Spies are not “moral philosophers measuring everything they do by the word of God.”1 The world of secret intelligence is notoriously ambiguous, complex, and opaque. This article presents a framework for Christian engagement in government intelligence agencies by evaluating the extent to which the theology of Thomas Aquinas informs such involvement.2 Following recent discussion upholding Paul’s valuation of all work undertaken by Christians and the distinction between “work for the Lord” and “work for the kingdom” of God in Colossians, with the help of Aquinas we consider the appropriateness of Christian work for the Lord in the particularly complex realm of intelligence operations.3

Evaluating Aquinas is worthwhile given his “disproportionate influence” on natural law thinking and because his articulation of just war theory “climaxed a thousand years of Christian speculation on war.”4 Following a year in which the horrendous reality of war has been felt again in Europe, appreciating Aquinas’s contribution in this area is germane for both the church and Christians engaged in the public square.

In our evaluation of this topic, (1) we make brief methodological remarks concerning the application of Aquinas’s work to this contemporary issue. (2) Then we consider Aquinas’s public theology by surveying four key pillars of his thought: political authority, natural law, the distinction between natural and supernatural goods, and the differentiation between theological and cardinal virtues. Building on these foundations, we consider their application to issues of (3) war and (4) deception. (5) We conclude by assessing how this analysis informs the possibility of Christian engagement in intelligence operations.

1. Challenges Concerning the Application of Aquinas’s Theology to Intelligence Work

In applying Aquinas’s theology to the field of intelligence work, two challenges emerge. First, Aquinas’s historical context is dissimilar from our own, not least with the recent emergence of significant technological developments and sophisticated intelligence agencies. Some of the challenges faced by Christians working in this sphere would have been unthinkable to our great grandparents, let alone Aquinas. One example would be the rise of the internet, enabling “the rise of an anarchic international order.”5 Second, evaluating Aquinas’s thought on war, where his treatment of this issue is relatively brief, requires synthesis from across his writings before making careful contemporary application.6

2. Identifying Key Pillars of Aquinas’s Thought That Inform Christian Engagement in the Public Square

To establish Aquinas’s framework for Christian engagement in the public square, we consider four salient pillars of his thought: politics, natural law, natural and supernatural goods, and virtues. These are just some of the many significant contributions that Aquinas has made to theology, epistemology, and ethics. However, these four are the ones pertinent to this article.7

2.1. Politics

In the first pillar, we observe two important emphases of Aquinas’s political theory. First, Aquinas viewed political power positively, affirming its “original, pre-lapsarian goodness.”8 Since man is “by nature a political and social animal,” some form of political power was needed, even before sin.9 Consequently, the purpose of politics exceeds restraint of sin, affording dignity to broader Christian engagement in the political realm. This is not to suggest that serving in public office for the purpose of restraining evil does not have dignity, but is to recognize that the exercise of political power is not attributable solely to the fall. While Augustine emphasized political power as a post-lapsarian necessity, Aquinas upheld the “naturalness of political society.”10 However, these differences should not be overplayed since their two contrasting emphases later “converged upon a consensus, that while powers of association, organisation, and management are among the creaturely possibilities of human existence, the crystallisation of these into political functions of command and restraint presupposed a threat to human existence.”11

Second, although Aquinas’s conception of the relationship between church and state was complex, in De Regno he summarised three central facets of the king’s role.12 These were first, “establish the good life of the community,” second, defend the community, which included authority to punish criminals and wage war, both consequences of the fall, and third, ensure the community’s improvement.13

2.2. Natural Law

The second and most significant pillar of Aquinas’s thought pertaining to this article is his understanding of natural law. Of the four pillars, we spend the longest establishing the foundation for natural law, given its importance for our subject, complexity, and extent to which it has been contested. We consider four aspects of Aquinas’s view: his understanding of law, definition of natural law, his view of natural law’s relationship to human law, and its relationship to the Mosaic law. Finally, we consider the ways in which natural law provides a helpful perspective for public theology.

First, Aquinas defined law as “an ordinance of reason for the common good of a community made by the authority who has care of the community and promulgated.”14 Aquinas identified four types of law: eternal, natural, human (positive), and divine. We turn to the definition of natural law below, but we briefly observe Aquinas’s definitions of the other types of law. Eternal law is defined as “the ruling idea of things which exists in God as the effective sovereign of them … the whole community of the universe is governed by God’s mind.”15 Natural law is the “sharing in the eternal law by intelligent creatures.”16 Human (positive) law is the “specific arrangements human reason arrives at … [derived] from natural law precepts.”17 Geisler comments on human law, “It is a particularisation of the general principles of natural law.”18 Divine law “primarily directs man … that he may cling to God,” consisting of biblical revelation.19 Aquinas’s account “beautifully exhibits the various dimensions of ordering wisdom.”20

Second, building on the definition above, natural law is a teleological “moral order,” “direct[ing] people toward proper human goals.”21 It consists of “primary” and “secondary precepts.”22 Fundamentally, natural law provides the universal basis by which all humanity “is aware … of what is good and what is bad,” as is often argued from Rom 2:14–15.23 As Geisler observes, “all rational creatures share in the natural law. It is the law written on their hearts.”24 Aquinas’s thought is significant for the public sphere since “by virtue of aiming at the common good in which moral virtue is central, politics presupposes and foreshadows a human telos more common than any particular regime can provide for or reflect and which should serve as the North Star for the compass of political theory.”25

Third, natural law has been described as the “soil from which civil law ought to grow,” affording legitimacy for political life, outside of Scripture.26 Two implications flow from this. First, natural law takes precedence over human law, overruling it when justice necessitates. For example, Aquinas identified an exception to obeying the civil law concerning property rights.27 Furthermore, Aquinas defended the prelate’s duty “not to obey” if they were commanded to commit “an act of sin contrary to … virtue.”28 Hence, human law “is not the final word,” whereas natural law is the “unchangeable anchor for civil law.”29 The second implication arising from Aquinas’s understanding is that political authorities derive their authority from natural law, not from the church. While this does not entail the church’s silence on political issues, it does reflect that natural law, not the church, provides the origin of civil law.30

Fourth, in his understanding of the relationship between natural law and the Mosaic Law, Aquinas upheld the tripartite division of the Mosaic law, understanding the Decalogue as having a “supplementing function … provid[ing] a primary set of theorems from the axioms of” natural law.31 Aquinas argued, “all the moral precepts of the [Mosaic] law belong the law of nature,” although they are evident to natural reason to varying degrees.32 For our analysis, two consequences follow. First, Aquinas identifies vices such as lying as contrary to natural law, the implication of which we return to below.33 Second, through Aquinas’s distinction between “precepts” of the “far range” and “middle range” of natural law, Helm suggests reflecting on the “middle range … such a principle might perhaps be that it is permissible to kill an enemy in the prosecution of a just war.”34

Finally, we consider natural law’s utility for public theology, acknowledging that natural law is not without its detractors.35 Some Protestants are suspicious of natural law as a Romish doctrine, believing it undermines the need for special revelation and downplays sin’s noetic effects.36 Sigmund suggests a contradiction between natural law and the message of Christ.37 However, others acknowledge that while Aquinas’s natural law theory needs some refinement, nevertheless historically it “has proven to be the most enduring and perennially relevant.”38 VanDrunen helpfully refutes the criticism that natural law undermines sola scriptura, observing that the Reformers continued to uphold natural law without confusing “God’s own natural revelation” with “paganism.”39 Furthermore, Aquinas upheld the doctrine of original sin, reflecting that “natural law can be effaced, either by wrong persuasions … or by perverse customs and corrupt habits.”40 Hence, despite its detractors, natural law is an important pillar of public theology.

2.3. Natural and Supernatural Goods

In the third pillar, Aquinas distinguished between natural and supernatural goods, while avoiding their separation. Natural (or temporal) goods derive their existence from God’s creation, and are all necessary for human life.41 They are rightly pursued by all men, overseen by the state. Supernatural goods are pursued by Christians and the church, and they have eternal value. The ultimate supernatural good is the beatific vision of God, whereby that “final and perfect happiness can consist in nothing else than the vision of the Divine Essence.”42 As Gregory and Clair comment, “for Aquinas, the natural common good achieved in political community stands apart from the supernatural, eternal good found only in God, by grace, and is partially glimpsed in the ecclesial community.”43

Aquinas’s distinction between goods enabled some demarcation regarding which institution was responsible for which “good.”44 For example, clerics were prohibited from fighting in war because they were “dedicated to the pursuit of spiritual goods by their office.”45 Aquinas “fundamentally and primarily view[ed] political life as temporal: the relationship between the goods constitutive of temporal political life and the eternal goods of ultimate human happiness form both the primary distinction and primary bridge between church and political society.”46

2.4. Virtues

In the fourth pillar, following Aristotle, Aquinas’s distinction between cardinal and theological virtues is germane. Cardinal virtues, revealed by natural law to all humanity, include prudence, justice, temperance, and courage.47 Theological virtues, revealed by supernatural revelation to Christians, are faith, hope, and charity.48 This distinction helpfully reveals the common ground and distinction between Christians and non-Christians. Furthermore, it assigns “true usefulness as well as considerable limits to natural law.”49 Additionally, and the relevance of which becomes evident below, Aquinas posited orderings within the virtue of charity.50

Aquinas believed the state should promote its citizens’ virtue.51 Consequently, some dislike Aquinas’s political theory because they believe it affords the state “truly expansive” powers.52 However, as Chaplin argues, by defining the state’s role as “promoting the common good,” Aquinas’s view was “as much restrictive as it is permissive” since many aspects of justice were beyond the state’s responsibility and “the state may only act pursuant to the common good.”53 Furthermore, human law can operate only on “outward and observable behaviour,” not “inward motions which are hidden.”54

Significantly, Aquinas shows how the “infused theological virtues of faith, hope, and love orient human beings to the eternal common good and thereby help direct their use and experience of temporal goods.”55 Consequently, “the church is the locus of virtue formation … and political society is the place where political virtue must be transformed by faith, hope, and love.”56 Aquinas’s understanding of virtue provides a framework for contemporary Christian public engagement since their work in the public square should be distinctive through their embodiment of theological virtues. Furthermore, Christian influence should optimize the potential for a flourishing political society since theological virtues bring “the natural virtues to completion insofar as they are reoriented toward the supernatural end.”57

3. Just War Theory

Having considered the four pillars of Aquinas’s public theology apposite to this article’s subject, we turn to appraise his just war theory. Evaluating Aquinas’s just war theory is necessary for two reasons. First, spying has been understood as “an act of force,” and the “moral problems of spying” can be treated as “the moral problems of war.”58 Second, intelligence agencies provide support for military operations.59 Hence Christian intelligence officers are aided by just war theory, not that it seeks to justify war, but rather it “aims to bring war under the control of justice.”60 We therefore consider three aspects of Aquinas’s just war theory: its criteria, its constraints, and the context of charity. Finally, in this section on just war, we evaluate criticisms of Aquinas’s view.

3.1. Three Aspects of Aquinas’s Just War Theory

In the first aspect of his just war theory articulating jus ad bellum, Aquinas identifies three factors, drawing heavily on Augustine.61 A first factor is the requirement for legitimate authority.62 This involves the “authority of the sovereign” who may “lawfully use the sword of war to protect the commonweal from foreign attacks” (cf. Rom 13:4). 63 Conversely, private citizens have “no business declaring war.”64 However, Aquinas makes a salient distinction that if “a private person” draws the sword by the sovereign’s authority, “he himself does not ‘draw the sword,’ but is commissioned by another to use it.”65 Aquinas understands just war as “a natural function of political authority.”66 A second factor is a “just cause … namely that those who are attacked … deserve it” on account of their wrongdoing. 67 Aquinas does not explicitly distinguish between offensive and defensive wars, but while his treatise is focussed on war’s initiation, his framework readily applies to a state’s self-defence under attack.68 A third factor is “right intention,” whereby they must “intend to promote the good and to avoid evil,” reflecting natural law.69 There is an “internal logic” to Aquinas’s order, and without all three factors, war is unjustified.70

In the second aspect of his just war theory, Aquinas’s comments on jus in bello reveal his concern for virtue in war.71 While Aquinas’s account has a dearth of rules, it is “virtue-driven.”72 Of the cardinal virtues, courage and prudence are especially vital for soldiering, with duties carried out with right intention.73 Cole describes how each of the cardinal virtues enables effective soldiering.74 Aquinas evidently esteemed proportionality, desiring war’s ultimate goal of peace.75 Consequently, those fighting should “be peaceful even while you are at war.”76 Aquinas prohibited clerics from fighting, but they could provide counsel, thereby demonstrating that Christian engagement in wars “should bring a temperance and order to the process that would be lacking without them.”77

A third aspect of Aquinas’s just war theory is the importance of charity as the context for just war. In Summa Theologica, Aquinas’s discussion of just war theory comes within his treatise on charity.78 O’Donovan observes, “from the earliest attempts to understand how armed conflict might be compatible with Christian discipleship, the church has taken its bearings from the evangelical command of love.”79 On the one hand, Miller suggests that Aquinas “derived from the virtue of charity” a “presumptive attitude” against war, partly revealed by his “stacking” of arguments in q.40 of Summa Theologica.80 On the other hand, Reichberg cogently rejects this analysis, identifying methodological problems in Miller’s reading.81 Reichberg posits that Aquinas’s decision to include war within his discussion of charity served to “demonstrate how wrongful war, along with other conflict-causing vices such as discord and schism, stands opposed to the concordia that flows from charity.”82 The inclusion of war in Aquinas’s section on charity “emphasises the differences between wars fought unjustly from those fought with honourable intentions.”83

3.2. Three Criticisms of Aquinas’s Just War Theory

Finally, we attend to three criticisms of Aquinas’ position on just war, the first of which addresses just war theory’s dependence on natural law. Hauerwas contends, “violence and coercion become conceptually intelligible from a natural law standpoint.” 84 However, rightly understood, “far from preparing society for violence … [natural law] preserves social bonds and guards basic freedoms rather than threatening them.” 85 Natural law forms the basis for transnational norms of justice and human rights.86 Biggar rightly comments that without natural law,

Nuremberg was nothing but victors’ vengeance dressed up in a fiction of ‘justice,’ and today’s high-blown rhetoric of universal human rights is just so much wind … [these positions] assume that there is a universal moral order that transcends national legal systems and applies to international relations even in the absence of positive international law.87

In a second criticism, Hauerwas argues Aquinas neglected to develop the “importance of hope” and that his “overall perspective is insufficiently eschatological.”88 However, Hauerwas fails to adequately account for the “dual ethic” that Christians live under. 89 Furthermore, natural law establishes the basis for civil government, including its restraint of sin, until the Parousia.

A third criticism concerns Aquinas’s doctrine of “double effect,” which has been described as “dubious” and beset with problems.90 This is Aquinas’s “morally significant” distinction between “intention and side-effects” in his discussion about the lawfulness of lethal self-defence.91 While this could be helpful for a soldier concerned about unintended consequences of their actions, contemporary application requires careful nuance.92

4. Deception

Following our consideration of Aquinas’s public theology and just war theory, we now move to evaluation of Aquinas’s position on deception. While Cole’s assertion that “spying is nearly synonymous with lying” is overstated given the gamut of intelligence-gathering techniques used by intelligence agencies, the question of deception is nevertheless germane to our discussion.93 Consequently we evaluate two issues in relation to Aquinas’s view on deception—namely “subterfuge in war” and lying.94

First, Aquinas allows for “concealed tactics” in just war, citing Joshua’s ambush against Ai.95 Based on Aquinas’s “novel and perhaps curious reasoning … to the problems of ambushes and fighting on feast days,” Russell suggests that when war is just, “logically it should be fought by any means and at all times.”96 Gvosdev suggests Aquinas can be used to justify “ambushes and deception.”97 However, these views misrepresent Aquinas, given his concern for virtue, “right intention,” and careful distinction between dissimulation and simulation. Consequently, contra Smith, who argues that those who use false signification to protect the innocent grow in “holiness … and justice,” false signification can be “destructive of the integrity and virtue of the agent.”98 By focusing on edge cases (such as English Christians who provided false passports to Jews in the Second World War) Smith overlooks the impact of habitual lying on a person’s character, a concern of Aquinas.

Furthermore, Aquinas considers the argument that “a lesser evil must be accepted when there is question of avoiding a greater … [and so] for someone to lie in order to save one person from murdering and another from being murdered is permissible.”99 Consequently, it could be argued that in the context of saving life, to lie is sinful, but still justifiable. However, in responding to this position, Aquinas contends,

A lie has the quality of sinfulness not merely as being something damaging to a neighbour, but as being disordered in itself. Now it is not possible to employ any unlawful wrongdoing in order to prevent injury to another or another’s failings … for this reason, then, it is unlawful for anyone to lie in order to rescue another, no matter what the peril; one may, however, prudently mask the truth.100

For Aquinas, telling a falsehood or breaking a promise with an enemy is always “unlawful,” but nevertheless a soldier, and therefore by extension a government intelligence officer, may rightly disguise his intentions from an enemy.101 While subterfuge and concealment are permitted, lying is prohibited.

Second, Aquinas’s position on lying is rooted in natural law, allowing no exceptions. Lying is “inherently evil,” “contrary to [human] nature.”102 Strikingly, Aquinas does not directly connect prohibitions on lying to God’s character, unlike some contemporary arguments made against lying in all circumstances.103 However, since the Decalogue is ordered to the love of God, revealing natural law, “false witness against a neighbour is explicitly forbidden.”104 While Aquinas permits exceptions to some other laws, such as private property, lying differs since it is rooted in natural law, not civil law.105

Two potential critiques emerge. First, Aquinas’s view of natural law does not appear to anticipate conflicts between two or more natural laws.106 For example, in extreme cases such as the frequently cited example of a member of the Gestapo knocking on the door and asking if any Jews are inside, the desire “for good to be done and evil avoid[ed]” appears at odds with universal natural law prohibitions on lying.107

Second, Aquinas’s exposition of passages describing the lying of people commended in scripture as “figurative,” “prophetic,” or “mystical” is unpersuasive.108 Furthermore, while Aquinas’s interpretation is closely mirrored in both Augustine and Calvin’s thought, others such as Chrysostom and Luther believed it permissible to lie in order to save innocent life, highlighting the complexities and potential nuance.109 If one accepts the Decalogue as reflecting natural law, the crux lies in interpretation of the ninth commandment, specifically how one conceives of the “neighbours” against whom false witness is forbidden (Exod 20:16).

5. Conclusion: Should Christians Work for Intelligence Agencies?

Finally, having surveyed the application of Aquinas’s theology to just war theory and deception, we conclude with seven ways in which Aquinas illuminates and shapes the grounds on which Christians might work in intelligence agencies, informing how a church might pastor those engaged in such work.

First, Aquinas provides a cogent basis for Christian engagement in the public square. By upholding the distinction between private citizens and individuals working for public authorities, there are some actions, such as wielding the sword, that Christians are permitted to do in a public capacity in particular circumstances, which would otherwise be prohibited for them as private citizens. This understanding encompasses, notwithstanding the qualifications discussed below, Christians working in intelligence. Furthermore, Aquinas’s distinction between supernatural and natural goods reveals how Christians should engage positively with temporal activities, such as pursuit of safety.

Second, intelligence agencies seek to advance and defend the national interest. In his treatise on charity, Aquinas identifies orderings, including “morally obligatory self-love” as a legitimate category.110 Biggar argues that since Aquinas recognizes the human individual’s “duty to care for himself properly … seek[ing] what is genuinely his own good,” the same applies for national communities, and their government.111 Consequently, working in the national interest is a legitimate activity for the Christian.

Third, the derivation of civil law from natural law meant that Aquinas upheld civil law to the extent that it pertained to the common good. Consequently, Aquinas would counsel that Christians disobey unjust human laws, for example, in Nazi Germany. For the Christian intelligence officer, this highlights the insufficiency of relying solely on legality as the basis for their work, illuminating the need for a broader ethical framework since what is legal is not always ethical.

Fourth, Aquinas’s articulation of theological and cardinal virtues shows how a Christian’s heart-attitude should be transformed by faith, hope, and love. Aquinas’s concern for theological virtue illuminates a danger for those in occupations where dealing with the necessary restraint of sin can easily lead to hard-heartedness and gallows humor. Christians in such roles must actively cultivate tender consciences.

Fifth, this distinction between virtues also reveals how Christians exert a positive witness and influence at work. The Christian’s embodiment of theological virtues should transform the ways they speak and pray for their “targets.”112 In addition, the Christian’s exercise of theological virtue shapes their application of cardinal virtues, enabling virtuous decision-making in the political sphere, for the common good.

Sixth, Aquinas’s emphasis on just causes and evaluation of unintended consequences suggests he would affirm the desire for necessity and proportionality expressed in recent UK legislation pertaining to intelligence activity.113 For example, Aquinas supported domestic rebellion against tyranny only if it was likely to result in greater benefit to the public good.114

Seventh, Gvosdev suggests that Aquinas can be used to justify espionage.115 However, if Christians accepted Aquinas’s position on lying, they would need to absent themselves from some aspects of intelligence work. Even if one adopted the view, contra Aquinas, that some lying is permissible in a just cause, the Christian would need to carefully consider the scope of permissible lying and the impact on their character, especially in a private capacity. In the context of a local church where a significant number of its members are engaged in the intelligence services, this would be an important subject to explore further.

To conclude, imagine that several members of your church are engaged in intelligence work, whether you know it or not. Should the church’s position towards their profession be one of live and let spy? In our brief excursus into the theology of Thomas Aquinas, it is evident that his framework affords considerable help in evaluating the appropriateness of Christian engagement in intelligence work, upholding and qualifying their participation. Aquinas’s perspective offers several important ways that churches can effectively pastor Christian intelligence officers as they navigate the particular complexities of their work for the Lord.

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[1] As Alec Leamas declared in the John Le Carre film, The Spy Who Came in from the Cold, cited in Darrell Cole, “Whether Spies Too Can Be Saved,” JRE 36 (2008): 126.

[2] For example, in the UK, by government intelligence agencies we refer to GCHQ, MI5, and MI6.

[3] Peter Orr, “Two Types of Work: Work for the Lord and Work for the Kingdom of God,” Themelios 47 (2022): 70–80.

[4] David VanDrunen, Natural Law and the Two Kingdoms: A Study in the Development of Reformed Social Thought (Grand Rapids: Eerdmans, 2010), 43; Frederick H. Russell, The Just War in the Middle Ages (Cambridge: Cambridge University Press, 1975), 289.

[5] John Ferris, Behind the Enigma: The Authorised History of GCHQ, Britain´s Secret Cyber-Intelligence Agency (London: Bloomsbury Publishing, 2021), 689.

[6] Thomas Aquinas, Summa Theologica, trans. Fathers of the English Dominican Province, 60 vols. (London: Eyre and Spottiswoode, 1966), II–II q.40. For further discussion of this piecemeal methodological approach, see Daniel H. Weiss, “Aquinas’s Opposition to Killing the Innocent and Its Distinctiveness within the Christian Just War Tradition,” JRE 45 (2017): 482.

[7] For an overview of his thought on a broader range of questions, see Eleonore Stump, Aquinas (London: Routledge, 2003).

[8] Eric Gregory and Joseph Clair, “Augustinianisms and Thomisms,” in The Cambridge Companion to Political Theology, ed. Craig Hovey and Elizabeth Phillips (Cambridge: Cambridge University Press, 2015), 186.

[9] Aquinas draws on Aristotle who described man as a “political animal” (zoon politikon). See Thomas Aquinas, “On Kingship or the Governance of Rulers (De Regimine Principum, 1265–1267),” in St. Thomas Aquinas on Politics and Ethics: A New Translation, Backgrounds, Interpretations, trans. and ed. Paul E. Sigmund, Norton Critical Edition (New York: Norton, 1988), 14.

[10] Gregory and Clair, “Augustinianisms and Thomisms,” 176.

[11] Gregory and Clair argue for a “revision of the standard interpretative pictures,” bringing “Augustine and Aquinas closer together.” O’Donovan speaks of the convergence of their views, evident in comments on political life made by Luther and Vitoria, from the Augustinian and Thomist positions respectively. Gregory and Clair, “Augustinianisms and Thomisms,” 177; Oliver O’Donovan, The Ways of Judgment: The Bampton Lectures, 2003 (Grand Rapids: Eerdmans, 2005), 60.

[12] A full exploration of Aquinas’s understanding of this relationship in his context is beyond our scope. However, we observe the complexities. For example, in De Regno, while Aquinas argues that “spiritual and earthly things may be kept distinct” in distinguishing between the responsibilities of “secular and spiritual powers,” he also affirms papal supremacy over earthly rulers. While Sigmund identifies a contradiction, Weisheipl suggests that Aquinas is asserting the church’s “moral authority,” not its “legal right to intervene.” See Aquinas, “On Kingship,” 27, 28 n. 3; Paul E. Sigmund, “Law and Politics,” in The Cambridge Companion to Aquinas, ed. Norman Kretzmann and Eleonore Stump (Cambridge: Cambridge University Press, 1995), 218–19.

[13] Aquinas, “On Kingship,” 28–29; Aquinas, Summa Theologica II–II q.40 a.1, resp.

[14] Aquinas, Summa Theologica I–II q.90 a.4, resp.

[15] Aquinas, Summa Theologica I–II q.91 a.1, resp.

[16] Aquinas, Summa Theologica I–II q.91 a.2, resp.

[17] Aquinas, Summa Theologica I–II q.91 a.3, resp.

[18] Norman L. Geisler, Thomas Aquinas: An Evangelical Appraisal (Grand Rapids: Baker Books, 1991), 166.

[19] Thomas Aquinas, Summa Contra Gentiles, trans. Vernon J. Bourke, 4 vols. in 5 parts (London: University of Notre Dame Press, 1975), 3:115.

[20] Matthew Levering, Biblical Natural Law: A Theocentric and Teleological Approach (Oxford: Oxford University Press, 2008), 194.

[21] David VanDrunen, Politics after Christendom: Political Theology in a Fractured World (Grand Rapids: Zondervan, 2020), 134–35.

[22] VanDrunen, Politics after Christendom, 135; Aquinas, Summa Theologica I–II q.94 a.2, resp.

[23] Aquinas, Summa Theologica I–II q. 91 a.2, sed c. The question of whether Romans 2:14–15 pertains to unbelieving gentiles or gentile Christian obedience is often contested. According to the former view, Paul is describing natural law in these verses. For a recent and detailed discussion of these two interpretative positions, see Thomas R. Schreiner, Romans, 2nd ed., BECNT 6 (Grand Rapids: Baker Books, 2018), 128–33.

[24] Geisler, Thomas Aquinas, 165.

[25] Mary M. Keys, “Politics Pointing beyond the Polis and the Politeia: Aquinas on Natural Law and the Common Good,” in Natural Moral Law in Contemporary Society, ed. Holger Zaborowski (Washington: Catholic University of America Press, 2010), 185.

[26] David VanDrunen, Divine Covenants and Moral Order: A Biblical Theology of Natural Law (Grand Rapids: Eerdmans, 2014), 26.

[27] Aquinas, Summa Theologica II–II q.66 a.7, sed c.

[28] Thomas Aquinas, Commentary on the Sentences II, trans. Roberto Busa. (Parma Edition, 1858), div. 44 q. 2 a.2, resp. https://aquinas.cc/la/en/~Sent.II.D44.Q2.A2.C.

[29] Nigel Biggar, In Defence of War (Oxford: Oxford University Press, 2013), 214–15; Geisler, Thomas Aquinas, 174.

[30] Thomas Gilby, “Appendix 1: Law and Dominion in Theology (1a2ae. 90, 1-4),” in Summa Theologica vol. 28, 60 vols. (London: Eyre and Spottiswoode, 1966), 161. Although as noted above (n. 12), Aquinas’s view allowed for papal intervention in the political sphere.

[31] Paul Helm, “Calvin and Natural Law,” SBET 2 (1984): 11.

[32] Aquinas makes a distinction: “the moral character of some human actions is so evident that they can be assessed as good or bad in light of these common principles [the moral precepts] …with a minimum of reflection.” However, others “need a great deal of consideration … [by] those endowed with wisdom.” He also recognizes another “class of actions, which require for their assessment the aid of divine instruction, such as those which belong to the province of faith.” Aquinas, Summa Theologica I–II q.100 a.1, sed c; resp.

[33] Aquinas, Summa Theologica II–II q.110 a.1, resp.

[34] Helm, “Calvin and Natural Law,” 11.

[35] Grabill identifies several reasons for natural law’s fall from favor in “twentieth-century Protestant theological ethics,” “not least of which can be attributed to Karl Barth’s epistemological criticism of natural theology.” Stephen John Grabill, Rediscovering the Natural Law in Reformed Theological Ethics (Grand Rapids: Eerdmans, 2006), 52.

[36] For an overview, see C. Ben Mitchell, Ethics and Moral Reasoning: A Student’s Guide, Reclaiming the Christian Intellectual Tradition (Wheaton, IL: Crossway, 2013), 63–64. For pointed criticism, see Cornelius Van Til, The Defense of the Faith, ed. K. Scott Oliphint, 4th ed. (Phillipsburg, NJ: P&R Publishing, 2008), 56–57, 69–78.

[37] Sigmund identifies, “Protestant Christians are critical of … [Aquinas’s] refusal to recognise that there are contradictions between a rationalistic teleological natural law theory and certain aspects of the message of Christ, such as sacrificial love, martyrdom, rejection of wealth and worldly possessions, and ‘turning the other cheek.’” Sigmund, “Law and Politics,” 229.

[38] VanDrunen identifies six continuities and two discontinuities between his understanding of natural law and Aquinas’s view. VanDrunen argues that two areas where Aquinas’s thought needs reform are (1) the “larger metaphysics in which Thomas’s understanding of natural law is embedded” and (2) “the famous Thomistic formula that grace does not destroy nature but perfects it.” VanDrunen, Divine Covenants and Moral Order, 22–36.

[39] VanDrunen, Divine Covenants and Moral Order, 488–89.

[40] Aquinas cites robbery as an example of a vice that is not held as wrong by some people, due to the effacement of natural law in their hearts. Aquinas, Summa Theologica I–II q.94 a.6, resp.

[41] Aquinas, Summa Theologica I–II q.94 a.2, resp.

[42] Aquinas, Summa Theologica I–II q.3 a.8, resp.

[43] Gregory and Clair, “Augustinianisms and Thomisms,” 178–79.

[44] Gregory and Clair, “Augustinianisms and Thomisms,” 179.

[45] Russell, The Just War in the Middle Ages, 282. Aquinas, Summa Theologica II–II q.40 a.2, resp., ad 3.

[46] Gregory and Clair, “Augustinianisms and Thomisms,” 178.

[47] Aquinas, Summa Theologica I–II q.61.

[48] Aquinas, Summa Theologica I–II q.62.

[49] VanDrunen discusses how Aquinas’s “nature-grace structure” through its distinction of theological and cardinal virtues shows both the utility and limits of what can be known through natural law. VanDrunen, Natural Law and the Two Kingdoms, 106.

[50] Aquinas, Summa Theologica II–II q.26.

[51] Jones comments that Aquinas’s understanding of human law must be understood by reading both Summa Theologica and De Regno since the latter offers a fuller account of his position. In De Regno, Aquinas “is quite emphatic that the common good of society is not merely limited to establishing a condition of civic tranquility and unity among people … genuine virtue is the proper aim of any ruler.” Brian Jones, “‘Securing the Rational Foundations of Human Living’: The Pedagogical Nature of Human Law in St. Thomas Aquinas,” New Blackfriars 96: 613.

[52] For a response to suggestions that Aquinas was pushing for “truly expansive” powers, see Jonathan Chaplin, “‘Justice,’ the ‘Common Good,’ and the Scope of State Authority: Pointers to Protestant-Thomist Convergence,” in Aquinas among the Protestants, ed. Manfred Svensson and David VanDrunen (Hoboken: Wiley, 2017), 288–89, 293.

[53] Chaplin, “‘Justice,’ the ‘Common Good,’ and the Scope of State Authority,” 291–93.

[54] Aquinas, Summa Theologica I–II q.91 a.4, resp. 3.

[55] Gregory and Clair, “Augustinianisms and Thomisms,” 190.

[56] Gregory and Clair, “Augustinianisms and Thomisms,” 192.

[57] Darrell Cole, “Thomas Aquinas on Virtuous Warfare,” JRE 27 (1999): 76.

[58] Cole, “Thomas Aquinas on Virtuous Warfare,” 126–27.

[59] Ferris comments on the role of signals intelligence (SIGINT) in counter-surgency operations in Iraq and Afghanistan: “Siginters [analysts working on signals intelligence] became more entangled in battle than ever before. The decline in service Siginters and the rise of military precision strikes threw civilian officials into kill chains … GCHQ no longer was just an intelligence organisation, but part of executive agencies for the use of force.” Ferris, Behind the Enigma, 694–95.

[60] Arthur F. Holmes, “The Just War,” in War: Four Christian Views, ed. Robert G. Clouse (Downers Grove, IL: IVP, 1981), 119.

[61] Jus ad bellum refers to the factors governing a “decision to deploy” the use of armed force. In his treatment of just war in q.40 Aquinas repeatedly cites Augustine to advance his position. Russell comments on how Aquinas “fused the Aristotelian political theory to the traditional Augustinian outlook of his predecessors.” Howard M. Hensel, “Christian Belief and Western Just War Thought,” in The Prism of Just War: Asian and Western Perspectives on the Legitimate Use of Military Force, ed. Howard M. Hensel, Justice, international law, and global security (Farnham: Ashgate, 2010), 42–54; Aquinas, Summa Theologica II–II q. 40; Russell, The Just War in the Middle Ages, 258.

[62] Aquinas, Summa Theologica II–II q.40 a.1, resp. 1

[63] Aquinas, Summa Theologica II–II q.40 a.1, resp. 1

[64] Aquinas, Summa Theologica II–II q.40 a.1, resp. 1.

[65] Aquinas, Summa Theologica II–II q.40 a.1, resp. ad. 1.

[66] Russell, The Just War in the Middle Ages, 280–81.

[67] Aquinas, Summa Theologica II–II q.40 a.1, resp. 2.

[68] John Finnis, Aquinas: Moral, Political, and Legal Theory (Oxford: Oxford University Press, 1998), 285.

[69] Aquinas, Summa Theologica II–II q.40 a.1, resp. 1.

[70] Biggar, In Defence of War, 251.

[71] Jus in bello refers to the constraints on the application of war. Hensel, “Christian Belief and Western Just War Thought,” 54–60.

[72] Cole, “Thomas Aquinas on Virtuous Warfare,” 58, 78.

[73] Hensel, “Christian Belief and Western Just War Thought,” 55.

[74] For example, prudence enables cogent military decision-making. Justice “enables us to distinguish just wars and unjust wars.” Courage is essential for soldiering. Temperance “is the virtue that can check actions born from hate and revenge.” Cole, “Thomas Aquinas on Virtuous Warfare,” 62–63.

[75] Hensel, “Christian Belief and Western Just War Thought,” 58; Aquinas, Summa Theologica II–II q.40 a.1, resp. ad. 3.

[76] In his discussion on war, this is another instance where Aquinas directly quotes Augustine. Aquinas, Summa Theologica II–II q.40 a.1, resp. ad. 3.

[77] Cole, “Thomas Aquinas on Virtuous Warfare,” 76. The reason for Aquinas’s prohibition on clerics is not because of their Christian faith, but because of their calling as Christian ministers. Aquinas, Summa Theologica II–II q.40 a.2, resp. ad. 2.

[78] Aquinas, Summa Theologica II–II q.34-46.

[79] Oliver O’Donovan, The Just War Revisited, Current Issues in Theology 2 (Cambridge: Cambridge University Press, 2003), 9.

[80] Commenting on Aquinas’s opening question in q.40 (“is it always a sin to wage war?”), Miller suggests, “by starting with the idea that war might be sinful, Aquinas seems to establish a burden of proof in favour of nonviolence and against war.” Richard B. Miller, “Aquinas and the Presumption against Killing and War,” JR 82, (2002): 181, 193, 202. Aquinas, Summa Theologica II–II q.40 a.1.

[81] Gregory M. Reichberg, “Thomas Aquinas between Just War and Pacifism,” JRE 38, (2010): 219–41.

[82] Reichberg, “Thomas Aquinas between Just War and Pacifism,” 224.

[83] Pemberton evaluates the debate between Miller and Reichberg, agreeing with Reichberg while adding further reasons to reject Miller’s analysis. Lloyd George Pemberton, “Aquinas the Pacifist? A Comparative Study” (MA thesis, Liberty University Graduate School, 2015), 34.

[84] Stanley Hauerwas, The Peaceable Kingdom: A Primer in Christian Ethics. (London: SCM, 2003), 61.

[85] J. Daryl Charles, Retrieving the Natural Law: A Return to Moral First Things (Grand Rapids: Eerdmans, 2008), 145.

[86] Biggar, In Defence of War, 214.

[87] Biggar, In Defence of War, 214.

[88] Hauerwas, The Peaceable Kingdom, 159.

[89] In his account of natural law, VanDrunen highlights the law of love, the Decalogue and the Noahic covenant as reflecting natural law. The “minimalistic natural law ethic” of Gen 9:1–7, includes the “enforcement of retributive justice.” Consequently, VanDrunen persuasively suggests that “the error of the nonviolent perspective … is that it fails to reckon with the dual covenants under which Christians live and hence the dual character of their ethics … the church … is to embody the peaceable ways of the kingdom, but this does not deprive the state of its legitimacy … the legitimate use of the sword in defense of justice ends not with Jesus’ first coming, but at his second coming.” VanDrunen, Divine Covenants and Moral Order, 497–501.

[90] O’Donovan, The Ways of Judgment, 209–10; Biggar, In Defence of War, 106–10.

[91] Finnis, Aquinas, 276. Aquinas, Summa Theologica II–II q.64 a.7, resp.

[92] Full discussion of this doctrine is beyond our scope, although we note the use of this doctrine to defend nuclear deterrence. Sigmund, “Law and Politics,” 228. For an argument that rejects the utility of double effect, see Alison McIntyre, “Doing Away with Double Effect,” Ethics 111 (2001): 219–55.

[93] Cole, “Whether Spies Too Can Be Saved,” 133. Cole’s assertion is shown to be an overstatement by observing the range of techniques used for gathering intelligence, as described on MI5’s website, suggesting that deception is not intrinsic to all of them, see MI5, “Gathering Intelligence,” https://www.mi5.gov.uk/gathering-intelligence. However, the importance of deception is revealed in the description of “intelligence officers … who may operate under non-official cover to conceal the fact that they work for an intelligence service—posing as a business person, student or journalist for example. In some cases, they may operate in ‘deep cover’ under false names and nationalities.” See MI5, “How Spies Operate,” https://www.mi5.gov.uk/how-spies-operate.

[94] Aquinas, Summa Theologica II–II q.40 a.3; q.110.

[95] Josh 8:2, 14. Aquinas, Summa Theologica II–II q.40 a.3 sed c.

[96] Russell, The Just War in the Middle Ages, 272.

[97] Although the quotation from Aquinas that Gvosdev cites in his paper distinguishes between ambushes and deceptions, Gvosdev’s analysis fails to adequately capture this nuance. Nikolas K. Gvosdev, “Espionage and the Ecclesia,” JCS 42 (2000): 817 [my italics].

[98] Janet E. Smith, “Fig Leaves and Falsehoods: Disagreeing with Thomas Aquinas,” First Things, June 2011, 48, https://www.firstthings.com/article/2011/06/fig-leaves-and-falsehoods.

[99] Aquinas, Summa Theologica II–II q.110 a.3, ad. 4.

[100] Aquinas, Summa Theologica II–II, q.110 a.3, resp. ad. 4.

[101] Aquinas comments, “all the more then should we hide from the enemy our plans against him … now this sort of concealment is the idea behind the subterfuge one may lawfully use in just wars.” Aquinas, Summa Theologica II–II q.40 a.3, resp.

[102] Aquinas, Summa Theologica II–II, q.110 a.3. resp.

[103] For an example of a contemporary position on lying that directly makes this move, see Grudem, who argues that God’s unchanging character as the one “who never lies” (Titus 1:2) is the grounds for ethical norms against lying. Christians should be progressively conformed to God’s image, not that of Satan (John 8:44). Aquinas, Summa Theologica II–II q.110; Wayne Grudem, “Why It Is Never Right to Lie: An Example of John Frame’s Influence on My Approach to Ethics,” in Speaking the Truth in Love, ed. John J. Hughes (Phillipsburg: P&R Publishing, 2009), 788–89.

[104] Aquinas, Summa Theologica II–II q.110 a.4, resp. ad. 2.

[105] Aquinas, Summa Theologica II–II q.66 a.7, sed c.

[106] Geisler, Thomas Aquinas, 169, n. 36.

[107] Cole, “Whether Spies Too Can Be Saved,” 138.

[108] For example, “Jacob’s assertion that he was Esau, Isaac’s firstborn, has a mystical sense, namely that Esau’s birthright was his by right.” Aquinas, Summa Theologica II–II q.110 a.3, resp. ad. 3.

[109] Cole compares the thinking of Augustine, Aquinas, and Calvin about lying with Luther and some of the Eastern Christian Fathers. Cole, “Whether Spies Too Can Be Saved,” 133–36.

[110] Aquinas, Summa Theologica II–II q.26. Biggar, In Defence of War, 231.

[111] Biggar argues that a “national government has a moral duty to look after the well-being of its own people—and in that sense to advance its genuine interests.” Biggar, In Defence of War, 231.

[112] For an example of the language of “target[s] of an investigation,” see MI5, “Gathering Intelligence,” https://www.mi5.gov.uk/gathering-intelligence.

[113] For an example of the emphasis on necessity and proportionality, see HMG, “Explanatory Notes: Investigatory Powers Act 2016”; https://www.legislation.gov.uk/ukpga/2016/25/pdfs/ukpgaen_20160025_en.pdf.

[114] Aquinas argued, “disturbing such a [tyrannical] government has not the nature of sedition, unless perhaps the disturbance be so excessive that the people suffer more from it than from the tyrannical regime.” Aquinas, Summa Theologica II–II q.42 a.2, resp. ad. 3.

[115] Gvosdev, “Espionage and the Ecclesia,” 817.