World peace is receding. In 2025 there were more state-based armed conflicts than in any year since 1946, and global freedom declined for the 20th consecutive year. The 2026 Global Peace Index recorded a 12th consecutive annual decline in global peacefulness.
Maintaining international peace is the first purpose of the United Nations, yet international law has no agreed definition of peace. One recent review of the research counted 61 different concepts of it. Doctors judge a treatment against an idea of what health looks like. Without an equivalent idea of peace, we cannot tell whether our laws are designed to produce it.
In a new article in the Journal on the Use of Force and International Law, I propose one, which I call the Sovereignty of Sentience. It is a philosophical argument built only on what each of us can know for certain from our own experience, and it leads to a single test for peace that, I argue, works at any scale, from a household to the United Nations.
You can only be certain of your own experience
You know you are a sentient living being with experience that matters to you: there is something it is like to be you. You see, feel, worry and hope. But that experience is private. You cannot step inside anyone else’s, and no one can step inside yours. Your neighbour is almost certainly sentient too, yet you can never prove it – an MRI scan of her brain would not show you what a sunset looks like to her – nor can you prove your own sentience to anyone else.
In this sense, each of us is sovereign over our own experience, which is where the Sovereignty of Sentience takes its name. Sovereignty here means authority over your own life, as opposed to the sovereignty of states.
To protect yourself, you have to protect every being that might be sentient
Suppose we agreed to protect only those who could prove they were sentient? No one could pass that test, including me.
Suppose instead that protection went to whoever was strongest? That works only while you stay strongest, and no one does for ever.
Each of us survived infancy because others cared for us when we were powerless and could prove nothing, and illness, injury or old age can leave any of us powerless again.
So the rule that best protects you, even if you care only about yourself, is to treat every being that might be sentient as if it is: with respect. I call this the presumption of sentience. Like the presumption of innocence, it decides how we treat someone without claiming to know the truth. Erring on the side of care costs little. Erring the other way creates a rule under which any of us could be treated as a thing.
Peace means four protections holding for everyone
Only you can know what your wellbeing needs, so peace cannot protect wellbeing itself. What it can protect is your freedom to pursue it on your own terms. That needs four things from everyone else:
- Subjecthood: being treated as a someone, not a something.
- Jurisdiction: being treated as the only authority on your own experience, without others deciding for you what you feel or need.
- Liberty: having real choices and the means to act on them.
- Security: safety for your body, your boundaries and the life you have built.
Peace is the condition in which all four hold for everyone. Violence is any one of them failing for anyone. Justice is the everyday work of preventing those failures and repairing them.
Disagreement is a normal part of a healthy peace, and a peaceful society gives it somewhere to go, such as political debate in democracy, where it can be worked through without anyone’s protections being broken.
International law both bans force and permits it
Measured against this test, international law is split in two. One part upholds the four protections, including the ban on the use of force, the rules shielding civilians in war, and human rights law. The other part permits violence, such as self-defence and military action authorised by the Security Council. The UN’s own structure also falls short of the test, because five permanent members hold a veto and any change to that arrangement needs their agreement.
I accept that self-defence can be lawful, necessary, even the “least bad” option available. It still cannot be called peace. A law that limits when force is allowed may make violence rarer, but it also keeps violence legitimate.
To serve its stated purpose, international law would need to prohibit force against any being that might be sentient, and make prevention and repair its default. Force would be kept for objects. In a forest fire, turning the hoses on the flames is force against an object, while helping people to safety is justice. In war, the same logic allows disabling a tank, while the soldiers inside are still owed help to safety.
The article sets this out as a framework to be tested and challenged. If it holds, the same test could guide law well beyond war, from how we raise children to taxes, food and trade.
Reagan, A. (2026). The Sovereignty of Sentience: A Phenomenological Approach to Peace for International Law. Journal on the Use of Force and International Law. doi.org/10.1080/20531702.2026.2742056