A balanced reading path
Where to start with Just war theory
War, realism, peace, and global institutions.
Part of War and international order. This path zooms in on just war theory specifically.
What is just war theory?
Just war theory asks when military force is morally permissible and, having determined it is, how it must be conducted. The tradition runs from Augustine and Aquinas through Grotius and Vattel to Michael Walzer's contemporary framework: the conditions under which a war can be justly begun and the rules that must govern its conduct. It insists that war is not simply beyond morality and that combatants are bound by basic standards whether or not their cause is just.
This path opens with Walzer's Just and Unjust Wars, the definitive contemporary treatment: when is intervention permissible, what is the moral status of combatants, and how should non-combatant immunity be understood? Aquinas's Summa Theologica supplies the natural-law framework in which just war theory was classically developed. Morgenthau's Politics Among Nations provides the realist counterpoint: states pursue interests, not justice, and moral restraints that ignore power will fail. Kant's Perpetual Peace presses from the opposite direction, asking whether the institution of war can be superseded by law altogether.
The 5-book path
- 1Start Here— the accessible entry point
Just and Unjust Wars
Michael Walzer · Just war theory / political philosophy
The authoritative modern account of just war theory. Walzer argues that there is a genuine moral logic to the conduct of war — that wars can be just or unjust, that soldiers and statesmen are morally responsible for how they fight, and that civilian immunity is a real constraint that cannot be overridden simply by military necessity. Essential for any route on war, international relations, justice, or the ethics of violence.
To avoid a bubble: Pair with E. H. Carr or Morgenthau for the realist rejection of moral reasoning in international politics, and with Kant's Perpetual Peace for the cosmopolitan alternative to Walzer's state-based framework.
- 2Classic Foundation— the durable classic that anchors the debate
Summa Theologica
Thomas Aquinas · Natural law / Christian political thought
The towering synthesis of Christian theology and Aristotelian philosophy, and the foundation of the natural-law tradition that still shapes debates over justice, rights, and human law. In its treatise on law, Aquinas argues that human laws derive their authority from a higher moral order — eternal and natural law accessible to reason — so that an unjust law is, in a deep sense, no law at all. Indispensable for understanding natural-law conservatism and the Catholic political tradition.
To avoid a bubble: Pair with legal positivists (Hobbes, and later Austin and Hart) who insist law is the command of the sovereign and need not be moral to be law, and with secular and pluralist thinkers who reject grounding politics in a single divine order.
- 3Modern Bridge— connects the older argument to the present
Politics Among Nations
Hans Morgenthau · Classical realism / international relations
The foundational text of 20th-century IR realism. Morgenthau's argument that international politics is driven by interest defined as power — not by moral principles or international law — defined the discipline of international relations for decades and remains the primary reference point for both realist practitioners and liberal and constructivist critics.
To avoid a bubble: Pair with Kant's Perpetual Peace for the liberal-idealist counter-claim, and with E. H. Carr's The Twenty Years' Crisis for a more historically situated version of realism. Alexander Wendt's Social Theory of International Politics offers the constructivist response.
- 4Opposing View— the serious counter-argument, to avoid a bubble
Perpetual Peace
Immanuel Kant · Liberal internationalism
A foundational liberal text on peace, republican government, cosmopolitan right, and international order.
To avoid a bubble: Pair with realist critiques of international politics.
- 5Contemporary Lens— a current-day perspective
The Tragedy of Great Power Politics
John J. Mearsheimer · Offensive realism / international relations
The most forceful contemporary statement of realism, and a sobering guide to great-power competition. Mearsheimer argues that because states can never be certain of others' intentions in an anarchic world, the safest course is to maximize power — so great powers inevitably compete for dominance, and conflict is a recurring tragedy rather than an avoidable accident. His framework underlies much current debate over the United States, China, and Russia.
To avoid a bubble: Pair with liberals who stress how trade, democracy, and institutions can dampen conflict (Keohane, the democratic-peace theorists), and with critics who argue Mearsheimer's pessimism underrates ideology, domestic politics, and the real record of cooperation.
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Build your own version →Frequently asked questions
- Where should I start reading about just war theory?
- Start with Just and Unjust Wars by Michael Walzer: the accessible entry point. From there this path works through the core texts of just war theory and includes a serious opposing view, so you meet the strongest case for and against it.
- What is a key book for understanding just war theory?
- Summa Theologica by Thomas Aquinas is the durable classic that anchors the just war theory debate. The other books on this path argue with it and build on it.
- What is the strongest counterpoint on this path?
- This path deliberately includes Perpetual Peace by Immanuel Kant as the serious counter-perspective, so you meet the strongest challenge to this path's central ideas rather than reading in a bubble.
- Is this just war theory reading list free?
- Yes. Every PoliReads reading path and book page is free, and no account is required.