Why Stoics Would Embrace Just War Theory — by William C. Spears

Editor’s Note: The following is an excerpt from Stoicism as a Warrior Philosophy: Insights on the Morality of Military Service, by Commander William C. Spears, USN, adapted for publication in Stoicism Today.

Had the ancient Stoics endured as a discrete philosophical school, it is reasonable to believe they would assent to the core principles of just-war thinking that enjoy consensus today. Like modern moral theorists, they would likely disagree and debate at the margins, challenging one another with urgency. On some specific points, they would veer sharply from conventional just-war thinking, with reasons and caveats I address in my book, Stoicism as a Warrior Philosophy. But it is not as simple as saying they would subscribe to just-war theory, as if that were some monolithic and self-evident truth. We should be able to say something about why they would believe what they believe and where disagreements might arise. First, though, we should acknowledge a rather obvious question: why would Stoics even bother moralizing about war?

If death and misery are actually indifferents, we might wonder why Stoics would perceive any obligation to offer protection to noncombatants or to exercise any degree of restraint toward enemy combatants. A Stoic warrior might ask, “If I am to regard my own life as indifferent, then why should I hold any regard whatsoever for the lives of noncombatants or of my enemy? Why must I subject myself to a different standard?” It is a fair question. The restrictions we, as a society, impose upon our warriors come at real costs both to their safety and their immediate combat effectiveness.

The question touches upon what I call the problem of other peoples’ indifferents, which I address in detail in my book’s fifth chapter. In this instance, the question fallaciously compares the way I should feel about one thing with what I should do about another. Even if I am to regard my own life as a moral indifferent, it does not follow that I should forgo all effort to preserve or improve it, as would be expressed through the appropriate selection of preferred indifferents. Likewise, even if I am to regard the welfare of my neighbor as a moral indifferent, it again does not follow that I can deny any moral responsibility concerning it. The specific balance to be struck between my neighbors’ interests and my own is a different moral calculation and, by all available evidence, Stoics expect both can be served in harmony when interests are identified correctly. Problems arise when someone misidentifies what is actually good.

Even when I interpret my impressions with sagacious precision, I might have cause to war on account of my neighbor’s foolish actions. A common view of such circumstances is that war becomes a “necessary evil” or a “lesser of two evils.” Stoics would plainly reject this; specifically, they would deny the possibility an appropriate action can be considered evil. For an action to be appropriate, it must have both consequentiality and reasonableness, which means it is defensible according to the standard of a sage (Brian E. Johnson explains this well in The Role Ethics of Epictetus). If a given action is justified in light of all available information, then it is simply the right thing to do, regardless of any apparent wrongs “conditioned by” the circumstances.

Instead of viewing war as a necessary evil, Stoics would regard it as the potential winner among competing moral duties. As we know, certain indifferents such as poverty or sickness are typically dispreferred unless their preference is “conditioned by” exceptional circumstances (see DL 7.104; 7.109). Likewise, certain behaviors, such as telling the truth, are also normally appropriate in that they are consequent—meaning they follow from nature—when considered in isolation from important contextual factors. Such behaviors might lack reasonableness in light of exceptional circumstances, such as villainous secret police at the door. In such cases, consequentiality can be overridden by the prevailing circumstances.

As well-articulated within William David Ross’s theory of prima facie duty, all humans are bound by a duty of non-maleficence—an obligation to avoid causing harm—against which all war decisions must be evaluated. This duty is inherently binding and carries significant moral weight, typically outweighing other ethical obligations, such as the duty to provide aid. However, non-maleficence is not absolute; it can be overridden by sufficiently compelling circumstances. For instance, a justified belief that refraining from the use of force would lead to even greater harm or loss of life might warrant an exception. Alternately, non-maleficence might be overridden by the belief capable nations should respond with force when malevolent actors disrupt the international system. One might justifiably desire such action as a universal law if they truly believed a better and more-stable world would result. Notably, none of this would apply in a world of sages.

On these bases, pacifism and absolute commitments to nonviolence create perverse moral outcomes upon contact with the real world. It is not just that humans can’t be pacifists because they are imperfect, it’s that even perfect humans could not be pacifists while other humans are imperfect. This would be as true in a Stoic moral system as it is in any other and, accordingly, war and military service are no less morally compatible with Stoicism than they are with any other peace-promoting philosophy. It is why virtually every country possesses some capabilities of self-defense, while exceptions to this rule subsist under the aegis of powerful security guarantors. Notably, this says nothing about the appropriate level of investment in such capabilities or how they should be employed, which are questions of policy that merit individual evaluation, and about which reasonable people can disagree.

Because it follows from nature for all reasoning humans, the fundamental duty of non-maleficence is self-evident and role independent. Within the Epictetan framework, this means it cannot be overridden by the obligations of specific roles. As a warrior, then, my duty to pull the trigger, to service the target, or to order the launch of a missile—my duty to kill—cannot follow from my role as a warrior. Instead, my duty to kill must originate from within my identity as a virtuous and rational human being. Where specific roles might come into play is in tipping the balance between conflicting human duties, such as the duty of non-maleficence as weighed against a duty to defend an ally from invasion—both of which follow directly from reason. If killing is what I must do, it must not be because I am a good warrior, but because I am a good human. The fact I am a good warrior helps define what kind of good human I am.

Any claim that non-maleficence has been overridden must overcome a high burden of proof. Reasoning through this justification naturally leads to a set of necessary and sufficient conditions for such an override. At the scale of collective action, these conditions inevitably resemble what are traditionally recognized as just-war criteria.

Consider, for example, the decision to wage war, which requires the subordination of individual preferences to the judgment of a collective. Suppose it is clear to me that waging war is the appropriate action for my country, a larger Hieroclean circle of which I am but one member. I cannot independently act on this belief. Instead, such decisions must be made by a legitimate authority vested with the power to act on behalf of the collective within the established system of governance. Modern theorists argue legitimate authority is a prerequisite for satisfying any other jus ad bellum criterion because it is specifically this authority that must evaluate and apply those criteria. If the deciding authority is not legitimate, then it is impossible to say that other jus ad bellum criteria have been correctly evaluated.

When committing a country to war, the legitimate authority must do so for a just cause. This means the duty or obligation said to override non-maleficence must be a serious one. Frivolous glory projects and opportunistic acts of aggression hardly meet this standard. Likewise, actions driven by pride or desires for vengeance fall short of just cause, as there is no corresponding duty strong enough to outweigh the fundamental obligation to avoid harm. Moreover, non-maleficence cannot be overridden without a reasonable chance of success; indeed, it would be imprudent to undertake even a morally neutral endeavor without a realistic prospect of achieving the desired end. When the endeavor involves overriding a fundamental moral duty, the burden of justification becomes that much higher.

Tightly linked to just cause is the requirement its pursuit genuinely motivates the deciding authority, a principle embodied in the criterion of right intention. This demands freedom from ulterior motives or passions such as fear, pride, greed, or hatred, which undermine integrity—the alignment of virtues, values, and actions—at both the societal and individual levels. Such contaminants poison the decision-making process, distorting judgment and obstructing paths to peaceful resolution of conflict.

If there is a realistic way to address the overriding duty without compromising the duty of non-maleficence, that path should be chosen. As Cicero says, “There are two types of military dispute, the one settled by negotiation and the other by force. Since the first is characteristic of human beings and the second of beasts, we must have recourse to the second only if we cannot exploit the first” (On Duties 1.34). Therefore, the decision to wage war must be reserved as a last resort. Discussions of last resort often intersect with the concept of a formal declaration of war, which some view as a final measure of persuasion. Cicero preempted later theorists on this point as well, arguing “no war is just unless it is preceded by a demand for satisfaction, or unless due warning is given first, and war is formally declared” (On Duties 1.36).

While few serious theorists defend this view, an intuitive argument suggests that once war is underway, all methods are justified to bring it to an end. This perspective has been echoed by various figures throughout history and is perhaps best captured in the expression of General William T. Sherman before destroying the city of Atlanta: “War is cruelty, and you cannot refine it.” This view is often paraphrased “War is hell.” Such reasoning flows naturally from the belief war is a necessary evil. If war is inherently evil, it disconnects entirely from moral reasoning, such that all actions are equally impermissible and therefore none are worse than others.

This view, however, is deeply deficient. For one, peace, when treated as an end in itself, is a bad priority. The shortest path to peace is surrender, and the second shortest is to “create a desert and call it peace.” Both options are readily available, especially in modern times, and they grow more tempting with every setback or frustration. Yet, as has been observed since at least the time of Cicero, only a just peace is lasting and all war decisions should support its achievement. Even from a purely pragmatic standpoint, then, violence that is unnecessary, indiscriminate, or disproportionate should be eliminated.

Practical observations aside, the view that war is always unmitigated cruelty is simply lazy. Stoics, who would reject the concept of a justified evil, would argue no activity is exempt from moral reasoning, including the conduct of war. Even if war can never be made perfect (that would be peace), it can still be waged in ways more or less destructive depending on the choices made. In other words, the duty of non-maleficence is not a binary feature overridden once and then discarded; rather, it must be overridden continuously, with case-by-case evaluations of every potential violent act, prohibiting those that do not meet the burden of proof.

For example, noncombatants are unequivocally off-limits from direct attack. As unwilling participants in conflict, they are properly regarded as its victims and this burden cannot be overridden by mere suspicions they harbor or sympathize with the enemy. Furthermore, even though I have a role-based duty to preserve the lives of my troops, I cannot do so by clearing population centers with bombers and heavy artillery. Just as my troops cannot attack noncombatants to improve their own safety, I cannot authorize attack of noncombatants for that reason either (Michael Walzer writes eloquently on this in his excellent Just and Unjust Wars). These restrictions reflect the jus in bello principles of discrimination and noncombatant immunity. A distinctly Stoic contribution is the belief noncombatants are not just victims, but are fellow citizens of a higher, global community.

Broadly understood as Stoic cosmopolitanism, this belief illuminates the space between traditional jus in bello criteria and practical realities, where questions of immense moral consequence can arise. For example, even if I am not permitted to kill noncombatants to save my own troops, might I reduce their margin to safety? Can I make them uncomfortable or miserable? Can I starve them or destroy their access to power, water, and medical care? How confident must I be that my actions do not result in their deaths, now or in the future?

It is not uncommon for two lawful and professionally competent commanders to reach different conclusions about what degree of hazard or misery for noncombatants can be justified in the interest of efficiency, mission effectiveness, or safety of one’s own forces. It is precisely in these ambiguous trade spaces that moral wisdom—to include a cosmopolitan ethic—manifests with enormous consequence. Although certain special obligations do distinguish kin and fellow citizens from foreigners, these are generally functions of specific roles and, as such, they cannot override those duties attendant to one’s fundamental role as a reasoning human. The result is that, for Stoics, all wars are civil wars, placing noncombatants among those to be protected, even at significant risk to life and mission.

A special category of noncombatant is the defeated enemy, who should be recognized as an ex-combatant when the fighting stops. Even they would be regarded by Stoics as human beings apart from their roles as combatants, and fellow countrymen in a civil war. Naturally, humane treatment of the vanquished emerges as a separate jus in bello criterion. Once again, Cicero presages the theorists: “Consideration should also be shown to those who have been subdued by force, and men who lay down their arms and seek the sanctuary of our generals’ discretion should be granted access to them, even if a battering ram has shattered their city wall” (On Duties 1.35). He refers to Julius Caesar’s promise not to destroy a besieged city if surrender came before the battering ram was applied, which it regrettably did not.

For any act of violence, a thoughtful assessment of its costs against the proposed tactical, operational, or strategic benefit is required. These include the second- and third-order effects that may transpire over generations. If a specific use of force is not essential to achieving legitimate military objectives aligned with the broader moral goals of the war, then the act lacks necessity and fails to override the duty of non-maleficence. I cannot kill or destroy simply because I am in enemy territory or because my target may be an enemy combatant—the killing must serve a valid military purpose. Moreover, the military gain must be worth the human suffering it causes; otherwise, the jus in bello criterion of proportionality will not be satisfied.

In summary, I have addressed the question of whether Stoics can justifiably perform acts of violence by applying concepts of competing and overridden moral duties. I concluded they can—and, indeed, sometimes must—provided the appropriate criteria are satisfied, as outlined above. However, it is important to note this article has not considered the matter of collective action and whether participation in such actions might constitute a forfeiture of moral freedom. If it does, this would render such actions incompatible with Stoic principles. I address this topic at length in the book, but that is well beyond the scope of this article. Suffice it to say, I conclude that collective action, including military action, does not constitute a surrender of moral freedom to one who fully apprehends their faculty of moral choice.

About the Author

Commander William C. Spears is a submarine warfare officer in the United States Navy and author of Stoicism as a Warrior Philosophy: Insights on the Morality of Military Service. All opinions expressed in this article are his alone and do not constitute an official position of the United States Government or any government organization.