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date: 22 April 2018

Ethics, Justice, and Security

Summary and Keywords

The concepts of ethics, justice, and security are inextricably linked within the field of International Relations (IR). In IR, three concepts are most often deployed in understanding the ethics of security: norms, rules, and laws. These norms, rules, and laws evaluate security, which is an alternative concept for describing what IR as a discipline has long sought to address: namely, war. Hence, norms, rules, and laws provide a means to evaluate violence and war. Using the first three concepts to evaluate the latter two is the heart of ethics and security. The concept of justice, however, suggests that simple norms, rules, and laws may not be enough. There have been debates about the use of military force since ancient times—the Judeo-Christian, Greco-Roman, and Islamic traditions have their own conceptions of how war and violence ought to be addressed. One of the more prominent ideas drawn from these debates is the concept of the “just war,” which emerged from Christian tradition. The concept of just war has played a role in constructing the international legal tradition. This tradition as an explicit moral one was subsumed into international law during the nineteenth century, but re-emerged in the mid-twentieth century. Today, it has become an influential source of critical reflection upon both legal and practical dilemmas in international security, informing a wide range of debates around the world.

Keywords: ethics, justice, security, international security, just war, violence, religious traditions, moral traditions, military force


Moral evaluations of violence and warfare are not new; every religious, cultural, and political system has included norms, rules, and laws related to the use of force. Understanding the relationship between ethics, justice and security, then, requires a review of not only recent literature in the field of International Relations (IR), but more traditional sources. Drawing upon this wider range of sources, I argue in this essay that the ethics of security must be understood in the context of political authority, both domestic and international. The concept of justice provides the link between ethics and political authority. How such a wide array of concepts link together will be explored through a review of both ancient and modern works on military force.

Conceptual Clarifications

Norms, Rules, and Laws

In IR, three concepts are most often deployed in understanding the ethics of security: norms, rules, and laws. A norm is a “shared expectation for the proper behaviour of agents with a particular identity” (Katzenstein 1996:5). Norms are background conditions that structure the way individuals see the world around them and their role within that world. The work in IR that focuses on norms is best understood as a mode of descriptive ethics (see Harbour (1999) for descriptive versus other modes of ethical inquiry in international affairs). A number of analysts have sought to determine not only what norms play a role in international security structures, but how those norms evolve and change through interactions and changes in the international political order (Katzenstein 1996; Adler and Barnett 1998; Thomas 2001; Finnemore 2003).

Norms sometimes become rules, although the concept of a rule differs in important ways from a norm; rules have more of an explicitly binding force than norms. This may not always be the case, for customary rules emerge over time that may not have come from a single source; such rules, however, tend to take on a more authoritative structure as they persist through time (Onuf 1989; Kratochwil 1989; Lang et al. 2006; Fierke 2007; Lang and Beattie 2008).

The last type of ethical injunction that structures international security is law. Laws can be understood as rules that arise from an authoritative system and that have a force of sanction behind them (Kelsen 1966; Hart 1994). There is an immense amount of literature on the laws governing international security, which this chapter does not address in any depth. A few authors have more explicitly linked law to traditions of ethics (Johnson 2004) and some have looked to the historical development of international law to find its normative sources (Koskenniemi 2002). More importantly, while the law of armed conflict has progressively moved away from its direct relationship with ethical traditions, there remain references to certain kinds of norms in some of the most famous international legal texts. Perhaps the most well known is the Martens Clause found in the introductory sections of the Hague Conventions; the clause notes that when the codes listed do not apply to a specific situation, individuals are under the protection of the “laws of humanity and the dictates of the public conscience” (reprinted in Roberts and Guelff 2003:70).

Violence, War, and Security

What do these norms, rules, and laws evaluate? Security, the subject of this volume, is an alternative concept for describing what IR as a discipline has long sought to address, namely war. International security, however, has expanded the ambit of what is necessary to consider beyond the tradition of interstate war. One way to link the study of ethics with this wider range of issues is through an even more basic concept – violence.

Violence is the exertion of force by people so as to injure or abuse other people. In the modern world, most ethical frameworks propose that violence is wrong and should be limited if at all possible; the extreme form of this point would be pacifism. Violence on its own is not necessarily political, for it can be between two individuals or within an apolitical context (e.g., a family). War is the traditional way in which violence has appeared in the international realm. War can be defined as the use of violence by one political community in its relations with another political community. As a result, war makes violence political. Some, most famously Clausewitz, abstract war so that it is primarily about coercion between political communities, but that coercion ultimately falls back upon the threat and use of violence (Clausewitz 1968; see Pierce 2003).

International security has expanded this traditional understanding of violence at the international level into new areas. Security, unlike war or even violence, does not refer to a specific action, but is better understood as a particular state of affairs. The meaning of security has been further expanded by those in IR who have developed the idea of critical security studies (Krause and Williams 1997; Wyn Jones 1999; Booth 2004). This body of literature explores how social, economic, and environmental structures can create violence and threaten the welfare of individuals and communities.

It is not clear how traditional ethical modes can speak to the issue of critical security (see Bain 2006 for one attempt). As noted above, because most ethical formulations focus on norms, rules, and laws, these injunctions specify what individuals and groups can and cannot do in their relation with others. But if, say, global warming is considered to be a security threat, how do the specific ethical modes designed to deal with war speak to this new threat? Of course, ethics speaks to environmental issues; the question is, rather, how do ethical formulations designed to deal with collective violence actually speak to the kinds of threats that are being identified in the critical security literature? There has yet to be a real engagement with this question, which leaves open an important area of research in IR and ethical philosophy more generally. As a result, this chapter will focus primarily on the ethics of war and military force rather than the wider array of issues now considered under the rubric of international security.

Finally, there are those whose writings on security within IR have explored the normative dimension. Although realism is often seen to have nothing to say about ethics, a recent resurgence in literature within the realist tradition has emphasized the centrality of norms and rules. Specifically, “classical realists” such as Hans Morgenthau have become known for their writings on ethics as much as for their work on the importance of power (Morgenthau 1986; Williams 2007).


Norms, rules, and laws give us a means to evaluate violence and war. Using the first three concepts to evaluate the latter two is really the heart of ethics and security. The middle term in the essay title – justice – suggests that simple norms, rules, and laws may not be enough. According to the ancients, justice was one of the four cardinal virtues, the virtue of holding the others and the self in balance. Justice is ultimately about fairness, or the fair distribution of a good – in this case, peace or security. That distribution is intimately linked with authority and legitimacy. Central to justice is thus an understanding of the political community, its standards, structures, and processes.

The political context is important in two separate ways when it comes to the ethics of security. The first is that specific contexts, with cultural and political codes and processes, produce the ethics that are the subject of this chapter. One cannot understand a specific ethical injunction without understanding its origins in a particular place. This point is difficult to square with international norms, rules, and laws, for it is assumed that such ethical injunctions are not grounded in any particular place but reflect a kind of shared humanity. The international system may well be moving in this direction (Sullivan and Kymlicka 2007), but those movements generally start from some particular place with a particular tradition.

The second dimension of the political context that is important to emphasize is the role of authority. If it is the case that the cultural and broader national context determines ethical codes, the role of an authority structure to interpret those codes in specific situations is also central. This is not a Hobbesian point that the sovereign determines what is right and wrong; rather, it is that decisions to use force generally come from a legitimate authority structure. Indeed, to convince people to sacrifice their lives or to kill others requires more than a simple wish on the part of an individual. Instead, it requires the acceptance by individuals that the use of force not only corresponds to a set of norms but is authorized by a legitimate structure. As a result, in all the traditions explored below, authority is a central consideration. The just war tradition has formalized the centrality of authority for decisions to use force, although research on what constitutes just authority has waned in recent years. As competing authority structures (e.g., states, United Nations, NATO, European Union) play more important roles in the governance of international security, questions on authority will become more and more central to scholarship in this field.

Religious Traditions

Judeo-Christian Tradition

Biblical Norms

The most well-known and obvious starting point in the Judeo-Christian scriptures for reflection on war is the sixth commandment: You shall not murder (Exodus 20:13). There is some disagreement amongst biblical scholars on this translation, for the Hebrew root does not convey exactly the distinction between murder and killing. Moreover, in other contexts in the Bible, the same root word is used to refer to unintentional killing (Deuteronomy 4:41ff. and Joshua 20:3). Whatever the translation, though, this rule was not absolute, as is reflected in the record of war and violence found throughout the historical books of the Bible.

Rather than appeal to a simple rule, to capture the complexity of the biblical tradition, one needs to consider some of the norms that can be found within it. One is the idea of herem, which has sometimes been translated as the “ban.” This concept refers to those things that are to be sacrificed to God after a war – including the enemy population (Numbers 31:1–54). Such norms may have made sense in a particular type of community, but as the ancient Israelite community evolved, and as its authority structures changed, the ethics governing war also evolved. For instance, during a period when the Israelites are trying to establish their dominance in the region of Canaan, killing through deception and trickery become more common. Stories from Judges demonstrate these new norms, especially those concerning Ehud (Judges 3:15–25) and Jael (Judges:17–22). The context in which such actions took place, however, was one in which there were competing authority structures; the book famously ends with the lamentation that “In those days, there was no king; all the people did what was right in their own eyes” (Judges 21:25). In comparison to the next stage in Israelite history, when the kingdoms of Saul, David, and their successors created a more formalized set of norms governing warfare, the time of the Judges created more space for uses of violence that were less rule-governed.

The arrival of Jesus of Nazareth produces a new tradition, that of Christianity. The stories of Jesus, found in the Gospels, describe an individual who refused the normal modes of political authority, including the use of violence. The Gospel of Luke provides some of the clearest expressions of this resistance to using force, captured in passages such as that of calling his followers to love their enemies (Luke 6:27–36) and his refusal to allow his disciples to protect him with violence as he is arrested (Luke 23:50–3). Yet, other biblical passages suggest Jesus did not renounce violence completely, as when he deals with Roman soldiers without chastising them for their profession (Luke 7:1–10). These conflicting accounts within the Christian Bible have generated a great deal of debate about Jesus’ views on war and peace (Ford 1984; Hauerwas 1985; Yoder 1994; Koontz 1996).

The Evolution of Judaism and Christianity

The biblical sources are not the end point of debate about the use of military force in the Jewish and Christian traditions. The rich writings of the Jewish legal tradition and rabbinical commentary demonstrate how Jewish views on violence and war evolved through the centuries. In a community largely without a territorial identity (after being expelled from Palestine in the early first century), the rabbis took the texts of the Bible and developed a complex set of justifications for war and violence. Because of this lack of a territorially defined identity, Michael Walzer points out, “Jews are the victims, not the agents, of war” (Walzer 1996:96). The development of Jewish thought in the medieval period has been the subject of recent reformulations, some of it focusing on philosophers such as Maimonides (Ravitzky 1996; Feldman 2005).

With the creation of an authoritative structure within which Jewish thought and practice about war could develop, i.e. the state of Israel, ethical reflection on security developed further. The state of Israel is not formally Jewish, but norms, rules, and laws concerning warfare draw upon a mixture of Zionist political thought and Jewish reflections on war. As a result of the regional political context in which Israelis have found themselves, their reflections on war and peace have addressed some of the issues of importance to the larger international community today, such as pre-emptive versus preventive war (Bleich 1983) and counterterrorism policy (Rosen 2003). Other theorists have sought to contribute more broadly to international ethics on questions of war and peace from a Jewish perspective (Gopin 2002; Solomon 2006). For a living religious tradition that is responding to the political situation of a particular state, these reflections will most certainly continue (see Walzer et al. 2003; 2006).

The Christian tradition also evolved from its biblical roots. The early Christian Church largely adopted a pacifist approach, but this position was linked to the refusal to serve in the Roman Empire (Bainton 1961). When Constantine made Christianity the official religion of the Empire in the mid-fourth century, Christianity moved away from its pacifist origins. The most important figure here was Augustine of Hippo (ad 354–430) who served as a bishop in North Africa (Brown 1969). There does not exist in Augustine’s corpus a single text on war and peace; rather, his ideas are spread throughout his writings, sermons and letters. His attitude toward war is that it is necessary for the creation of an acceptable order on earth, but this earthly order can never match the heavenly order, which is where the only true justice is to be found. Even more importantly, he sees war as an evil that must never be embraced but should be undertaken reluctantly, so that mercy and justice discipline war.

Unlike modern notions of security and war, Augustine’s theory does not emphasize self-defense as the primary justification for war. Because he sees war as something that an authority should use to create a particular kind of order, he argues that punishment is the most just reason to use war: “Just wars are defined as those which avenge injuries, if some nation or state against whom one is waging war has neglected to punish a wrong committed by its citizens” (from Questions on the Heptateuch, Book VI, Chapter 10, reprinted in Reichberg et al. 2006:82).

Connected to the importance of punishment, in Book 19 of the City of God, he argues that peace should be the ultimate goal of war. The human person naturally wishes for peace; even those who wage war seek to create peace in the end (Augustine of Hippo 1967:866–70). And peace within the Roman Empire required the use of force at times, just as political order within a society requires punishment. In a letter to one commander in the field, Augustine reminds him that while the goods of this world are ephemeral, they do at least create a state of peace that is necessary for human existence (Letter 189, to Boniface, reprinted in Augustine of Hippo 2001:214–18). Both punishment and war are understood to be tools for keeping order but tools that should be used with great discretion and even sorrow.

Augustine’s views on war need to be understood in his particular political context. As a bishop of a new faith that was being blamed for the collapse of the Roman Empire, Augustine felt the need to demonstrate that Christians could engage in combat as much as the Romans could. In light of his physical location on the outskirts of the Empire, where various groups were engaged in attempts to topple the authority of Rome, Augustine saw the need for the judicious use of force.

After Augustine, reflection on war and peace in the Christian tradition evolved in different ways. One, the just war tradition, will be explored in more depth below. Another, the holy war or crusading tradition, flourished as the Christian community undertook large-scale military actions to recapture the Holy Land, primarily Jerusalem, for Christianity (Riley-Smith 1987; Reichberg et al. 2006:98–103). This tradition of thought was promulgated by popes who gave sanction to the use of military force against Muslims, Jews, and even Eastern Orthodox Christians. Outside of the just war and crusading traditions, pacifism was another route the Christian tradition took concerning matters of war and peace. As noted above, the early Christian Church was largely pacifist, although there continues to be debate about this. A key figure in the Renaissance tradition, Erasmus (1466–1536) argued against the just war tradition and sought to emphasize both the classical and Christian sources of pacifism (Dallmayr 2004; Reichberg et al. 2006:233–9). The “peace churches” such as the Quakers and Mennonites have continued this tradition.

The Classical Traditions

The Ancient Greek Tradition

Perhaps the most important text for the classical traditions is Homer’s Iliad. The Iliad, the story of the war between the Greek city-states and the Asian power Troy, became the touchstone for understanding war and peace throughout the Greek and Roman eras. Drawing norms from this largely oral epic is difficult, not least because translations of the Ancient Greek text do not always capture the complexity of the normative assumptions that structured military life at the time (Adkins 1972). Moreover, most scholars assume the war described took place around 1200 bce while the final written form of the Iliad probably appeared around 800 bce. As a result, there is a mix of normative assumptions throughout the text, ones combining different social and political structures over a 400-year period.

Despite these difficulties in history and translation, one can identify key norms within the Iliad. The first and most important is honor. This is best seen in the fact that rather than large unnamed enemies fighting each other, the Iliad names each and every warrior as he engages in battle. Nor is the naming limited to one side; Greeks and Trojans are remembered through their unique histories as they fight and die. Another key norm to be found in the Iliad is the importance of respecting the bodies of the dead. Ironically, this norm is emphasized in its breach, most famously in the scene of Achilles desecrating the body of Hector after their hand-to-hand combat.

But the Iliad does not simply celebrate war, as some modern commentators believe (Kaplan 2002). The opening lines of the text emphasize that war emerges from rage, an uncontrolled emotion that does not deserve to be celebrated; indeed, the god of war, Ares, is often characterized as being unable to control his emotions. At the end of Book 5, Zeus, the king of gods, describes how much he hates Ares because he cannot be controlled and because he wreaks so much havoc on humanity. One author argues that Ares is really the god of violence, while Athena, the goddess of wisdom (who is traditionally pictured in a war helmet) is actually the goddess of “organised, disciplined, rationally conducted collective activity,” i.e., war by a city-state (Neff 2005:16).

The Greek tradition evolves, of course, and it is with what is sometimes called the Classical period that new norms emerge. Captured in the historian Thucydides’ account of the Peloponnesian War, these norms continue to emphasize the Homeric norms of honor, but the individual becomes less important as the city-state emerges as the central agent of war (Garst 1989; Johnson 1993; Crane 1998; Lebow 2003:65–167). For Thucydides, three norms motivate the warrior: honor, fear, and profit (Lebow 2003). One of the most interesting shifts is the importance of ad bellum justifications for war. The Iliad famously starts in the middle of the war; we know the reasons for the war only because we know the myths of Greece and Troy. The Iliad was not concerned with justifying why war broke out, because war had simply been something that had long been in existence. In Thucydides’ account, on the other hand, there is an extended discussion of what justifies the Athenians waging war against the Spartans (Thucydides 1972: Book 1).

The Roman Tradition

The Greek tradition informs the Roman tradition. Rome rises to power in the second century bce, dominating the region for the next 600 years. Its dominance was embodied in warfare, particularly its ability to extend its empire through military means. Unlike the Greek tradition, where norms and rules can be found in a few specific texts, the norms and rules – and eventually laws – that governed the Roman approach to war are not so easily located. This may be because Rome, as an ever-expanding empire, slowly constructed a set of rules that evolved into an international legal structure concerning the use of force.

Roman international law as it relates to warfare begins with a largely religious process, the ius fetiale. This originated in the role of the College of Fetials, essentially a body of priests who were also vital in diplomacy. As described by the Roman historian Livy, the rules included a formal demand for redress by the Romans against their enemies, who were allowed 33 days to respond. If they did not offer anything for their affront to the Roman state, one of the priests would throw a spear across the border, which had to be undertaken in the presence of at least three enemy soldiers (Livy, History of Rome, I.32, reprinted in Livy 1960:69–70). These procedures evolved as Rome began to wage war outside of its immediate borders, including consecrating a part of the Roman Forum as “enemy territory” into which the spear was thrown (Neff 2005:28).

This largely symbolic procedure seems more about actually declaring war than imposing any norms, rules or laws upon it, about which there is some debate among classicists (see Harris 1979:166–74 for an overview). Some argue that the procedure moderated aggressive war by forcing the Romans to demand redress for some affront; while it could certainly be a false justification, the need to justify the war to both the Roman community and the enemy at least disciplined the urge to war and expansion (Wiedemann 1986). Cicero, the Roman philosopher whom some see as central to the early just war tradition (Bellamy 2006:19–20) saw the ius fetiale as important for disciplining warfare, which he believed provided a set of clear rules that should guide war (Cicero, On Duties I:36, reprinted in Cicero 1991:15–16).

Rome and Greece, in other words, while not necessarily “living traditions,” have most certainly impacted the development of modern norms, rules, and laws concerning international security in the current international order (Kaplan 2002; Coker 2008). In some ways, such as the creation of natural law, these influences are perhaps more important than the Judeo-Christian tradition. Yet, they all shape and inform the way in which we evaluate international security.

Islam and War

Islamic conceptions of war and peace have appeared in the public eye recently as a result of various political and military interactions between the USA, Europe, and parts of the Islamic world. From the Iranian revolution of 1979 to the current “war on terror,” debates about what role Islam does and should play in the international normative order have created a cottage industry of books and articles. Surprisingly, not much of this literature has directly addressed the issues of this chapter: namely, an ethic of war, violence, and security.

To understand the Islamic approach to war and peace, certain features of the tradition are important to keep in mind. First, unlike in Christianity, the founder of Islam was the leader of a political community. When Mohammed immigrated to Medina at the invitation of the elites of that city in ad 622, the beginnings of a formal political community were inaugurated (Watt 1961:82–101). This community soon engaged in a systematic expansion, pushing forward the new religion of Islam into communities that were most often receptive to it. As a result, while fighting did take place, a number of communities embraced the new faith, giving Mohammed and those who followed him experience in both war and diplomacy.

The second important feature of Islam is the centrality of law. Islam, like Judaism but less so Christianity, is a highly law-governed tradition. Most debates about specific norms, rules, and laws in Islam are based upon the interpretation of legal texts (see Schact 1979; al-Azami 1996). While the Quran is the primary text, it does not yield as easily to interpretation. Unlike the Judeo-Christian scriptures, the Quran does not follow a chronology nor does it have a specific set of norms spelled out concerning war and violence. The second important text, and sometimes more important, is the sunna (sometimes as hadith), or body of writings on the activities of the Prophet Mohammed as they relate to both the daily life of the individual Muslim and the political structures and policies of the rapidly growing community. These texts have led to the creation of sharia, the body of Islamic law that governs the life of the individual Muslim and the Islamic ummah, or community as a whole. The interpretation of these texts as they relate to dilemmas of daily life is thus the central issue for finding the norms, rules, and laws that relate to international security from an Islamic perspective.

For obvious reasons, much of the debate about how to interpret these texts takes place in Arabic. At the same time, Muslims are not solely in the Arab-speaking world; the largest number of Muslims in any one state is in Indonesia, and a growing population exists in Europe (Ramadan 2004). Even more relevant for the purposes of this essay, when individuals such as Osama bin Laden produce interpretations of these texts, sometimes referred to as fatwas, that justify violent actions in relation to North American and European populations, these interpretations become part of a larger discursive community. The debate over who should be allowed to interpret these texts has been subject to a great deal of debate in the Islamic world. Traditionally, only the ulema, or scholars of the law, could undertake such authoritative interpretations, ones that took place within the confines of the four traditional schools of Islamic law. While interpretations by individuals such as bin Laden have received the most interest, the power to interpret these sacred texts has been altered in recent years by the emergence of new communities of young Muslims (Mandaville 2007).

As a result of the wide range of interpretations and texts, it is difficult to identify a single Islamic view on the ethics of international security. A few scholars in the field of international law and ethics have sought to make sense of this wide range of texts. One of the most important works in English is Majid Khadduri’s translation of Mohammed Shaybani’s Sharia Kitab As-Siyar, one of the first texts on international law in the Islamic tradition (Khadduri 1966; see also Khadduri 1955). Shaybani was an eighth century Islamic philosopher, a leading figure in one of the Islamic schools of law. The text explores not only questions of war and peace but how the Islamic empire should relate to other communities through diplomacy. For Shaybani, the use of military force was most certainly allowed, but it was to be moderated by concerns about innocents and injunctions not to force conversions of individuals to Islam. At the same time, within the realm of the Islamic empire it did emphasize the authority of the caliph in establishing order, through force if necessary.

A concept developed at the time of Shaybani’s text was the distinction between the dar al Islam and the dar al harb, or the abode of Islam and the abode of war. This geographical distinction was intended to differentiate the ethics of war allowed within the Islamic community and those outside of it, as described in Shaybani’s work. Today, this distinction is evoked in some interpretations of Islamic ethics, although others have questioned its applicability in a world in which Islamic governments are rare and Muslims are widely dispersed (Ramadan 2004:62–101).

Some have argued that there is a strong parallel between Islamic teachings on war and peace and the just war tradition. John Kelsay has made this case most clearly, arguing that there exist ad bellum norms and in bello norms that map quite closely onto the Christian-inspired tradition (Kelsay 1993). Recent work by Sohail Hashmi has connected Islamic political ethics most directly to issues of war and peace (Hashmi 1996; Hashmi 2002).

The Just War Tradition

Post-Augustinian Evolution

As noted above, the Christian tradition after Augustine evolved along a number of different tracks, including pacifism, holy war, and just war. The last of these has perhaps been the most influential, primarily for the role it has played in constructing the international legal tradition (Best 1994:14–66). The tradition as an explicit moral one was subsumed into international law during the nineteenth century, but re-emerged in the mid-twentieth century. Today it has become an influential source of critical reflection upon both legal and practical dilemmas in international security, informing a wide range of debates around the world. It is no longer a purely Christian tradition, although Christian churches continue to draw upon it in formulating their statements about war and peace (Johnson 2007; Biggar 2007).

The core of the just war tradition rests on the idea that not all ends justify the use of force and that even when ends are accepted as just, not all means are justified to achieve these ends. The just war tradition, therefore, proposes certain legitimate reasons to go to war ( jus ad bellum) and criteria of acceptable behavior during war ( jus in bello). In recent years, a third category of ethical reflection has been added, jus post bellum, or the norms, rules, and laws that should guide the way a post-conflict situation is handled. It is important to keep in mind that the just war tradition is a framework for evaluating the use of force and “not a weapon to be used to justify a political conclusion or a set of mechanical criteria that automatically yields a simple answer, but a way of moral reasoning to discern the ethical limits of action” (United States Council of Catholic Bishops 1993:6).

Following Augustine, Christian reflections on war and peace moved to the canon lawyers who helped turn Christian theology into practical rules of statecraft. Much of this work focused on commentaries on respected authorities, such as Gratian’s Decretum. Gratian, a twelfth century monk, sought to harmonize a large body of legal rules, papal decrees, and real-life political and religious dilemmas. These canons became central to the development of the just war tradition (Johnson 1981:122–71).

As with almost every element of Christian thought, Thomas Aquinas, the thirteenth century Dominican theologian/philosopher (1225–1274), played a key role in pushing the tradition forward. Aquinas wrote very little directly on war, but his use of Augustine and the canon lawyers elevated the issue of just intention and authority in the tradition. While these were key parts of Augustine’s thinking, the focus of the tradition had for some time been on the issue of just cause, or what issues justify the use of force at all (Reichberg et al. 2006:169–98). A key figure who drew upon Aquinas was the fifteenth century theologian Francisco de Vitoria (1492–1546). Writing from within the “School of Salamanca,” Vitoria examined justifications for war in relation to the discoveries of the new world (Vitoria 1991). He emphasized that because we cannot be sure of which side is just or not, it is central that those engaged in warfare conduct their operations in accordance with shared standards, thus helping to legitimize the jus in bello rules. This was not a claim of relativism, for Vitoria believed that there existed a just and unjust side in war; rather, his argument was that because only God knows the true just side, all sides must act with special care when waging war.

The next key figure in the tradition is Hugo Grotius (1583–1645). Grotius, often considered the “father of international law,” published The Rights of War and Peace in 1625 (Grotius 2005). He argued that justifications for using military force could be based on natural law, or the laws that arise from understanding of the human person and the world. Grotius was part of a larger intellectual movement of the time in developing natural law as a counter to the purely Bible-based accounts of war and peace that had dominated the medieval period. For the purposes of the tradition, he carefully explained the three classic just causes: self-defense, punishment, and retaking what had been taken. Although he placed more emphasis on punishment than the modern tradition does, he laid down with great clarity the structures of how the tradition should view just war (see Tuck 1999).

Following Grotius, other figures helped to turn the largely Christian just war tradition into a more generally secular tradition of international law; key figures here include Samuel Pufendorf (1632–1694), Christian von Wolff (1679–1754), and Emmerich Vattel (1714–1767) (for texts, see Brown et al. 2002:311–77). A separate essay deals with the international legal tradition, so these developments will not be addressed in much detail here. During the nineteenth century, however, the emergence of positivism as a foundation for international law meant that the just war tradition, with its explicit combination of law and ethics, faded into some irrelevance (other than in Catholic social and political thinking, where it continued to play a prominent role). In the mid-twentieth century, however, just war returned to some prominence. The failure of international law to regulate the outbreak and conduct of both world wars led some to recognize the need for a return to alternative sources for the norms and rules that could moderate war. Two further developments generated renewed interest in the just war tradition. First, the rise of nuclear war as a potential reality and the creation of a Cold War climate led a number of thinkers to return to the tradition (Ramsey 1961; 1968; Tucker 1978). When the US Conference of Catholic Bishops addressed this issue with a pastoral letter in 1983, it raised the prominence of the tradition in public discourse (United States Conference of Catholic Bishops 1983).

A second development was the decolonization movement and military conflicts that resulted from revolutionary movements. These movements were a challenge to jus ad bellum, as they fought for the norm of self-determination, and to jus in bello, as they used strategies and tactics that did not conform to the ways in which international law structured combat. Partly in response to these developments, Michael Walzer published Just and Unjust Wars, which became a modern-day classic in the field (Walzer 1977). Walzer’s account of the tradition did not draw on the Christian tradition in any depth, but based its analysis on what he called the “statist paradigm.” This approach found the primary justification for the use of force in the protection of the political community (see also Orend 2000; Walzer 2004).

Especially since the end of the Cold War, thinking within the just war tradition has flourished. A few academic journals played a key role in keeping the tradition vibrant during the Cold War and continued to publish important works on it afterwards; perhaps the most important here is the New York based Carnegie Council on Ethics and International Affairs journal, Ethics & International Affairs. Some works built upon the tradition, both its Christian and natural law dimensions (Elshtain 1992; O’Donovan 2003; Elshtain 2003; Reed and Ryall 2007). Some have sought to move the tradition to more of a theory, a move that reflects an important shift in thinking about just war. These works have sought to bring the formal study of normative ethics to bear upon just war, sometimes ignoring the history of the tradition. While some important and innovative works have arisen from this approach, its neglect of the history of the tradition raises some important questions about how to deal with normative evolution (McMahan 2002; Evans 2005; McMahan 2009). Certain philosophy journals have developed this side of the tradition, particularly the Journal of Political Philosophy and Philosophy and Public Affairs. Some works have tried to combine a more analytical and traditional approach to just war (Norman 1995; Coppieters and Fotion 2002; May 2005; 2007; 2008; Bellamy 2006; Steinhoff 2007).

This proliferation of works on just war has reinforced its importance for understanding the role of norms, rules, and laws as they relate to war. The just war tradition is certainly not the only way to address these issues; a body of literature on pacifism has also become central to understanding war and peace, some of which is explicitly critical of the just war tradition (Teichman 1986; Miller 1991; Yoder 1996; Allan and Keller 2006). A number of works have sought to bring together various traditions, including just war and pacifism (Atack 2005; Sorabji and Rodin 2007). The fact that the just war tradition became the analytical mode through which the new “Responsibility to Protect” doctrine was developed demonstrates its continued importance (International Commission on Sovereignty and Intervention 2001).

Key Components of the Tradition

Just Cause

This essay, because of space, does not include all elements of the tradition. Those omitted include last resort, probability of success, and comparative justice. The ones listed here – just cause, right authority, right intention, proportionality, and discrimination – capture the most important dimensions of the tradition.

Just cause is the idea that force is used for a justifiable reason. Traditionally, there were three just causes: self-defense, punishment, and retaking what had been taken. As international legal norms and rules came to dominate the international order, the primary just cause came to be self-defense against aggression. Some have explored the return of other just causes, such as punishment (Lang 2008; O’Driscoll 2008). Others have begun to call into question the centrality of self-defense as the primary just cause (Rodin 2003; Rodin et al. 2004).

Another development in the just cause category, one related to the question of self-defense, concerns preemptive and preventive military actions. Prompted by the attacks of 9/11 and the Bush administration’s decision to attack Iraq on the basis of a possible future threat, a debate has arisen about the justification for preventive war (Lang et al. 2003). The administration developed its argument for this new approach to self-defense in its 2002 National Security Strategy document, one that fundamentally redefined the notion of preemption (Bush 2002). Some traditionally liberal IR theorists have proposed normative reasons for creating an institutional structure for waging preventive war (Buchanan and Keohane 2004; Doyle et al. 2008). Legal theorists have struggled with appropriate rule-governed responses to preventive military action (Franck 2002; Dershowitz 2006). A number of philosophers have also addressed this issue at some length (Shue and Rodin 2007). A few ethical arguments have been made to support preventive war (Kaufman 2005). Richard Miller has used the concept of just cause to assess critically the 2003 war against Iraq, determining that a rigorous use of the category undermines the justice of the war (Miller 2008). Jeff McMahan has generated debate about the principle of just cause by linking it to the issue of individual liability in warfare (McMahan 2005; Hurka 2007).

Right Authority

Right authority is the second criterion of jus ad bellum. It suggests that war must be declared by those who are responsible for public order, not private groups or individuals. The intent of this condition is to narrow the spectrum of entities able to wage war, and to ensure that the decision to wage war is made by a legitimate authority. Who is considered the legitimate authority, however, is an issue of contention. Over the course of history, shifts in just authority have occurred, the largest one marked by the creation of the Westphalian system (named after the Treaty of Westphalia in 1648). Considered a pivotal stage of power transition, the Westphalian system was the first step in the shift of legitimate authority from religious institutions to sovereign states. With the advent of democracy in the nineteenth and twentieth centuries, state leaders became accountable to their citizens, who demanded to know why they were being forced to take up arms for the national interest.

The central dilemma of authority is what role should be played by the United Nations and other international structures in authorizing the use of force. As the concept of peacekeeping has developed in recent years, the authority of the United Nations has become a more contentious issue. When the UN Security Council was avoided by the great powers in the Kosovo (1999) and Iraq (2003) conflicts, important questions were raised about its legitimacy when it comes to the use of military force (Cronin and Hurd 2008). Others have suggested normative justifications for how international organizations can be more formally structured to respond to a broad range of threats (Keohane et al. 2006).

Right Intention

Like other moral theories, the just war tradition suggests that the intentions of the agents are important to consider in evaluating actions. This is related to the just cause criteria, but different in an important way. For example, one might argue that, objectively, a war can be labeled just because it leads to the destruction of an evil regime. But, if those undertaking the war intend simply to increase their nation’s power, advance their personal financial or political interests, or achieve fame and fortune, then the validity of the war may be called into question. In point of fact, it is more accurate to call this category “right motive,” as Terry Nardin has suggested. In philosophy, an intention is the declared reason for action, while a motive is the issue or concern that motivates an individual to undertake an action. In other words, the category of right intention should probably be known as right motive (Nardin and Williams 2006:10).

Michael Walzer has pointed out that no individual or government really ever has truly pure motives (Walzer 1977:26). But, at the same time, the question of hypocrisy is one that bedevils anyone interested in ethics and international affairs. That is, if individuals profess to be acting for morally good reasons but are discovered to be acting for morally suspect ones, then their future actions will constantly be called into account. Those who have criticized the recent surge in moralism in humanitarian intervention and other uses of military force rely heavily on this kind of critique (Chomsky 1999; Chandler 2002). As a result, the tradition’s emphasis on the centrality of right motives is an important discipline upon excessive moralism.


Proportionality is a criterion of both jus ad bellum and jus in bello. In terms of jus ad bellum, it attempts to ensure that the damage and costs of war, in both human and physical terms, are proportionate to the benefits expected as an outcome of war: that is, it seeks to take into account the grand strategy of pursuing a war rather than specific strategies and tactics of war.

In light of the overwhelming superiority of the US military, some believe any use of force by the USA will violate the proportionality criterion. Neta Crawford’s recent work on the just war tradition and the US response to 9/11 raises precisely this issue (Crawford 2003). The growth of US power in the international system has created what many argue is a situation of asymmetry, which may increase the chances that opposing states and non-state actors will utilize terrorist and irregular warfare, further complicating the ability of the USA to respond proportionately to attacks.

In jus in bello, the proportionality criterion reflects the commonsense assumption that warring communities should not reply in excess to attacks on them. There exists no mathematical formula to determine what is proportional, however, so evaluating proportionality remains a matter of prudential judgment (Franck 2008). One could argue that attempts to place limits on the collateral damage that non-combatant entities may sustain during a war, in the hopes that the good outweighs the costs of a war, represent a form of proportionality. While it is acceptable to have a certain ratio of non-combatant/to combatant casualties, it is imperative that the intent of the attacks is to produce more good than bad. In other words, means must justify the ends and those means utilized to pursue just ends must be set in a morally restrictive framework.

One version of the proportionality criterion is the idea of double effect. This concept, examined by Aquinas among others, stipulates that if a military action is not intended to kill civilians but does so in the course of accomplishing a military objective, then it can be considered morally licit. This is a contested concept, however, for it allows individuals to explain away violations of the proportionality criterion without having to consider the seriousness of their violation.

One area where the question of proportionality has become prominent is in aerial warfare. The Hague Conventions do not include any laws concerning aerial warfare, although there is an important document called The Rules of Aerial Warfare (1923, reprinted in Roberts and Guelff 2003:139–53). Ward Thomas has explored how a set of norms evolved concerning aerial warfare (Thomas 2001:87–180).


The last principle is discrimination. It states that just authorities engaged in combat must only fight persons also engaged in combat. Bystanders must not be targeted, and cannot play a role in combat unless participating in either a formal military service or a uniformed militia. Furthermore, prisoners of war are entitled to specific rights and treatment. These elements of the tradition have been most clearly translated into laws rather than simply rules or norms. These laws have been codified in the Geneva Conventions of 1949 and the additional protocols of 1977 (reprinted in Roberts and Guelff 2003). The specifics of the conventions will not be addressed in any detail in this essay, since they are dealt with elsewhere in this Compendium.

Distinguishing soldiers and civilians may seem to be an easy task, but modern warfare has made this much more complicated. As some theorists have noted, new forms of “humane warfare” have challenged our understanding of what constitutes a soldier (Ignatieff 2000; Coker 2001). The increased role of civilians in the technology of warfare has also raised important questions about how they should be considered: for instance, what is an individual sitting at a computer terminal who does not necessarily wear a uniform but who may control battlefield operations (Dunlap 2004)?

While the distinctions have become more complicated, violations of the rules and laws governing this area of conflict have created a large-scale international judicial structure. War crimes tribunals and international criminal courts have flourished since the end of the Cold War. Some theorists have linked the courts back to the just war tradition (Johnson 2004; May 2007), although others have raised important normative questions about what these courts can and cannot do (Branch 2007; Simpson 2007).

Emerging Challenges in the Ethics of Security

A wide range of issues could be considered as challenges to the broader theoretical ethics described above. Nuclear deterrence, humanitarian intervention, global health, and the environment all deserve more treatment as posing challenges to our understanding of ethics at the global level. For purposes of space, this essay will touch on two recent developments that raise a wide range of issues within the ethics of security – post-conflict justice and counterterrorism policy.

Ethics of Post-Conflict

As the international community has progressively become engaged in the reconstruction of post-conflict societies, analysts of international affairs have focused their attention on these dynamics. In point of fact, “reconstruction” is not a new endeavor for the international community (Williams 2006). Much of the literature on post-conflict reconstruction, however, has focused primarily on the more recent past. Some of the literature has focused on creating a peaceful order, while others have addressed the difficulties of creating a just political order (Teitel 2000; Mani 2002; Richmond 2002; Zaum 2007; Kerr and Mobekk 2007).

Whether to focus on peace or justice is an ethical dilemma. The distinction between the two is, of course, not very clear, but attempts to create peace sometimes focus on short-term imposition of policies rather than long-term attempts to reconstruct political institutions. At the same time, in situations where violence is just below the surface, the need to impose a peaceful order may take precedence. In light of the importance of authority that this essay has highlighted, efforts to construct political institutions, particularly those labeled as “rule of law” initiatives, are becoming more important. This rule of law approach has become a central part of many UN-led post-conflict interventions. For instance, in East Timor and Kosovo, the UN had full judicial authority for short periods – a much more extensive form of control than in other post-conflict situations, where the role of the UN was mainly to facilitate the creation of new judicial institutions (Chesterman 2004:154–82).

To understand the issue, consider humanitarian intervention. When international forces undertake a humanitarian intervention, usually involving a strong military presence at first that only eventually transitions into more civil society programs, attention is paid to the creation of a secure environment through force of arms. When it comes to ensuring public order and obedience to the law, too often military/police forces, which are not backed up by a functioning prosecutorial, judicial, and penal structure, will end up detaining and even informally punishing those who serve as “spoilers” or even common criminals. These punitive measures undertaken by those whose primary goal should be the investigation of crimes and arrest of suspected criminals distort the just application of sentencing procedures. Rather than engage in just punishment, these military/police forces, often internationally trained and even including international police forces, distort the rule of law and justice. Such issues raise ethical and political complexities that are being addressed through both legal and ethical literature, such as in the jus post bellum approach that has developed in recent years (Orend 2002).

Ethics of Counterterrorism

Terrorism as a subject is sometimes seen in simplistic terms; all terrorism is evil, which makes any policy in response justified. Yet, as the events of 9/11 and the American response have demonstrated, such simplistic notions do not lend themselves well to ethical reflection. The ethical dilemmas in responding to terrorism have been front and center in recent international affairs (Bellamy 2008).

The first dilemma that one can identify is whether or not terrorism should be treated as a criminal justice or a military problem. If it is a matter of criminal justice, then the standards of domestic police investigation, detention, and trial should be the proper response. If it is a matter of war, then military means of search and destroy are the proper responses. This question did not appear anew after 9/11, but has been part of the debate about how liberal states should respond to terrorism; Paul Wilkinson was writing on this subject back in 1977 (Wilkinson 1977; see also Wilkinson 2000). Debates about which approach are morally justified have characterized a great deal of the debate since then (Booth and Dunne 2002; Evangelista 2007). International legal scholars have also struggled with the proper response, usually trying to balance state sovereignty with stopping an international crime (Murphy 1986; Erikson 2002). As one forum put the question, after 9/11 do we need new rules governing the international system and the use of force as a whole (Falk et al. 2002)?

Specific policy responses that make up counterterrorism policy have generated their own debates. One response that has been taken up by the Israeli military structure is targeted killing, which some claim the USA has also undertaken in its attacks in Yemen in 2002 (David and Stein 2003; Schmidt 2008; Plaw 2008). Some have called this assassination by another name, but others have argued that to target terrorists directly avoids harming civilians. Another issue that has raised debate is the detention and interrogation of terrorists. Much of this debate has centered on US domestic law: that is, whether or not the Bush administration’s policies conform to American understandings of the law governing combatants.

A further issue has been the rendition and detention of suspected terrorists and use of coercive interrogation tactics against such individuals. These tactics, which most everyone calls torture, have been justified by the US administration of George W. Bush. While very few have tried to defend these tactics as torture, the debate concerns what rules should apply to individuals who do not declare themselves to be combatants yet use military force against civilian and military targets. The detention of individuals at Guantanamo Bay, Cuba and the scandal of abusing individuals in the Abu Ghraib detention facility in Iraq have made these issues of public debate in the USA and around the world, with much of that debate centering on questions of norms, rules, and laws. The literature on this issue has burgeoned in the last few years (Dershowitz 2002; Levinson 2004; Greenberg and Dratel 2005; Brecher 2007).

Some have argued that to justify any form of violence with formal ethical analysis makes it more acceptable and is thus, in itself, wrong. This essay has hopefully dispelled this false notion. If ethics is simply about developing rules that outlaw various kinds of things, then it may be that ethical reflection on war should go back to the sixth Commandment – Do not kill. But, if ethical reflection is more than simply finding laws but also includes investigating the norms, rules, and laws that regulate war, violence, and security, then it must do more than simply condemn.

The introduction to this essay also noted that ethics cannot be abstracted from the political context within which norms, rules, and laws develop. It is for this reason that justice is so important for understanding the normative dimensions of war and peace. A just political order is one in which certain kinds of norms make sense, for they are connected to the legitimate structures of authority. The challenge for scholars of ethics and international affairs is to consider whether or not there can be such a conception of justice at the international level. If so, does this imply that all norms and ideas must at some level be the product of a single community? In that this does not seem possible anytime soon, the international system will continue to struggle with the tensions between conflicting normative structures and political systems. At certain points, these norms generate conflict themselves, but they need not necessarily do so. The hope is that through understanding the sources and contexts of norms, rules, and laws, a more secure international order will emerge.


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This essay has been greatly improved as a result of critical readings by Cian O’Driscoll, Will Bain, Jeremy Gabrielson, John Williams, Theo Farrell, and the reviewers. All errors are, of course, my own.