Adam Lloyd Johnson
Southeastern Baptist Theological Seminary,
Wake Forest NC USA
Published in the Canadian Journal for Scholarship and the Christian Faith (journal.ccscf.org) on 2 March 2016
Natural law reasoning has largely fallen out of favor among Protestants. J. Daryl Charles has observed that “…there exists across Protestantism a broad consensus that rejects the natural law as a metaphysical notion rooted in divine revelation.” This rejection of natural law among Protestants is due in no small part to the influence of Karl Barth. Stephen J. Grabill maintained that Barth’s influence was one of three factors that caused many Protestants to reject natural law during the twentieth century. While it is outside the scope of this paper to provide a complete response to Barth’s opposition to natural law, the purpose of this paper is to respond to one of his objections, namely, that natural law elevates human reason too highly.
Certainly we should be careful about putting too much confidence in our fallen human reason. But was Barth correct, does natural law elevate human reason too highly? The thesis of this paper contends that the modern version of natural law does elevate human reason too highly but the pre-modern does not.  Thus Barth’s rejection of natural law in toto was mistaken because he failed to distinguish between these two versions of natural law, the modern and the pre-modern. By ignoring this distinction, Barth mistakenly rejected both whereas he should have only rejected the modern version.
In order to make this argument, I will first make a brief biblical case for using natural law reasoning in the public square so as to set the context for the discussion. In part two I will explain Barth’s key objection to natural law, that it elevates human reason too highly. Finally, in part three, I will respond to his rejection, showing that the modern version of natural law does make this mistake but the pre-modern version does not.
A Biblical Case for Natural Law
In this section I will make a brief biblical case that using natural law reasoning is an appropriate method of trying to influence the public square, that is, of trying to influence fallen governmental leaders to adopt and enforce morally good laws. In Rom. 13:1-4, Paul wrote that government is an “authority… established by God” which is supposed to “praise” those who “do what is good” and to be a “cause of fear… for evil [behavior]” (Rom. 13:1-4). Peter also wrote that the functions of government include the “praise of those who do right” and the “punishment of evildoers” (1 Pet. 2:14). Paul explained that government is a “minister of God” for suppressing evil and administering justice; it “bears the sword” to discourage evil behavior through the threat, and application, of punishment and is “an avenger who brings wrath on the one who practices evil” (Rom. 13:4).
These verses imply that fallen governmental leaders can know enough about morality such that they can, even without Scripture, correctly praise good behavior and punish evil behavior. In the above verses both Paul and Peter were referring to the Roman government, a government which was certainly not founded on biblical principles. Morris noted that “Paul is writing about the existing state, not some ideal state that he hoped would appear.” How is it then that such fallen governmental leaders, without Scripture, could know enough about morality such that they could be “minister[s] of God” in praising good and punishing evil?
The answer is found earlier in Romans where Paul explained that “Gentiles who do not have the Law do instinctively the things of the Law… they show the work of the Law written in their hearts” (Rom. 2:14-15). What is translated here as “instinctively” is the Greek word φύσει, which BDAG defines in this context as “the regular or established order of things, nature.” Hence this moral knowledge that Scripture attributes to fallen humanity has often been called natural law. In Robert Mounce’s explanation of these verses, he wrote that “…[w]henever Gentiles by natural instinct did what the law required, they demonstrated the existence of a guiding principle within themselves… their conduct revealed a general knowledge of God’s requirements for a principled and virtuous life.”
John Calvin affirmed this understanding of natural law, that it provides sufficient moral knowledge to fallen humanity such that they can develop good moral laws. He wrote:
Since man is by nature a social animal, he is disposed, from natural instinct, to cherish and preserve society; and accordingly we see that the minds of all men have impressions of civil order and honesty. Hence it is that every individual understands how human societies must be regulated by laws, and also is able to comprehend the principles of those laws. Hence the universal agreement in regard to such subjects, both among nations and individuals, the seeds of them being implanted in the breast of all without a teacher or lawgiver.
While arguing against those who thought every society should base their laws on the Law of the Old Testament, Calvin explained that societies were able to craft good laws without the Old Testament. In the midst of his explanation he appealed to the notion of natural law:
As constitutions have some circumstances on which they partly depend, there is nothing to prevent their diversity, provided they all alike aim at equity as their end. Now, as it is evident that the law of God which we call moral, is nothing else than the testimony of natural law, and of that conscience which God has engraved on the minds of men, the whole of this equity of which we now speak is prescribed in it. Hence it alone ought to be the aim, the rule, and the end of all laws. Wherever laws are formed after this rule, directed to this aim, and restricted to his end, there is no reason why they should be disapproved by us, however much they may differ from the Jewish law, or from each other.
If Rom. 13:1-4 implies that fallen governmental leaders can have true moral knowledge, and if this knowledge is explained by natural law as seen in Rom. 2:14-15, then it is reasonable to conclude that natural law reasoning would be effective in influencing fallen governments to correctly praise what is good and punish what is evil.
What does an appeal to natural law look like? First of all, it is not an argument merely for the term natural law. The term itself is incidental; what matters is the concept behind the term. In fact, because the term natural law has been used to describe so many different things, some of which are diametrically opposed to one another, Russell Hittinger recommends the term higher law, as employed by Martin Luther King, because it “indicates the more than human ground for the public moral order.” In other words, an appeal to natural law is an appeal to a moral order that is above us, that is, greater than our own personal preferences and man-made laws, something to which all persons and man-made laws are accountable to and should be judged by.
Evaluating a moral issue from a natural law perspective can include, but is not limited to, considering the utilitarian consequences of the behavior in question, both for the individual and for society. It is appropriate to consider these factors because God has built moral consequences into the fabric of the universe such that we reap what we sow (Gal. 6:7). Thus we should expect immoral behavior to lead to ill effects. Though consequences are important to consider, ultimately natural law arguments are an appeal to the objective moral law that is written on fallen hearts (Rom. 2:14), something we as Christians know is there even if they do not. In this sense, appealing to natural law is simply reminding people of what God says they already know.
It is important to note that natural law proponents are not against using special revelation in the public square as well. Here I am only making the case for the use of natural law but it is important to remember that this is not mutually exclusive with also using special revelation. Special revelation is superior in many respects, but, if it is not recognized by the government you are trying to influence, then natural law may possibly be more effective in such a context. For example, William Edgar wrote:
…an appeal to Scripture in the public square is not always a wise strategy. But this is a strategic choice, not the preference of one kind of revelation over another… The basis of our hope is not that one kind of revelation will ‘work’ better than another but our knowledge that this is Christ’s world and that, whether magistrates like it or not, they are appointed by him to do his will. To work in politics with this assumption does not mean awkwardly to draw the sword of the Bible at every point but to remind fellow politicians of what they know already, by virtue of general revelation.
Of course we should be careful lest the church become distracted from its primary mission of making disciples. Whereas government’s mandate concerns external behavior, the church should be focused on the heart, that is, on winning people to faith in Christ and helping them love and obey Him. Christ instructed the church to “make disciples of all nations” by evangelism (entailed in “baptizing them in the name of the Father and the Son and the Holy Spirit”) and by discipleship, that is, by “teaching them to observe all that I [Christ] commanded” (Matt. 28:19-20). Though Christians should primarily be involved with the church, helping it accomplish its mission of making disciples, they should also be concerned that the government fulfills its God given purpose of providing order and stability to society.
I am only arguing that Christians in general should want to see the government fulfill its God given task. Of course each individual Christian’s involvement in the government, just like their involvement in the church, will vary based on their specific gifting and calling. Christians who have been called to this specific ministry should be involved in informing and influencing fallen governments about what is right and wrong so as to help society be as safe and stable as possible. Other Christians should support and encourage them in this, not only for their own benefit, but to be a good neighbor to those around them. This is especially the case when it comes to protecting innocent people from harm and caring for those who cannot care for themselves, as Christ taught us through the parable of the Good Samaritan (Lk. 10:25-37). According to Rom. 13:1-4 and Rom. 2:14-15, natural law would seem to be a plausible approach for trying to influence fallen governmental leaders to adopt and enforce good moral laws.
A Common Objection to Natural Law
One of the most common objections that Protestants have raised against natural law is that it elevates human reason too highly. Jean Porter notes that this was a primary concern for Karl Barth in his “well-known critique of natural theology, which implies a rejection of any version of a natural law theory.” Porter continued by summarizing Barth’s objection as follows:
…we cannot attain reliable knowledge of God’s creation, and for this reason, we cannot draw reliable ethical conclusions from our partial and flawed knowledge of the created world… any moral system (whether pre-reflective or philosophical) that claims to offer clear, systematic, and self-contained guidance on matters of good and evil is fundamentally an expression of pride. It presupposes a degree of independent discernment that the human person cannot attain, and it reflects the human desire to attain justification and security independently of God, over against God.
Nigel Biggar also noted that “[o]ne (typically Protestant) reason that Barth gives for this [rejecting natural law] is epistemological. The concepts to which he refers are, he believes, tied to a high estimation of the power of human reason to apprehend the command of God the Creator directly in ‘reality’… Natural reason cannot perceive ‘with increasing certainty and clarity’ the order or many orders of creation, both because ‘reality’ is too obscure and because natural reason is too feeble.”
Barth often labeled natural law as a Roman Catholic doctrine, which had the effect of frightening many evangelicals away from it. For instance, he wrote that the “idea of a synthesis and continuity between nature and supernature” was “an idea which ruined the ancient Catholic Church and which signified a repenetration of the church by paganism.” He was concerned that this elevation of human reason had crept into Protestantism. David VanDrunen noted that Barth’s critique was “forged most immediately by his own rejection of the nineteenth-century Protestant liberal theology or culture Protestantism in which he was trained. He saw the earlier tradition’s acceptance of natural law and two kingdoms doctrines as serious flaws that had opened the door to many fundamental errors of recent Protestant theology.”
Barth viewed the revelation in Christ as the sole authority for theological understanding, seeing anything outside of that framework as a threat to Christ’s supremacy. Claiming to find truth through any means but Christ was heretical; Biggar described Barth’s view well when he wrote that “…only when we know about the grace of God in Jesus Christ do we know for certain what creation is, who the Creator is, and what it means to be the creature of this Creator.” Trying to understand creation apart from Christ elevates human reason and draws attention away from Scripture. Charles summarized this aspect of Barth’s theology as follows: “The preoccupation with ‘nature’ and ‘reason’… prepares the soil for a secularized humanism that empties Christian faith of its substance and undermines or denies the absolute lordship of Christ… it facilitates the emergence of a ‘natural religion’ and ‘natural theology’ that serve as a substitute for a ‘Word of God’ – centered and christocentric faith.”
For Barth, it made no difference that natural law proponents affirmed special revelation and even developed their view from Scripture. In his Church Dogmatics, concerning natural law, he wrote:
It is no help… that it tries to pay attention not only to the natural light of reason, but also to the light of revelation, and therefore from the very outset to give the desired theological shape and finish to the determination of man. Nor, again, is it any help… that it tries to focus attention on the light of revelation and only incidentally attends also to the natural light of reason… everything is compromised by the fact that revelation is not really accepted as revelation, but is constantly set against the light of reason with its independent, if limited, illumination.
If human reason is included then somehow this invalidates revelation; he wrote that “[g]race which has from the start to share its power with a force of nature is no longer grace… revelation which has from the very outset a partner in the reason of the creature, and which cannot be revelation without its co-operation, is no longer revelation.” Barth went so far as to claim that such a view is not even Christian when he wrote that this system of thought “thinks it can combine and co-ordinate the Christian and the human far too easily. To achieve this combination and co-ordination it has emptied out what is Christian.”
Barth’s disdain for natural law is most clearly seen in his critique of Emil Brunner’s argument for natural theology. Charles noted that “[e]ver since the Barth-Brunner controversy Protestant theology has been riddled with suspicion and skepticism vis-à-vis natural law. In this regard, it would appear that the influence of Barth has been dominant.” For example, Barth’s influence can be clearly seen in the work of Jacques Ellul; he wrote that “[i]f one adopts a strictly biblical view, then it would seem that one could hardly do otherwise than to follow Karl Barth on the subject of the impossibility of the natural knowledge of God by man, which leads to the same impossibility for the knowledge of the good.”
A Response to Barth’s Objection to Natural Law
In this section I will argue that Barth’s rejection of natural law came in part from a failure to distinguish between the modern version of natural law and the pre-modern version. Just because human reason was elevated too highly in the former does not mean we should therefore reject the latter.
The distinctive element of a pre-modern view of natural law, exemplified by Thomas Aquinas, is that morality is ontologically grounded in God’s nature. Aquinas used the term eternal law to describe the overall order and purpose which originates in God and governs all of His creation. He wrote that “it is evident that all things partake somewhat of eternal law in so far as, namely from its being imprinted on them, they derive their respective inclinations to their proper acts and ends.” This eternal law was imprinted by God on everything He created, including human beings, giving each individual thing an inclination towards its proper purpose. Aquinas explained that natural law comes about when people correctly perceive elements of this eternal law and act according to it. In reference to Rom. 2:14, he continued:
Wherefore it [the rational creature] has a share of the Eternal Reason, whereby it has a natural inclination to its proper act and end: and this participation of the eternal law in the [very nature of the] rational creature is called the natural law… the light of natural reason, whereby we discern what is good and what is evil, which is the function of the natural law, is nothing else than an imprint on us of the Divine light. It is therefore evident that the natural law is nothing else than the rational creature’s participation of the eternal law.
Understood this way, natural law is a form of general revelation; it is truth that originates from God and is revealed to us internally through the moral law on our hearts and externally through the order of His creation.
The important thing to note is that, in this pre-modern view of natural law, moral precepts do not originate from human reason. We can only know moral truth because, first, God wrote it on our hearts, and second, our God-given reason allows us to discern the proper purposes He imprinted on His creation. The pre-moderns were very clear that they believed God was the author of these moral precepts, not human reason or ingenuity. Just because our reason helps us discover them, this does not mean human reason is first in the causal order of their existence. We can discover this moral truth through reason, at least to some degree, because God gave us this ability and because He revealed it to us generally in His created order.
This is in contrast with a radically different view of natural law which developed later during the modern era. As western intellectual history progressed, more and more emphasis was placed on what could be known by human cognition alone. By the time of the Enlightenment, many thinkers were appealing first and foremost to the authority of human reason, i.e. what was first in the mind. These men separated natural law from its theistic ontological foundation and yet tried to build similar moral principles purely from autonomous human reason. To them, human reason, from which moral knowledge comes, is autonomous in the sense that it is not necessary for it to be grounded in, or even connected with, God and His work in creation. They thought human reason would still function reliably, and hence be able to develop moral principles, even if God did not exist. For example, Hugo Grotius wrote that the ability to understand justice “would have a place even were we to accept the infamous premise that God did not exist or did not concern himself with human affairs.”
During the modern era, the concept of natural law became interwoven with autonomous human reason, i.e. the belief that human beings are able to know truth on their own apart from God. For example, Thomas Hobbes explicitly taught that we ourselves make the principles of morality:
Politics and ethics (that is, the sciences of just and unjust, of equity and inequity) can be demonstrated a priori; because we ourselves make the principles—that is, the causes of justice (namely, laws and covenants)—whereby it is known what justice and equity, and their opposites injustice and inequity, are. For before covenants and laws were drawn up, neither justice nor injustice, neither public good nor public evil, was natural among men any more than it was among beasts.
As this view of ethics gained dominance, natural law became associated with the idea that people should be free from all laws except those they impose on themselves. Hittinger explained that “[v]irtually all of the Enlightenment ‘state of nature’ scenarios make this move. In Hobbes, Locke, Rousseau, and Kant, man is considered in an ‘original’ position, under the authority of no pope, prince, or scripture. If there is a God, he governs through no mundane authority. Authority will have to make its first appearance in the covenants of individuals constrained to reach a consensus on the basis of what is (or seems) self-evident.”
Thus we see an explicit and key difference between these two views of natural law, the pre-modern and the modern. Those who hold to a pre-modern view of natural law acknowledge that there is a proper role for human reason in discovering what is true whereas modern natural law proponents elevate reason to such an extent that it becomes the authority for deciding what is true. Charles explained that “[h]uman beings cannot avoid or deny their true nature, which due to the imago Dei seeks order. Natural theology, then, properly understood, concerns creation and cosmic reality, not human autonomy.”
Barth failed to recognize this important distinction in his most scathing polemic against natural law when he critiqued Brunner’s position, which is more reflective of a pre-modern view. Brunner wrote that “[e]ven fallen man still has — thanks to the ‘portion’ of the imago that he has retained — an immortal soul, a conscience, in which the law of God is indelibly and irremovably implanted. But he also has an inclination towards truth and a capacity for recognizing truth.” In spite of Brunner’s explicit explanation to the contrary, Barth repeatedly accused him of claiming that man is the one who decides what is right or wrong. Barth confused the issue when he argued that attributing to fallen man any ability to know moral truths makes him the decider of what is good and evil. He also associated Brunner’s emphasis on rationality with the rationalism of modernism, seeing him as “a representative of the ‘rational orthodoxy’ of the late seventeenth or early eighteenth century who had risen again and was speaking to us in modern terms.”
Barth mistakenly associated Brunner’s pre-modern position on natural law with the modern view of it. This is a common occurrence by Protestants who object to natural law; Mark Liederbach noted that reluctance among Protestants to embrace natural law:
…is largely due to how the doctrine of natural law eventually developed in light of some of the epistemological claims of Modernity… The Christian view that human rationality is embedded in the created order and directly dependent upon a coherence with the mind of God was eventually replaced by a view of autonomy and an over-simplified view of the ability of humans to reason and discover ‘truth’ apart from God. This is significant because so many of the modern preconceptions about natural law ethics assume that what is meant by a ‘natural law theory’ is a system of morality that claims a moral authority in nature that is somehow distinct from God himself. That is, there is a tendency to associate natural law with a kind of moral rationalism that excludes any appeal to direct theological grounds.
One of the reasons Barth saw pre-modern natural law and modern natural law so closely connected is because he thought the former was the root cause which led to the latter. Barth tried to draw a straight line from Aquinas, through the Enlightenment, to modern Protestantism. He wrote:
…[the Reformers] were not in a position to foresee all the reservations with which Roman Catholic theology has since, i.e. since the rediscovery of St. Thomas, learnt to surround its (materially unchanged) definitions. For the substance of these definitions has since, in an idealist form, i.e. in that of a secularized Thomism (which has found its mature form in Schleiermacher’s Glaubenslehr—E.T. The Christian Faith), but without consciousness of its real connections, become part of the armoury of modernist Protestantism.
I agree with Barth that modern natural law—that man through reason can decide what is true—is dangerously wrong, the very height of sinful fallen pride, and something that we should always be on guard against. But I disagree that the blame for this modern view can be placed upon pre-modern natural law, as exemplified by Aquinas, which held that man can merely discover truth to some degree. Pre-modern natural law did not inexorably lead to the exaltation of human reason as seen in modern natural law. Instead, the key breakdown occurred later when modernism broke nature away from its theistic metaphysical roots. In other words, the only reason that pre-moderns thought people could discover truth in nature was because they believed it was created by God. This is a most reasonable assumption and, as I argued above, what Scripture itself teaches.
One reason the modern movement exploded so powerfully was because people really did discover some truth in nature, as Scripture indicated they should. These thinkers were able to discern moral principles to some degree through reason and nature, as explained by Rom. 2:14. But the mistake of modernism, which came to full fruition in the Enlightenment, was to think that nature would still communicate moral truth even if God had not created it, that is, even if God did not exist. Daniel Heimbach noted that “rationalists of the seventeenth and eighteenth centuries… severed natural law from supernaturalism.” He continued by noting that “[t]his enlightenment version of supernaturally detached natural law philosophy… venerated reason.” It was not the pre-modern concept of natural law, but this Enlightenment view of nature, as completely autonomous from God, which have birth to modern natural law.
Barth and other Protestant theologians who rejected natural law were not the first to set up a dichotomy between faith and reason. It was the philosophers and writers of the early modern era and the Enlightenment who first established this dichotomy, over-emphasizing the side of reason. Barth and company mistakenly adopted this false dichotomy but instead over-emphasized the other side, the side of faith. They correctly discerned that too much emphasis had been put on reason but instead of rejecting the dichotomy, they overreacted and in turn put too much emphasis on faith to the exclusion of reason. They should have rejected the dichotomy altogether and returned back to the pre-modern synthesis between faith and reason found in Aquinas and the Reformers.
With Barth’s methodology, experiential faith is emphasized to such a degree that it becomes disconnected from objective reality, including any attempt at natural theology. He accused Brunner’s position, i.e. connecting faith with objective reality, of being unspiritual, as though reason and rationality are unspiritual. He also praised Kierkegaard and Heidegger, thinkers who spearheaded this methodology of revelatory experience. This method of emphasizing the subjective experience over objective reality substantially alters the definition of what truth is. It leads to a separation of historical and scientific truth, truth which is objectively true for everyone, from religious truth, which can be true for one person and not true for another, a view now rampant throughout western culture. Faith has become for many just a subjective feeling that is separated from objective reality, as though faith was merely a personal spiritual experience.
According to Scripture, government helps stem the tide of evil in society, evil which flows from our fallen hearts; for “out of the heart come evil thoughts, murders, adulteries, fornications, thefts, false witness, slanders” (Matt. 5:19). One of the important functions of government is to quell this destructive behavior by praising good and punishing evil. Christians should be concerned that the government perform its role well, not only for their own benefit, but so that society at large can enjoy greater safety and stability. In addition, Scripture indicates that fallen governmental leaders know enough about morality in order to perform their tasks. A reasonable explanation for their moral knowledge is the notion of natural law, as described by Paul in Rom. 2:14-15. Thus it seems that using natural law reasoning should be an appropriate and effective method of trying to influence fallen governmental leaders to adopt and enforce morally good laws.
The objection to natural law that I have considered in this paper, that it elevates human reason too highly, is certainly justified when it comes to the modern version of natural law which sees human reason as the decider of what is right or wrong. But it is a mistake to associate all natural law positions with this modern view. It is an overreaction to reject the pre-modern view of natural law because of modernism’s distortion of it. Certainly we should guard against elevating fallen man too highly, but we do not want to go to the other extreme and denigrate him more than Scripture does lest we, as Charles warned, bury the wrong corpse.
Aquinas, Thomas. A Summa of the Summa. Edited by Peter Kreeft. San Francisco: Ignatius Press, 1990.
Balz, Horst, and Gerhard Schneider, eds. Exegetical Dictionary of the New Testament. 3 vols. Grand Rapids, Mich.: Eerdmans, 1990.
Barth, Karl. Ethics. Edited by Dietrich Braun. Translated by Geoffrey W. Bromiley. New York: Seabury Press, 1981.
———. The Doctrine of God. Edited by Bromiley, G.W. and Torrance, T.F. Vol. II, part 2. Church Dogmatics. Edinburgh: T. & T. Clark, 1957.
Biggar, Nigel. The Hastening That Waits: Karl Barth’s Ethics. New York: Oxford University Press, 1993.
Brunner, Emil, and Karl Barth. Natural Theology: Comprising Nature and Grace by Professor Dr. Emil Brunner and the Reply No! By Dr. Karl Barth. Translated by Peter Fraenkel. Eugene, Or.: Wipf and Stock Publishers, 2002.
Budziszewski, J. What We Can’t Not Know: A Guide. Rev. ed. San Francisco: Ignatius Press, 2011.
Calvin, John. Institutes of the Christian Religion. Translated by Henry Beveridge. Peabody, Mass.: Hendrickson Publishers, 2008.
Charles, J. Daryl. Retrieving the Natural Law: A Return to Moral First Things. Grand Rapids, Mich.: William B. Eerdmans Publishing, 2008.
Danker, F. W., W. Bauer, W. F. Arndt, and F. W. Gingrich. A Greek-English Lexicon of the New Testament and Other Early Christian Literature. 3d ed. Chicago, Ill.: University of Chicago Press, 2000.
Edgar, William. Evangelicals in the Public Square: Four Formative Voices on Political Thought and Action. Edited by J. Budziszewski. Grand Rapids, Mich.: Baker Academic, 2006.
Ellul, Jacques. To Will and to Do: An Ethical Research for Christians. Translated by C. E. Hopkin. Philadelphia, Penn.: Pilgrim Press, 1969.
Grabill, Stephen J. Rediscovering the Natural Law in Reformed Theological Ethics. William B. Eerdmans Publishing Co., 2006.
Grotius, Hugo. Right of War and Peace in From Irenaeus to Grotius: A Sourcebook in Christian Political Thought 100-1625. Edited by Oliver O’Donovan and Joan Lockwood O’Donovan. Grand Rapids, Mich: William B. Eerdmans Publishing Co., 1999.
Heimbach, Daniel. “Natural Law in the Public Square.” Lib. Univ. Law Rev. 2:305 (2008): 685–701.
Hittinger, Russell. A Preserving Grace: Protestants, Catholics, and Natural Law. Edited by Michael Cromartie. Grand Rapids, Mich.: William B. Eerdmans Publishing Company, 1997.
Hobbes, Thomas. Man and Citizen. Edited by Bernard Gert. Indianapolis: Hackett Publishing Company, 1991.
Liederbach, Mark. “Natural Law and the Problem of Postmodern Epistemology.” Lib. Univ. Law Rev. 2:305 (2008): 777–92.
Morris, Leon. The Epistle to the Romans. The Pillar New Testament Commentary. Grand Rapids, Mich.: William B. Eerdmans Publishing Company, 1988.
Mounce, Robert H. Romans. NAC 27. Nashville, Tenn.: Broadman and Holman Publishers, 1995.
Porter, Jean. Natural and Divine Law: Reclaiming the Tradition for Christian Ethics. Grand Rapids, Mich.: William B. Eerdmans Publishing Company, 1999.
VanDrunen, David. Natural Law and the Two Kingdoms: A Study in the Development of Reformed Social Thought. Grand Rapids, Mich.: William B. Eerdmans Publishing Company, 2009.
 J. Daryl Charles, Retrieving the Natural Law: A Return to Moral First Things (Grand Rapids, Mich.: William B. Eerdmans Publishing, 2008), 111.
 Stephen J. Grabill, Rediscovering the Natural Law in Reformed Theological Ethics (William B. Eerdmans Publishing Co., 2006), 21–54.
 Certainly there were several versions of natural law in pre-modern times, as well as in modern times. But for the purpose of this paper, I will use the terms ‘pre-modern natural law’ and ‘modern natural law’ broadly in order to highlight the pertinent differences between (i) what most pre-modern versions share in common and (ii) what most modern versions share in common.
 All scriptural references are taken from the NASB version unless otherwise noted.
 Leon Morris, The Epistle to the Romans, The Pillar New Testament Commentary (Grand Rapids, Mich.: William B. Eerdmans Publishing Company, 1988), 459.
 Danker et al., A Greek-English Lexicon of the New Testament and Other Early Christian Literature, 3d ed. (Chicago, Ill.: University of Chicago Press, 2000), 1070.
 Robert H. Mounce, Romans, NAC 27 (Nashville, Tenn.: Broadman and Holman Publishers, 1995), 95.
 John Calvin, Institutes of the Christian Religion, trans. Henry Beveridge (Peabody, Mass.: Hendrickson Publishers, 2008), 166.
 Ibid., 980.
 Russell Hittinger, A Preserving Grace: Protestants, Catholics, and Natural Law, ed. Michael Cromartie (Grand Rapids, Mich.: William B. Eerdmans Publishing Company, 1997), 29.
 J. Budziszewski, What We Can’t Not Know: A Guide, Rev. ed. (San Francisco: Ignatius Press, 2011).
 William Edgar, “Francis Schaeffer and the Public Square,” in Evangelicals in the Public Square: Four Formative Voices on Political Thought and Action (ed. J. Budziszewski; Grand Rapids, Mich.: Baker Academic, 2006), 185.
 Jean Porter, Natural and Divine Law: Reclaiming the Tradition for Christian Ethics (Grand Rapids, Mich.: William B. Eerdmans Publishing Company, 1999), 169.
 Nigel Biggar, The Hastening That Waits: Karl Barth’s Ethics (New York: Oxford University Press, 1993), 54.
 Karl Barth, Ethics, ed. Dietrich Braun, trans. Geoffrey W. Bromiley (New York: Seabury Press, 1981), 14.
 David VanDrunen, Natural Law and the Two Kingdoms: A Study in the Development of Reformed Social Thought (Grand Rapids, Mich.: William B. Eerdmans Publishing Company, 2009), 318.
 Biggar, The Hastening That Waits, 54.
 Charles, Retrieving the Natural Law, 128.
 Karl Barth, The Doctrine of God, ed. Bromiley, G.W. and Torrance, T.F., vol. II, part 2, Church Dogmatics (Edinburgh: T. & T. Clark, 1957), 533.
 Ibid., 531.
 Ibid., 534.
 Emil Brunner and Karl Barth, Natural Theology: Comprising Nature and Grace by Professor Dr. Emil Brunner and the Reply No! By Dr. Karl Barth, trans. Peter Fraenkel (Eugene, Or.: Wipf and Stock Publishers, 2002), 1.
 Charles, Retrieving the Natural Law, 131. For specific examples of how Barth influenced Protestant theologians against natural law, see p. 134 concerning Jacques Ellul and p. 139 concerning John Howard Yoder.
 Jacques Ellul, To Will and to Do: An Ethical Research for Christians, trans. C. E. Hopkin (Philadelphia, Penn.: Pilgrim Press, 1969), 6.
 Thomas Aquinas, A Summa of the Summa, ed. Peter Kreeft (San Francisco: Ignatius Press, 1990), 504.
 Hugo Grotius, Right of War and Peace in From Irenaeus to Grotius: A Sourcebook in Christian Political Thought 100-1625, ed. Oliver O’Donovan and Joan Lockwood O’Donovan (Grand Rapids, Mich: William B. Eerdmans Publishing Co., 1999), 794.
 Thomas Hobbes, Man and Citizen, ed. Bernard Gert (Indianapolis: Hackett Publishing Company, 1991), 42–43.
 Hittinger, A Preserving Grace, 9–10.
 Charles, Retrieving the Natural Law, 153.
 Brunner and Barth, Natural Theology, 68, 72.
 Ibid., 42. Emphasis mine.
 Ibid., 86. See other examples on 109, 118, 120, and 121.
 Ibid., 110.
 Mark Liederbach, “Natural Law and the Problem of Postmodern Epistemology,” Liberty University Law Review 2:305 (2008): 783.
 Brunner and Barth, Natural Theology, 94.
 Ibid., 101.
 Daniel Heimbach, “Natural Law in the Public Square,” Liberty University Law Review 2:305 (2008): 694.
 Brunner and Barth, Natural Theology, 128.
 Ibid., 114.
 Charles, Retrieving the Natural Law, 153.