Just War Theory and the Philosophers of Gaza

Philosophers have long tried to develop clear moral principles to govern the conduct of warfare. Here's why they're engaged in a fierce debate over Gaza.

“Justice” by Joseph Binder (1957).

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There are some moral horrors so great—babies starving to death within miles of abundant food, children shot by snipers, or tortured, emaciated hostages tucked away in dark tunnels like caged animals—that it is akin to staring directly into the sun.

The war in Gaza is a moral horror, a scar on humanity. However, unlike most other moral horrors, this is a polarizing one. People draw radically different conclusions about the ethics and justice of the ongoing conflict.

While polling in recent days suggests there has been a sharp decline in US public support for Israel’s actions in the war, with stark party-line divides, debate about the conflict has been remarkably shallow and predictable.

Politics is the art of preventing avoidable harm. And yet, those most outspoken in this conflict’s politics are not pragmatists but extreme zealots, unwilling to concede even an inch of moral ground. They often deny the humanity of their enemies, with emotive passion in abundance while discussion of underlying principles is too often lacking.

Meanwhile, as children starve and people get shot while trying to secure food, most people simply recoil from the scale of human tragedy, particularly from the relentless daily death tolls racking up in Gaza. One can be unsure of how to grapple with the moral complexities and the tangled history that strangles discussion of the conflict, but still feel certain that the killing, the suffering, the avoidable cataclysm must end.

Part of the explanation for the shallowness of debate lies in moral conflation. Some peddle the obviously false notion that anyone who criticizes the Israeli government for inflicting tens of thousands of civilian deaths or blocking food to a starving population is an anti-Semitic supporter of Hamas.

Others insist that expressing outrage at October 7th, or concern for innocent hostages, or saying that civilians should not be targeted by rockets in their homes is somehow endorsing Netanyahu’s government and negating the collective suffering of millions. Moral conflation is the bastard offspring of lazy ethics, derived from an inability to articulate clear dividing lines and principles on which to base our viewpoints.

Meanwhile, outside of public view, philosophers of warfare are engaged in a fiery debate about the ethics of killing in Gaza. These rigorous, thoughtful arguments are, alas, tucked away in esoteric philosophy journals with names like Analyse und Kritik. That is a shame, because the frameworks that philosophers use to evaluate the moral justifications of warfare offer us a firmer intellectual scaffolding within which we can build better arguments—and perhaps allow us to persuade, rather the verbally bludgeon, those who see the world differently.

My task here, then, is not to catalogue the moral outrages; those are in plentiful, depressing supply. Nor is it to definitively proclaim The Truth about a conflict that routinely causes decent, moral people to arrive at opposite ethical conclusions. Rather, my aim is to articulate the sharp philosophical dividing lines that allow anyone to determine whether a given war is just—and if it’s not, why, precisely, it violates those moral principles.

In turn, clearer frameworks can elevate public debate—and make political pressure more targeted at the specific objections to an unjust war. ,

I: The origins of just war theory

Before we return to Gaza, though, we need to first understand the core ideas embedded in the philosophy of warfare.

The problem of ethics in combat has preoccupied thinkers for as long as humans have been killing one another in systematic combat. There is evidence of early incarnations of just war principles as far back as ancient Egypt, though it was largely assumed that the Pharaoh’s fighting would, by definition, be just. Ancient Hindu texts prohibit the use of barbed or poisonous weapons and specifically outlaw the use of violence against those who are weak, elderly, or have given up on the battlefield.

In the West, philosophers from Augustine to Aquinas have long argued about what makes wars just, but one of the most influential premodern thinkers on the topic was the Dutch jurist Hugo Grotius. His 1625 work, De jure belli ac pacis, or On the Law of War and Peace, furthered one of the most important distinctions in what would later become called just war theory: the separation between just causes for wars and just conduct during war.

In the modern era, the canonical development of that separation was articulated by Michael Walzer, one of the pre-eminent living philosophers of warfare, who taught since the early 1960s at Harvard and Princeton. Walzer’s 1977 book, Just and Unjust Wars, remains the standard starting point for understanding just war theory.¹

Walzer, like many classical just war theorists before and since, argues that it is essential to differentiate between jus ad bellum (right to war) and jus in bello (justice in war).

These concepts are easy to illustrate with clear-cut historical examples that have obvious good guys and bad guys. According to this classical formulation, it is possible to have a split verdict: the Nazis never had a just cause for war, but it would be possible for an individual Nazi soldier to follow the rules of war and avoid committing war crimes.

On the flip side, the Allies were fighting a just war against the Nazis, but the firebombing of Dresden was a violation of just war principles. Similarly, one could, for example, believe that Israel had a right to defend itself after Hamas’s October 7th attacks (jus ad bellum) but still argue that its execution of the war and the resultant deaths of tens of thousands of innocent civilians and ongoing food scarcity have violated the rules of warfare (jus in bello).

While definitions vary, some of the key principles that are widely agreed to give a country the right to war are:

Just Cause: Wars may only be legitimately started for certain reasons. An act of aggression intended to seize territory is unacceptable, whereas responding to aggression in self-defense, protecting innocent civilians in imminent danger, and so on, are frequently cited as examples of just causes. As we’ll return to later in evaluating Israel, intent matters.

Last Resort: In an ideal world, wars would only be started after all alternative diplomatic and non-violent pathways are exhausted. Additionally, warfare is not a binary—war or not war. Instead, there are near-infinite varieties of types of warfare, and the principle of last resort suggests that warfare would be most just if it only escalated over time after less drastic attacks were tried rather than going straight to, say, nuclear bombs.

Probability of Success: It is considered unjust to start a war that has zero chance of achieving the just cause. In theory, if you knew with certainty that an act of state violence would achieve nothing, it wouldn’t be permissible to kill people in pursuit of that fool’s errand. (This criterion is philosophically interesting and intersects with my research—particularly that on risk, uncertainty, chance, and chaos theory—because forecasting during the march to war is often the lovechild of wishful thinking and divination.)

Once a war has begun, according to classical Just War Theory, the focus shifts to jus in bello, or justice in war. Specifically, combatants must follow these principles:

Discrimination: Extensive efforts must be made to discriminate between combatants and non-combatants in order to avoid killing non-combatants.² (Philosophers of war accept that some innocent civilians will inevitably get killed in warfare, but the principle refers to both intent and probability estimates of civilian deaths).

Military Necessity: Any attack must have a legitimate target and a legitimate military objective that is essential to achieve the just aims of the war. If the same goal can be reached with less violence or destruction or through another comparable means, then the military action would be unjustified.

Proportionality: This is one of the trickiest principles to pin down, but the idea is that one should not engage in violence that creates disproportionate harm relative to achieving a legitimate military objective. For example, most would agree that blowing up an apartment block to kill a rank-and-file enemy soldier would be disproportionate, as would using nuclear weapons in almost every scenario imaginable.

No Means Mala in Se (Evil in Themselves): While moral philosophers rarely make absolutist claims, most agree there should be a much stronger principle against particularly objectionable tactics, such as mass rape, ethnic cleansing, depraved treachery (such as disguising combatants as Red Cross personnel), mass starvation of civilians, and using weapons that cannot be controlled once they are deployed (such as biological pathogens).

At the International Committee of the Red Cross headquarters in Geneva, the outgrowth of these principles is printed on glass: “Even wars have rules.”

Photo credit: BBC News.

II: Are combatants on both sides morally equal?

The separation of the two concepts—right to war and justice in war—allows for the possibility that just wars can be fought unjustly, or that unjust wars can be fought ethically. Crucially, that divide yields a bedrock principle of Walzer’s classical just war theory (and international humanitarian laws governing warfare) called the Moral Equality of Combatants.

By splitting the decision to go to war from those who fight in it, it becomes possible to extend equal legal rights to soldiers on both sides of a conflict, no matter how vile their side’s aims may be—so long as they behave according to the laws of war.

According to this principle, it doesn’t matter whether Russia was in the wrong when it invaded Ukraine: Russian soldiers and Ukrainian soldiers are still treated equally under the laws of war. It’s therefore permissible for anyone in that war to shoot at combatants from the other side. Put bluntly, if two soldiers are in Eastern Ukraine—one Ukrainian, one Russian—both are equally allowed to kill the other. After all, in that moment, they are both trying to kill someone who is trying to kill them.

This separation makes some intuitive sense, particularly because some soldiers are not willing participants in warfare, or they’ve been brainwashed by propaganda, or were forcibly coerced to wear the uniform.

When I visited the Nazi cemetery in Normandy, and walked through row after row of gravestones for 17 and 18 year-old boys, I saw them also as victims of the Nazi regime. And I thought to myself: what would any teenager do if they were shipped off to Normandy, placed on the coastline, and then 156,000 soldiers landed and started shooting at them? The same conflicted thoughts coursed through my mind when I attended a war crimes trial at The Hague, of a heinous Ugandan warlord who became a monster only after he was forcibly abducted as a child and then forced to murder civilians. Perpetrators and victims.

These are the moral complexities that regularly upend our desire for clear-cut assessments of wartime ethics.

But there’s also something unsatisfying and unsettling about the existing convention that always treats combatants as legal equals. After all, if a bank robber goes into a bank and comes across a police officer in the process, the robber is not justified in shooting the officer even if the officer is about to shoot him. The bank robber does not have the right to self-defense.

In that context, it’s obvious that the moral condemnation applies to the robber, not the police officer. The aggressor is to be condemned, and those condemnations don’t stop simply because both may be trying to kill each other in the moment. The context of how the confrontation began matters enormously to our judgments about it. Shouldn’t that be true for war too?³

According to Walzer, though, these intuitions need not apply to soldiers because warfare is morally unique. “Their war is not their crime,” he argues, “for the war itself...soldiers are not responsible.”

This argument is crucial to understand when evaluating wars, because individual acts carried out by combatants may not reflect underlying intentions of leaders and generals. If there is a separation of moral responsibility between soldiers and politicians, it cuts both ways. Soldiers may not be responsible for the president’s march to war, but presidents can also disavow the actions of soldiers. That makes it easier to dismiss a child getting shot in the head as an accident—or a rogue bad apple—rather than a deliberate strategy.

Is it Israel’s fault if the military doesn’t deliberately target civilians, but nonetheless orders an airstrike on a target knowing that it’s likely to lead to dozens, possibly hundreds, of civilian casualties? How many accidental deaths reveal an underlying strategy—or an unacceptable risk tolerance for killing civilians?

III: The philosopher’s war

Walking through medieval cobblestone streets to Corpus Christi College at the University of Oxford, I’m passed by a man on a bicycle with a fluorescent yellow hi-vis vest, a robust mane of slightly unruly grey hair jutting out below his helmet. I recognize him immediately as the man I’ve come to see: Professor Jeff McMahan, one of the world’s leading philosophers of warfare.

Professor Jeff McMahan. Photo Credit: John Cairns.

McMahan, who has courted controversy at various points throughout his career in applied philosophy, managed to squeeze me into his day’s schedule between grandparenting duties of reading Dr. Seuss and drawing pictures.

Officially retired, McMahan says he’s busier than ever. And that’s no surprise: much of his life’s work has been to grapple with moral conundrums kicked up by warfare and killing—and between Ukraine and Gaza, many of the philosophical hypotheticals have become chillingly real. He’s churning out essays and research articles while fielding requests for podcasts, hoping to better inform the public of the moral stakes in these two atrocious conflicts.

McMahan, since 1994, helped launch a major challenge to classical Just War Theory, resulting in a schism with Walzer over whether a war with unjust aims can ever be executed in a just manner (to simplify: Walzer says yes, McMahan says no).⁴

Today, the two philosophers also have radically different evaluations of Israel’s conduct in Gaza nearly two decades later. Walzer, now 90 years-old, has emerged as a prominent supporter of Israel’s war in Gaza, albeit with some minor critiques of tactics.

McMahan, by contrast, forcefully argues that Israel is currently engaged in an immoral and unjust war because of the disproportionate harm inflicted on civilians. (McMahan has, over the years, written scathing criticisms of Israeli government policy over Palestinian civilian death tolls but has also been shouted down before an invited lecture in Beirut for being a “Zionist” because of “an unpaid advisory affiliation with the Hebrew University in Jerusalem”).

Some topics do not tend to divide philosophers of war. For example, most agree that Israel has a right to defend itself and that any nation attacked as it was on October 7th would be justified in responding with some level of force.

Most would also agree that Palestinian children living in Gaza are victims of horrific injustice, not only because of the atrocious and relentless tragedies of the war, but because of their confined lives, living in a place where nobody would rationally choose to live, under occupation and governed by a murderous terrorist organization.

Most philosophers of war also argue that Hamas is a despicable, monstrous organization with genocidal hatred and grotesquely anti-Semitic rhetoric stitched into its founding manifesto and war crimes embedded in its formally stated political aspirations.

Most also take it for granted that because Hamas deliberately targeted civilians on October 7th, it was an indefensible act of mass murder that clearly meets the textbook definition of terrorism. Despite legitimate grievances from Palestinian civilians, there is a consensus that Hamas’s October 7th attack was obviously unjust, deeply immoral, and depraved.⁵ (McMahan’s phrasing to me was that Hamas are “a group of thugs, they’re terrorists, they're murderers”). There is no legitimate debate about whether they should release the hostages—the answer is clearly yes.

The crux of the dispute, then, is over this question: Has Israel’s response to the October 7th attacks fulfilled the conditions to be considered a “just war”?

IV: Human shields, proportionality, and starvation

Philosophers who endorse Israel’s conduct in the war since October 7th, 2023 tend to argue that high numbers of civilian deaths are permissible for two main reasons.

First, they argue, Israel is morally absolved from the killings because it does not deliberately target civilians. As the Swedish philosopher Per Bauhn insists, Israel:

“has taken every reasonable precaution to minimise non-combatant casualties in Gaza…These measures involve the use of precision guided munitions (PGMs), the collection of pre-strike intelligence on the presence of civilians by means of satellite imagery as well as by scanning of mobile phone presence, and pre-strike warnings that actually involve an increased risk of a failed attack as it also alerts the Hamas enemy who is the intended target.”

Second, Hamas’s actions—particularly its efforts to cloak itself among the civilian population, using innocents as human shields, and squirrelling its fighters away in deep tunnels under civilian buildings—mean that the deaths of any civilians during the war should be blamed exclusively on Hamas, not Israel.

Bauhn wrote a scholarly article to that effect, and Walzer seems to broadly agree in an essay he wrote for Quillette:

Deliberately putting the entire civilian population in harm’s way is a military and political strategy. It is designed to make it impossible for the enemy to fight without killing civilians…Every dead civilian is a political asset for Hamas, and this probably accounts for its failure to build civilian shelters (in contrast to the tunnels that protect only fighters).

Similarly, the ongoing crisis—of a starving population, complete with chilling photos of emaciated young children—is said to be the exclusive fault of Hamas because of the risk that they will steal aid and sell it as a means to sustain their violence. If Hamas didn’t do this, they argue, nobody would starve.

Walzer goes on to outright reject the notion of proportionality as a constraining factor in Israel’s war, which is quite a radical position: “In a time of war,” Walzer says, “everybody makes proportionality arguments. But proportionality is a fool’s game, more suited to propaganda than to reasoned judgement.”

Daniel Statman, a philosopher at the University of Haifa in Israel, seems to agree, arguing that because philosophers can never agree on questions of proportionality, perhaps it would be best to avoid the metric altogether: “the fact that many experts reach radically different conclusions about whether an attack on an enemy headquarters is proportionate should prompt caution, maybe even abstaining from judgment in this area.”

Each of these arguments has some merit—much of what they say is factually true—but they are philosophically weak justifications for the ongoing devastation. McMahan (alongside other philosophers who criticize Israel’s ongoing actions in Gaza as disproportionate) is right to challenge them.

McMahan’s core argument is not that Israel had no right to respond to October 7th (Israel clearly did), but that it had a nearly infinite array of options as to which type of war it would execute. He thinks Israel mistakenly and unjustly took the excessive force option that would inevitably result in mass civilian casualties. Or, as he put it to me: “There are indefinitely many ways in which a war can be fought and what Israel under Netanyahu opted for was total war, unrestrained, maximum war.”

That choice, McMahan contends, has provoked enormous backlash and galvanized future extremism, meaning that “the war that Israel has fought has not been the morally best means of achieving Israel’s just cause.”

Moreover, McMahan—and others—reject the moral logic of laying exclusive moral blame for civilian casualties on Hamas even if Israel does not intend to directly kill civilians and even if Hamas uses human shields. The depravity of an enemy, they argue, does not absolve one of all moral responsibility.

But there is a crucial difference between not intending to kill civilians and intending not to kill civilians.

McMahan asks us to imagine a murderer who surrounds himself with 50 innocent bystanders in such a way that the only way to kill the murderer would be to kill those 50 civilians. The murderer, quite clearly, is ultimately to blame for the situation.

But if the police do a risk assessment, conclude that there’s a reasonable possibility that their actions will lead to the deaths of 50 civilians, and proceed anyway—even while taking some laudable precautions to protect the innocents—they are still morally responsible and blameworthy for those 50 deaths. It would be disproportionate to proceed, and the police would still be executing a moral wrong.

More flippantly, if a fly lands on your head, and instead of reaching for a fly swatter, I reach for a gun and shoot the fly, my intent may have been to kill the fly, but I ought to have known that the likely outcome was also to kill you. In short, proportionality matters; even if philosophers can’t agree on a single standard, avoiding foreseeable and disproportionate harm is a central concern for any just war.

McMahan notes, in passing, that the size of the Gaza strip—and its extreme population density—makes it virtually inevitable that any military force such as Hamas will be embedded among civilians. (This is true, but it does not absolve Hamas, and the organization has clearly and repeatedly exploited civilian populations for its military objectives. Similarly, it cuts both ways—the population density also makes it extremely difficult for Israel to avoid civilian harm).

The Gaza Strip, superimposed over Manhattan, for scale.

Regardless, while death tolls are hotly disputed and remain murky, the statistics produced by the Hamas-run Health Ministry in Gaza are actually lower than counts made by independent researchers that were recently published in Nature. That death count, which only extends through January 2025 and doesn’t include casualties from the last six months, suggests that 84,000 people had been killed in Gaza since Hamas’s attack on October 7th, 2023 that triggered the war.

Relatedly, Doctors Without Borders has been tracking its Palestinian workers and their families since the start of the war. According to their recent data, which may not perfectly extrapolate out to the entire population but offers a useful snapshot, two percent of the people in their sample have died and seven percent have been injured. Moreover, within the sample, 48 percent of the people who have died from blast injuries were children, with the overwhelming majority of those deaths being in children under the age of ten. These statistics, like any data coming from Gaza, are partially flawed, but what’s unequivocally clear is this: the scale of civilian death is staggering.

That terrible toll undercuts any attempt to claim that these are all unintended accidents, or the unobjectionable, humdrum byproducts of war. The first few times, perhaps, one can claim surprise. But after nearly two years, it’s part of a strategy that factors in those deaths as part of an explicit calculation.

“I accept that it is morally worse if innocent people are killed intentionally than if they are killed foreseeably but unintentionally,” McMahan writes. “But the number of innocent people who are killed matters at least as much as what is in the killer’s mind.” Most estimates place the number of children killed well above 10,000, and whether intended or not, their deaths matter.

There are, it’s worth noting, also good reasons to question Netanyahu’s government in its stated calculations on two just war principles: proportionality and discrimination between combatants and civilians.

First, since the beginning of the conflict, there have been many statements made—including by senior officials in the government—that there are “no innocent” civilians in Gaza. Nissim Vaturi, the deputy speaker of the Knesset, Israel’s legislature, put it bluntly: “It is better to burn down buildings rather than have soldiers harmed. There are no innocents there.” President Isaac Herzog put it like this: “It’s an entire nation out there that is responsible.”

This notion, as the philosopher Tony Coady writes, “is basically a version of the discredited plea of the ‘collective guilt’ of whole nations or communities” that has frequently been used in history to justify atrocities. (Hamas, it’s worth noting, often uses anti-Semitic statements of collective guilt and has repeatedly called to eliminate the entire state of Israel.)

The above arguments about complicit Palestinian civilians are not completely baseless—some significant number of civilians in Gaza obviously provide material support to Hamas fighters—but collective guilt is nonetheless antithetical to moral principles, not least because nearly half of Gaza’s population are children. (Even then, Vaturi, deputy speaker of the Knesset, coldly claimed that every child born in Gaza is “already a terrorist, from the moment of his birth.”)

Second, explicit proportionality calculations that have leaked seem excessive. One report that draws on leaks from Israeli targeting officials claims that they were told that they could authorize attacks, including on low-level targets, even if they were likely to kill between 15 and 20 civilians. As The Guardian reported: “Attacks on such targets were typically carried out using unguided munitions known as ‘dumb bombs’, the sources said, destroying entire homes and killing all their occupants.”

Third, there is some evidence—reported in both The New York Times and in Israel’s +972 Magazine—that Israel is using some “double tap” attacks, in which a secondary strike kills rescue workers who might otherwise help save the life of a military target who was wounded in the first explosion. (Such secondary attacks would violate the discrimination clause of just war theory).

Finally, civilians are beginning to starve to death. Some argue that Hamas is ultimately to blame in the broader sense, both for starting the war with its terrorist attack and for abusing aid supplies. But even New York Times columnist David French—who describes himself as a conservative and a Christian Zionist—notes that Israel is now responsible for what happens in Gaza today:

“The dominant power in Gaza is Israel, not Hamas, and Israel, not Hamas, is the only entity with both the power to control aid distribution and the ability to obtain and distribute aid in the Gaza Strip. There is no way for Gazans to feed themselves. They are utterly dependent on Israel, and Israel removed the United Nations from the aid distribution network without replacing it with an effective alternative.”

As the scholar Laura K. Graham argues, engineering starvation in war is both unnecessary and disproportionate—and does not fulfill the criterion of discrimination and military necessity in Just War principles. She also argues that it violates the malum in se, or evil in itself, prohibition.

Bizarrely, however, as Graham notes, loopholes allow it in international law: “current instruments permit starvation when it is an indirect consequence of legal methods of warfare, such as sieges and blockades.” It is an indefensible moral blight that hungry civilians are being gunned down as they try to reach scarce food shipments. Those killings don’t only violate principles of justice, but they are also severely damaging Israel’s global reputation—and thereby inadvertently undercutting some of its long-term war aims.

V: End game: intentions in warfare

Presidents and generals are not oracles. Or, as McMahan puts it to me while sipping coffee: “Many world leaders are actually not very intelligent people and are swayed by their biases” so that they often fail to accurately forecast outcomes based on their strategic goals and intentions.

Nonetheless, when we evaluate the morality of an act of war, our task is not to subjectively evaluate what a leader hoped would happen—we can never know for sure what is inside their minds—but instead judge the most likely outcome of that action based on the available evidence. And here, to my mind, lies the nub of the problem with Israel’s enigmatic endgame in Gaza.

Recall that just wars must have both a just cause and a probability of success. The kind of war that Israel is executing in Gaza has directly pitted those two principles against one another, depending on what Netanyahu’s ultimate intentions may be.

Scenario 1: Just Aims, No Chance of Success. If, for example, Netanyahu was hoping to achieve a lasting and just peace, with at least tolerable conditions for Palestinian civilians living in Gaza, while also degrading or destroying Hamas, then the war would have an underlying just cause. However, the chosen war strategy that has been executed would have precisely zero chance of achieving all those goals. Much of the territory is rubble. By January 2025, six out of every ten buildings in Gaza had been damaged or destroyed. That didn’t happen by accident, nor was it unforeseeable.

Scenario 2: Unjust Aims, High Chance of Success. If, by contrast, Netanyahu was hoping to once-and-for-all eliminate the security threat of Hamas by clearing the Gaza Strip of most, or all, Palestinians and relocating them—an objective that would clearly fit the textbook definition of ethnic cleansing—then the war aims would not fulfill the just cause criterion, but would clearly have a high probability of success under the existing military strategy.

Indeed, as the philosopher Daniel Statman correctly notes, the war has likely been an effective deterrent to future violence. He points to an interview with Mousa Abu Marzouk, the head of Hamas’s foreign relations office, who “said that he would not have supported the attack on Israel had he known of the devastation it would wreak on Gaza. It seems plausible to assume that Abu Marzouk is not the only member of Hamas who will think twice before attacking Israel again.”

Current thinking from the Israeli government seems to dovetail with Scenario 2 above. The far-right Finance Minister, Bezalel Smotrich, said that the Gaza Strip is an “inseparable” part of Israel and called for much larger Jewish settlements across the territory. Similarly, reports from The Times of London suggest that Netanyahu is now openly considering “seizing [the] entire Gaza Strip.” It’s unclear what would happen to the two million people who live there.

In recognition of the brutal realities for civilians in Gaza—and the strategic direction being telegraphed by Netanyahu—600 former Israeli security and defense officials, including former heads of intelligence agencies, have written a letter calling for an end to the war.

They argue that the war has morphed from a just one to an unjust one because of the excessive violence after achieving the core military objectives of debilitating Hamas. “At first this war was a just war, a defensive war, but when we achieved all military objectives, this war ceased to be a just war,” noted Ami Ayalon, the former head of Shin Bet, Israel's domestic spy agency.

Criticizing Israel’s tactics, as they have, does not make them anti-Israeli stooges of Hamas. Instead, they are grappling with the principles of proportionality and probability of success when thinking about what is likely to be best for Israel, too.

Regardless of what is morally right, the brutal tactics unfolding before the world’s eyes, with dystopian daily headlines, may profoundly backfire, severely damaging Israel’s international standing for a generation while fanning the flames of extremism. Battlefield destruction does not always yield lasting victory.

Isaac Deutscher, the Polish writer and activist—who personally survived pogroms against Jews and lost family members in the Holocaust—issued a cautionary warning after Israel’s decisive victory in the 1967 war. Deutscher invoked a phrase in German, Man kann sich totsiegen, “you can triumph yourself to death.”

Back in the ornate Oxford college alongside McMahan, I pause to sip my coffee while contemplating the detached abstraction of our discussion. We can debate ethics and conjure up moral hypotheticals while the crushing reality of warfare has brutally ended or irrevocably destroyed the lives of thousands of civilians in Israel and hundreds of thousands in Gaza.

Right now, there are people starving, as fully stocked shelves and convoys of food sit miles away. Right now, there are families of hostages who are trying to somehow push chilling fresh images of their emaciated, skeletal son from their minds so they can somehow get through today.

The ethical debates around the war in Gaza are crushingly difficult, mired in uncertainty, our initial judgments constantly tugged at by those “yeah, but” sentiments that convey the moral complexity of the war. Nonetheless, my discussion with McMahan does not feel like a thought experiment. As we discuss the moral dilemmas of grotesque human tragedy and the avoidable violent deaths of children, I repeatedly see tears in the philosopher’s eyes.

As we shake hands and say goodbye, McMahan dons his helmet and sets off on his bike to return to his grandparenting duties. “I’m going to introduce her to Bugs Bunny for the first time tonight,” he tells me. “But I’ll keep the horrors of this away from her as long as I can.”

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Thank you for reading The Garden of Forking Paths. This was a difficult essay to write, because of the moral complexity, sensitivity of the issues, and sheer scale of human tragedy. In each paragraph, there are unwritten caveats, bits of apprehension about the certainty of my views, unmentioned historical injustices. I recognize that some of you will disagree with my writing—some vehemently so—and if that’s the case, my intent was not to offend you, but to try to grapple with these issues as fairly as I could.

1. Just War Theory has inspired international law but it is not the same. The philosophical debates are about the morality of warfare, which is distinct from currently agreed legality of warfare.

2. In revisionist just war theory, which I explain below, the distinction is between those who are liable to attack and those who are not liable. Most revisionist just war theorists claim that just combatants (soldiers fighting for the “good guys”) are not morally liable to attack while some civilians on the unjust side may be. (For example, some would argue that a civilian scientist who is working to develop an atomic bomb that is to be imminently used against an enemy population becomes a legitimate military target).

3. This is the view of the revisionists, which I explain a few paragraphs below. McMahan uses a version of this hypothetical to make the case that unjust combatants (soldiers fighting in unjust wars) may have protected legal rights under the “equality of combatants” principle but do not have a moral right to self-defense (akin to the bank robber) if their side is in the wrong in the first place.

4. This sparked a divide between so-called “traditionalists” like Walzer and “revisionists” like McMahan.

5. Some philosophers in this field argue that Palestinian civilians had legitimate, longstanding grievances due to their conditions in Gaza that may have entitled them to using violence; McMahan, for his part, believes that mass non-violent resistance would have been far more effective than Hamas’s use of violence in achieving just goals.