken to refer to natural law, “Though they know God’s decree that those who practice such things deserve to die, they not only do them but give approval to those who practice them (Rom. 1:32).” These verses have been traditionally[16. Some Protestant commentators who tend to affirm the traditional interpretation include: Douglas Moo, The Epistle to the Romans, NICNT (Grand Rapids, MI: Wm. B. Eerdmans, 1996), 148-53. John Murray, The Epistle to the Romans, NICNT (Grand Rapids, MI: Wm. B. Eerdmans, 1968), 72-75, 78. Charles Hodge, A Commentary on Romans (1835; repr., Edinburgh/Carlisle, PA: Banner of Truth Trust, 1975), 54-59. John Calvin, The Epistles of Paul the Apostle to the Romans and to the Thessalonians (EPART), trans. Ross Mackenzie, eds. David W. Torrance and Thomas F. Torrance (1960; repr., Grand Rapids, MI: Wm. B. Eerdmans Publishing Co., 1976), 58-60. Calvin, ICR, bk. 2, ch. 2, §22. Zanchi, OLG, 13-21. Hooker, LEP. Bullinger, Decades: First and Second, 193. Melanchthon, LC 1521, 61. Theodore Beza, Job (London: John Legatte, 1589), ch. 1, v.1. The great majority of patristic and medieval theologians also interpreted these verses in what we have called the traditional interpretation, even when, like Augustine, they offered alternative interpretations. In the first edition of his commentary on Romans, Thomas Schreiner adopted the traditional interpretation of Romans 2:14-16 (Thomas R. Schreiner, Romans, BECNT (Grand Rapids, MI: Baker Academic, 1998), 119-25.). More recently he has tentatively turned towards a different interpretation of Romans in which the Gentiles referred to are Christian gentiles keeping the Law of Moses by the work of the Spirit (Thomas R. Schreiner, Romans, 2nd ed., BECNT (Grand Rapids, MI: Baker Academic, 2018), 128-33.). Schreiner’s later position is one of the ways in which Augustine interprets these passages (Augustine, Spirit and the Letter 26.43-45.). However, Augustine also appeals to these verses as proof of natural law.] been understood to affirm that as human nature (a metaphysical structure) was created by God,[17. Sometimes this is expressed as such, sometimes the same sentiment is expressed as “by nature”, “from the creation of mankind”, or “from creation”. Cf. Martin Luther, Commentary on Romans, trans. J. Theodore Mueller (1976; repr., Grand Rapids, MI: Kregel Publications, 1979), 58, 60. Calvin, EPART, 48. Here, Calvin specifically says, “Paul contrasts nature with the written law, meaning that the Gentiles had the natural light of righteousness (my italics), which supplied the place of the law by which they Jews are taught, so that they were a law unto themselves (Calvin, EPART, 48.).” Bullinger, Decades: First and Second, 194.] all human beings have (a) moral inclinations towards good and away from evil, which are sometimes equated with conscience,[18. This has been a common interpretation of “written on their hearts” (Cf. Luther, CR, 58-60. Calvin, EPART, 48-49. Beza, Job, ch. 1, 1. Bullinger, Decades: First and Second, 193-94.). However, John Murray is certainly right to note that “conscience” here, is called in as a witness to the law written on their heart, not “as” the law written on their heart (Murray, ER, 75.).] and conscience, formed or deformed by our own actions and social surroundings, which points to good and away from evil; and (b) either actually possess knowledge of general moral tenets, or have the ability to learn them by inference from reasoned observations (epistemological structures); such that they either act rightly, and know it, or feel guilt when they act wrongly. Most pagans simply rebel against this law which is written on their hearts.

It is important to note, here, that the traditional interpretation of these passages affirms not only that there is such a natural knowledge of morality, but that man in fact has some knowledge (albeit imperfect) of it.[19. Cf. Luther, CR, 59. Calvin, EPART, 48-49. Zanchi, OLG, 20-23.] This does not mean, however, (1) that they have a perfect knowledge of it such that they can always formulate it in clear normative propositions of moral approval or disapproval (thou shall or thou shalt not).[20. Cf. Zanchi, OLG, 16, 21-23. Melanchthon, LC 1521, 62.] Nor does it mean, (2) that humans always successfully act rightly—rather, the purpose of these verses is to show that all humans are rightly condemned by God for moral laxity and unrighteousness, whether they had access to the written law of Moses or not.[21. Cf. Luther, CR, 58-59. Calvin, EPART, 48-49. Calvin, ICR, bk. 2, ch. 2, §22.] The basis for the just judgment of God is natural law.

The evidence for these nuances is two-fold: (a) the greatest pagan philosophers, such as Socrates, Plato, Aristotle, Seneca, and Cicero have articulated moral theories in which a great majority of what they praised or condemned is also praised or condemned in the moral teachings of Scripture;[22. Cf. Luther, CR, 58-60. Calvin, EPART, 48-49. Beza, Job, ch. 1, 1. Melanchthon, LC 1521, 62. We could point the interested reader to the works of Plato in general (of particular interest will be the Republic, where Plato not only affirms a number of important virtues, and the importance of justice, but seeks to demonstrate that it is good to be just for the sake of being just), Aristotle’s ethical writings (specifically the Nicomachean Ethics, which was a special favorite of Protestant professors, pastors, and reformers during the 16th and 17th centuries), and Cicero’s On the Nature of the Gods and On Moral Duties (which were favorites of most of the early Reformers, especially John Calvin).] and, (b) all pagan societies and peoples put some moral laws in place, punishing those who break them and rewarding those who obey them.[23. Cf. Luther, CR, 58-60. Calvin, EPART, 48-49. Zanchi makes the interesting claim that God used the great pagan lawmakers and philosophers to reveal the natural law to the pagan nations which had not received divine law through God’s inspired prophets and apostles (Zanchi, OLG, 6-7.).] In other words, Christian theologians find confirmation in human society of the truth claims of the inspired Scriptures. Christian theologians are not surprised to find pagans who, with no knowledge of the Bible, both know some moral truths and perform some right actions.

However, also based upon a right reading of Scripture, Christian theologians assume neither that pagans actually live up to the standards of natural law, nor that they are in any way justified by their actions.[24. Beza, Job, ch. 1, 1. Calvin, ICR, bk. 2, ch. 2, §22.] Rather, the whole point of these passages is to show that God is just when he condemns them, for, though they do not have the law of Moses, they are rightly condemned by the natural law for both idolatry and immorality. John Calvin in his exposition of these verses, concludes that “there is, therefore, a certain natural knowledge of the law, which states that one action is good and worthy of being followed, while another is to be shunned with horror.”[25. Calvin, EPART, 49.] Martin Luther’s conclusion resembles Calvin’s: “All of this proves that they know the Law by nature, or that they can distinguish between good and evil.”[26. Luther, CR, 60. Luther, throughout his commentary on Romans, clarifies that he is in agreement with Augustine on this subject.]

What does natural law teach and what is its use?

As noted above, Protestant theologians have traditionally taught that what God gave to Moses in the 10 Commandments is nothing more nor less than that which is known through nature.[27. Cf. Luther, CR, 58-60. Beza, Job, ch. 1, 1. Zanchi, OLG, 24.] This includes not only that God should be worshipped (and that there are forms of worship, such as child sacrifice, which are not acceptable), but also, that murder, adultery, stealing, and so on, are immoral, and should be punished by society in general.[28. Luther, CR, 58-60. Calvin, EPART, 48-49. Calvin says, for example, “there is imprinted on their hearts a discrimination and judgment, by which they distinguish (note: they actually do distinguish) between justice and injustice, honesty and dishonesty (EPART, 48).” Bullinger, Decades: First and Second, 193-95. Aquinas, ST I-II, q. 94, a. 2, resp.] Calvin, for example, says that “all the Gentiles alike institute religious rites, makes laws to punish adultery, theft, and murder, and commend good faith in commercial transactions and contracts. In this way they prove their knowledge that God is to be worshipped, that adultery, theft, and murder, are evils, and that honesty is to be esteemed.”[29. Calvin, EPART, 48.] The Swiss Reformer Heinrich Bullinger makes a similar point by noting that what is known as the golden rule is known through natural law. He goes on to quote some pagan authors who proposed moral principles which resemble it.[30. Bullinger, Decades: First and Second, 197. Aquinas seems to hold to a very similar position as that found in Bullinger, suggesting that the foundational principle of natural law is that men should do good and avoid evil. From this, he suggests we infer that God is to be worshiped, that we are to reproduce and fill the earth, and that we should avoid harming others (Aquinas, ST I-II, q94, a. 2, resp.).] This claim was common amongst the early Protestant reformers, Lutheran and Reformed alike.[31. Cf. Melanchthon proposes three foundational moral laws known via natural law: (1) That God should be worshiped, (2) that no harm should be done to human beings, and (3) that we should possess all things in common (Melanchthon, LC 1521, 63-66.).] 

A great example of this, based upon the notion that the general principles of natural law can be classified into the two parties concerned by the law in general—God and Man[32. Zanchi, OLG, 2-4. Bullinger articulates the exact same point, which may suggest that there is influence between Bullinger and Zanchi. Bullinger lays down the two following key points concerning natural law: “The first is, Acknowledge God, and worship him: the second is, Keep or maintain society and friendship among men. (Bullinger, Decades: First and Second, 196.).”]—is found in the work of the Italian Reformer Girolamo Zanchi, who goes on to provide a short list of moral principles that man can know through natural law, “Examples include what is God, how he should be worshipped, or other things pertaining to religion, as well as how one should obey one’s parents or the State or even how one should ward off injury, violence, or anything that relates to the defense and protection of oneself, one’s family, and the State.”[33. Zanchi, OLG, 9-10.] With these examples in hand, Zanchi then distinguishes the three main levels of natural law: (1) Self care – “First, people can protect themselves against any violence or injury…From this instinct comes the idea included in the laws of nations that it is permitted to repel force with force.”[34. Zanchi, OLG, 10.] (2) Familial responsibilities – clearly thinking of Genesis 1:28, Genesis 8:16-17, and the first books of Aristotle’s Politics, Zanchi argues that the second level of natural law involves the rearing and education of children—“marriage, reproduction, and rearing children under natural law.”[35. Zanchi, OLG, 11.] (3) Social and religious responsibilities – “human beings must recognize their inclination to God and worship him as they do good to those with whom they live, and they must know justice and honesty and turn to them naturally.”[36. Zanchi, OLG, 11.]

If, as we have argued, Protestants have traditionally believed that all men have natural knowledge of, at the very least, some general moral precepts (both intuitively and via reasoning); and if the 10 Commandments are a divinely inspired articulation of what should be naturally known; then, Protestants, in light of the 10 Commandments, can and should use natural law arguments in the public sphere to convince unbelievers of those moral truths which all men know, and by which all men are judged. natural law, then, can be used in the attempt to convince unbelievers of the immorality of abortion, infanticide, and euthanasia; to argue for the fact that there are only two biological sexes (male and female); to discuss those elements which make a war just or unjust, and so on. Protestants can appeal to the natural world and to human nature itself to support the truth that marriage (the union, recognized by church and state, of a biological man and a biological woman) is fundamental to society and should be protected; to argue against the morality of various sexually deviant behaviours; to defend the dignity of all human-beings, regardless of location, ethnicity, language, social status, occupation or any other non-essential property; and to defend the right stewardship of the entire sensible cosmos, neither elevating non-rational beings above humans, nor treating them irresponsibly.

In other words, Protestants can and should use natural law arguments to help society pursue and protect the common good of all people. By pursuing and protecting the common good of society, peace in the earthly realm is promoted and protected. This allows for the freedom peacefully and publicly to present the Gospel to all men, which all Christians should desire. As such, natural law can be used not only to promote civil goods, but also eternal good.

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