What Does Catholic Just-War Doctrine Say About Israel and Hamas?

REGISTER ROUNDTABLE: V. Bradley Lewis, Daniel Philpott and R.R. Reno Assess How Church Teaching Applies to the Crisis in the Holy Land

A picture taken Oct. 23 from the southern Israeli city of Sderot shows smoke and debris ascending over the northern Gaza Strip following an Israeli strike, amid the ongoing battles between Israel and the Palestinian group Hamas. Thousands of people, both Israeli and Palestinian, have died since Oct. 7, after Gaza-based Palestinian Hamas militants entered southern Israel in a surprise attack, leading Israel to declare war on Hamas on Oct. 8.
A picture taken Oct. 23 from the southern Israeli city of Sderot shows smoke and debris ascending over the northern Gaza Strip following an Israeli strike, amid the ongoing battles between Israel and the Palestinian group Hamas. Thousands of people, both Israeli and Palestinian, have died since Oct. 7, after Gaza-based Palestinian Hamas militants entered southern Israel in a surprise attack, leading Israel to declare war on Hamas on Oct. 8. (photo: Jack Guez / AFP via Getty Images)

The Oct. 7 atrocities committed against Israeli citizens by Hamas militants provoked an intense retaliatory military operation inside the densely populated Palestinian territory of Gaza. 

In the context of this devastating Israel-Hamas war — which as of early November has resulted in the deaths of more than 1,400 Israelis and upwards of 10,000 Palestinians, according to the Hamas-run Ministry of Health — the Register asked three leading Catholic analysts to weigh in regarding the application of Church teachings regarding war and conflict. 

V. Bradley Lewis is an associate professor of philosophy at The Catholic University of America. He is currently working on a book project provisionally titled The Common Good and the Modern State

Daniel Philpott is a professor of political science at the University of Notre Dame and author of Just and Unjust Peace: An Ethic of Political Reconciliation. He is currently working on a book exploring the Christian concept of justice.

R.R. Reno is the editor of First Things. Previously a professor of theology and ethics at Creighton University, he is the author of several books, including Return of the Strong Gods: Populism, Nationalism and the Future of the West.


The Second Vatican Council’s pastoral constitution on the Church in the modern world, Gaudium et Spes, recognizes the moral legitimacy of a country defending its national sovereignty. Does this teaching, which arises from the Church’s long-established just-war doctrine, support Israel’s decision to “eradicate” Hamas — designated by the U.S. to be a terrorist organization — through airstrikes and a ground invasion following Hamas’ brutal Oct. 7 attack that killed more than 1,400 people and kidnapped more than 200?

LEWIS: Israel has a right and an obligation to protect its citizens. Hamas’ Oct. 7 attack on Israel was without justification and carried out in a way that completely flouted the laws and norms of armed conflict. Its leaders have already said that, given the opportunity, they would repeat these atrocities, and its governing documents commit it to the total destruction of Israel. Under such circumstances, no government would tolerate the continued presence of a group like Hamas on its border. So long as Hamas continues to exist as an effective terrorist organization, operating under color of government authority, it constitutes a mortal threat to the people of Israel. Moreover, it constitutes also a mortal threat to the Palestinians living in Gaza, whom it has ruled tyrannically, and now callously uses as shields.

PHILPOTT: Under the Catholic Church’s just-war ethic and international law, Hamas’ attack of Oct. 7 was the quintessential crime. It was the crime of aggression, a crime against humanity, and a pogrom against Jews on a scale unseen since the Holocaust. Terrorism has long been a “weapon of the weak,” but no grievance justifies such an attack, which is intrinsically evil. Hamas’ charter commits it to destroy Israel, it has attacked Israel many times before, and it has continued to fire rockets at Israeli cities since Oct. 7. Israel has a right — and a duty — to defeat Hamas as an act of self-defense, and this defeat justifiably includes the dismantling of Hamas. The just-war ethic rules out a war of retribution — though Israel would be right to send Hamas leaders to an international tribunal — and all the more so a war of revenge, bringing into question Prime Minister Benjamin Netanyahu’s call for “mighty vengeance” and Israeli top officials’ references to Gazans as “human animals.” 

RENO: I take the term “eradicate” to mean the elimination of the capacity of Hamas to mount attacks. This strikes me as a morally sound objective. The Oct. 7 Hamas attack makes it impossible to doubt the ongoing intent of Hamas leaders to strike again and kill as many civilians as possible. Therefore, the duty to protect innocent life, one of the fundamental principles of statecraft, requires depriving Hamas of the capacity to undertake terrorist operations in the future.

There is no formula to determine when this goal is achieved. Hamas enjoys popular support among Palestinians. Its militia is not in uniform and mixed with the general population. Given these challenges, a significant and intensive military intervention may be judged proportionate. However, the Israeli government will need to maintain moral discipline to stay focused on the political-military goal of destroying the war-making capacity of Hamas.


The Israel Defense Forces (IDF) have bombarded Hamas military operations embedded in Gaza’s urban neighborhoods, and significant civilian casualties have resulted. Israel says it tries to protect noncombatants, while Hamas appears to use civilians as human shields. Hamas has also made clear its goal is the “complete destruction of Israel.” How should Israel balance the right to defend itself with the duty to minimize civilian casualties in the current context?

LEWIS: The moral principles governing armed conflict strictly prohibit the targeting of noncombatants. Those principles also hold that unintended harm to noncombatants — and such harm always occurs in war — must not be disproportionate. This involves fine judgments by political leaders, military commanders and legal advisers, who must translate a general rule into particular rules of engagement that guide combatants. There is no formula here, but rather judgments about military necessity and predictions about concomitant harms. The conditions that exist in Gaza are particularly challenging in this respect, given its size and population density. There must be a serious commitment to minimize civilian casualties, but the balance struck is a function of intelligence about the location and value of enemy targets and information about noncombatants that only the decision-makers have.

PHILPOTT: The just-war ethic demands that war aim at military targets and holds that the foreseeable concomitant deaths of civilians are permissible, though tragic, though they must be proportionate to the value of the military target. Proportionality, though, is difficult to assess. Thus far, more than 9,400 civilians have died in Gaza. Hamas has a long history of placing its fighters adjacent to hospitals, schools and homes, making discrimination difficult and perhaps even courting the deaths of civilians in order to garner popular support for its cause in the Middle East. I have seen no evidence that Israel is targeting civilians directly, and its targeting policies are under civilian oversight. Still, Israel has a responsibility to achieve its aims in a manner that minimalizes civilian deaths, raising questions about the justice of its blockade of Gaza, its bombing at a refugee camp, and its disallowance of more time for civilians to evacuate northern Gaza. These policies also hurt Israel politically and diplomatically, a crucial factor for its military success and its long-term interests in peace and security.

RENO: The principle of double effect is important in this context. The first element of this principle concerns intention. Hamas (and other terrorist organizations) openly state their intention to kill civilians. Israeli officials have repeatedly stated the opposite.

However, what one intends is not always what happens. In urban warfare, especially against an adversary that has no uniforms and operates within the general population, the IDF generals, whatever their intentions, foresee that innocent civilians will be killed. This does not mean that the IDF cannot conduct offensive operations. But it does impose a duty to use force in ways that minimize civilian casualties.

At this juncture, the IDF is fulfilling this duty. Unlike Hamas, which launches rockets that target Israel’s general population, Israel is not indiscriminately bombing Gaza. 

A just war requires proportionate use of force. But the “proportion” concerns the degree of violence in relation to the military goal (which must also be just), not body counts on one side or the other. Hamas attacked in such a way that it clearly revealed that its talk of “cleansing” Israel of Jews is not just rhetoric. In these circumstances, Israeli leaders must disarm Hamas, and given their tactics of using their own population as human shields, many more civilians are likely to be killed. This is something we should grieve over, but it is not the result of injustices committed by Israel.


Israeli soldiers and civilians left Gaza in 2005, and Hamas ultimately took control of the enclave in 2007. Since then, Hamas has launched rockets periodically and indiscriminately at Israel. No elections have been held since 2006, and Gaza inhabitants have suffered from Hamas’ authoritarian rule as well as Israel’s economic blockade and occasional military incursions. More recently, Israeli Prime Minister Netanyahu adopted divisive policies that stoked Palestinian resentment and diverted attention from the country’s national-security concerns. Does Catholic social teaching ask national leaders to consider the responsibility they may bear in contributing to the conditions for conflict?

LEWIS: The normative principle governing all political decisions is that of the common good of the community (Catechism of the Catholic Church, 1903), not simply the good of one’s own political party or coalition. Imprudent political decisions can certainly contribute to conditions that make conflict and war more likely, and political leaders must be accountable for their decisions, accountable to the people through normal legal and political channels. At the same time, the atrocities committed by Hamas cannot be justified by any circumstances or intentions. The people of Israel will need to make some important decisions about their political future once the immediate crisis has passed, and this will include decisions about Israel’s relationship with the Palestinians, whose common good must also be taken into account. But Hamas and Hamas alone are responsible for the enormities of Oct. 7.

PHILPOTT: Hamas has a long history of aggression and authoritarian rule that confirms the reality, not the paranoia, of Israel’s fears about its security. For its part, though, Netanyahu’s government has promoted settlements on the West Bank forwardly, not defensively, and has treated Palestinians harshly and undermined prospects for a stable peace. The greatest lesson of all of these grievances is the urgency of a two-state solution. Talk of peace may seem absurd as rockets fly and deaths mount. And, to be sure, the Palestinian leadership rejected this solution at least twice. Sometimes in history, though, upheavals create fresh conditions of possibility: Perhaps the downfall of Netanyahu’s government, the defeat of Hamas and the discrediting of its allies, and a heightened weariness of war and interest in a lasting settlement on both sides might yet spark a deal. We cannot foretell these or other eventualities, but neither did many predict the Abrahamic Accords between Israel and other Middle Eastern states that arose virtually yesterday. The virtue of hope is indispensable.

RENO: Leaders certainly bear responsibility, not just for allowing conflict to simmer (or even stoking it), but also for negligence in defending one’s own people.

However, when attacked, the first duty of a leader is to defend his people and defeat their adversary. After that goal is achieved, Netanyahu and other Israeli leaders need to consider their own contributions to the conditions leading to the conflict and they should approach peace-making accordingly, hopefully making Palestinian-Israeli tensions less explosive.

Put simply: Every conflict explodes into violence for many reasons. In a fallen world, there are no immaculate players in the political drama. But moral common sense recognizes that the burden of guilt falls on those who break the peace, however imperfect, with acts of violence that target innocent people. 


Finally, the U.S. government has endorsed Israel’s right to defend its sovereignty, but also has urged the IDF to adopt a proportionate response to Hamas’ ongoing aggression that does everything possible to protect civilians and allow for the flow of humanitarian aid. What should be Washington’s moral priorities as Israel’s most powerful ally? 

LEWIS: The U.S.’ first priority should be to see that Israel is able to defend itself and to do so in a way that is morally responsible. It must also act diplomatically — and diplomacy includes the movement of military assets — to prevent a wider conflict from breaking out in the region. A wider war would benefit only the terrorists. Last, but by no means least, the U.S. should do what it can to aid the innocent civilians in Gaza and to promote a future there that is peaceful. These are both political and moral priorities. Some will ask why the U.S. should have these responsibilities, given the serious domestic challenges we face. The answer is that, given our wealth, influence and power, we are the only nation that can likely affect these things. Our wealth and power are blessings, but also the source of obligations, just as they would be for individuals. 

PHILPOTT: Yes, pressing Israel to do more to limit civilian casualties and allow humanitarian aid ought to be one of the United States’ top priorities. Deterring other powers from aiding Hamas and Hezbollah is another goal. Following the end of the fighting, the U.S. ought to work to lay the groundwork for peace. The U.S. can coordinate and contribute to relief and rebuilding efforts. It can conduct diplomacy to encourage Middle Eastern governments to support the rebuilding of a post-Hamas Gaza and perhaps even to form a joint provisional government for a temporary period. The U.S. can also press both sides towards a two-state solution, a far-from-perfect but by far the most viable formula for a lasting settlement.

RENO: Washington’s overriding moral duty is to shore up deterrence. As the leading global military power, the U.S. must sustain the credible threat of decisive military response in order to deter state-sponsored militias and terrorists from killing innocent people. For this reason, it is morally imperative to support Israel’s goal of eliminating Hamas, or at least to so degrade its operational capacity that other bad actors in the region (and around the globe) will think twice before launching assaults.

Iran stands behind Hamas, as well as other regional militias. Russia plays a role as well. The Biden administration seeks to avoid escalation. That’s the correct judgment, in my opinion. But they need to be deterred from fomenting more conflict. A proportionate but comprehensive military operation in Gaza by Israel, with unequivocal American support, will renew the atmosphere of deterrence, which is the only way to maintain peace in that region of the world.