Philosophy War
Seth Lazar, Jonathan Parry
  • LAST REVIEWED: 22 February 2018
  • LAST MODIFIED: 22 February 2018
  • DOI: 10.1093/obo/9780195396577-0125


Wars are large-scale armed conflicts between two or more organized groups. The basic problem of warfare is that it involves inflicting death and suffering on people, who, in ordinary circumstances, would have fundamental rights that protect them against being treated in these ways. Of course, everyone recognizes that wars are problematic in other respects: they corrupt and destroy institutions and relationships, they waste vast sums of wealth that could be used to remedy entrenched vulnerability, and they cause irreversible and massive damage to the natural environment. These are by no means negligible costs. And yet when considering the ethics of war, most start with the killing and the suffering, because if the killing cannot be justified, then the rest is irrelevant: our only choice is to affirm pacifism. However, justifying the killing is a necessary, but not a sufficient condition of justifying wars as a whole. There remain important questions to be asked about how and why the killing may be done. While the permissibility of killing per se provides the philosophical foundations of any theory of just war, the superstructure requires attention to specific questions governing the practice of warfare. In particular, for what reasons may conflict be permissibly initiated? How can we fight permissibly? How can we end wars, and deal with their aftermath, permissibly? The first two—justified resort and justified conduct—correspond to jus ad bellum and jus in bello in historical just war theory. The third is a more novel, less-discussed contribution, coined as jus post bellum by recent scholars. Only a war in which the killing is justified, and which is started, fought, and ended justifiably, can properly be called a just war.

General Overviews

Just and Unjust Wars (Walzer 2006) made an indelible mark on the debate, with which all subsequent scholarship has engaged. Walzer contextualized and synthesized the judgments embodied in international law and the profession of soldiery, and tried to ground them in a theory of individual rights. This last move has invited the most criticism. Some think war cannot be rendered consistent with individual rights and thus advocate pacifism (Holmes 1989). Others think that just war theory can be defended, but there is a huge difference between that theory and the underpinnings of international law. McMahan 2009 and Rodin 2002 are the most sophisticated statements of these positions, while Coady 2008 defends similar conclusions in a more accessible style. Ramsey 2002 is an interesting 20th-century counterpoint to Walzer, his theological grounding contrasting with Walzer’s primarily secular approach. Johnson’s overview (Johnson 1981) is undermined by his attempt to be historian, philosopher, and theologian, but it remains an important resource. Coates 1997 offers an accessible overview, which is not too partisan between the alternatives that are carefully set out. The edited collection Frowe and Lazar 2017 provides the most up-to-date review of field, with chapters on many of the themes below, while Frowe 2015 remains the best introduction for the uninitiated.

  • Coady, C. A. J. Morality and Political Violence. Cambridge, UK: Cambridge University Press, 2008.

    Independently develops some similar arguments to McMahan and Rodin but in a style more redolent of Walzer (and therefore more accessible to undergraduates).

  • Coates, A. J. The Ethics of War. Manchester, UK: Manchester University Press, 1997.

    Accessible introduction to just war theory, setting it in the context of realism, militarism, and pacifism.

  • Frowe, Helen. The Ethics of War and Peace: An Introduction. 2d ed. Abingdon: Routledge, 2015.

    By far the best entry point to contemporary debates. Clear and covers a wide variety of topics. Designed to complement an undergraduate course.

  • Frowe, Helen, and Seth Lazar, eds. The Oxford Handbook of Ethics and War. Oxford: Oxford University Press, 2017.

    Gives a definitive and up-to-date overview of both historical just war theory and contemporary debates. Leading cast of contributors. The chapters aim to be introductory while also presenting a positive view. Useful for both beginners and specialists.

  • Holmes, Robert. On War and Morality. Princeton, NJ: Princeton University Press, 1989.

    DOI: 10.1515/9781400860142

    A pacifist critique of just war theory that makes up in vehemence for what it lacks in subtlety.

  • Johnson, James Turner. Just War Tradition and the Restraint of War: A Moral and Historical Inquiry. Princeton, NJ: Princeton University Press, 1981.

    Johnson’s approach tends toward a scholastic deference to the authority of a just war tradition that he undoubtedly shapes in his own image, but he remains a key figure in the debate.

  • McMahan, Jeff. Killing in War. Oxford: Oxford University Press, 2009.

    DOI: 10.1093/acprof:oso/9780199548668.001.0001

    The leading contemporary critic of, and alternative to, Walzer. This book summarizes and updates fifteen years of articles against Walzer. It is far more rigorous, but correspondingly less fluent.

  • Ramsey, Paul. The Just War: Force and Political Responsibility. 3d ed. Lanham, MD: Rowman & Littlefield, 2002.

    A Protestant approach to the ethics of war, deeply influenced by the Cold War and the nuclear standoff. Broadly accessible. First published 1968 (New York: Scribner).

  • Rodin, David. War and Self-Defense. Oxford: Clarendon, 2002.

    DOI: 10.1093/0199257744.001.0001

    Philosophically rigorous demolition of conventional assumptions about the justification of national defense, this text also introduces important innovations in the critique of Walzerian principles of jus in bello.

  • Walzer, Michael. Just and Unjust Wars: A Moral Argument with Historical Illustrations. 4th ed. New York: Basic Books, 2006.

    Undoubtedly the wellspring of contemporary just war theory; as accessible and interesting to military practitioners and historians as it is to philosophers—though its fluency comes at the cost of philosophical rigor. First published 1977.

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