Hedley Bull (1932 - 1985) was Professor of International Relations at the Australian National University, and then at the University of Oxford until his death in 1985.

The Anarchical Society (1977) is his main work, and a central text in the so-called ‘English school’ of International Relations. In this book he argues that despite the anarchical character of the international arena, it is characterised by the formation of not only a system of states, but a society of states. His requirements for an entity to be called a state are that it must claim sovereignty over (i) a group of people (ii) a defined territory, and that it must have a government. States form a system when they have a sufficient degree of interaction, and impact on each other's decisions, so as they "behave - at least in some measure - as parts of a whole." A system of states can exist without it also being a society of states. A society of states comes into existence "when a group of states, conscious of certain common interests and common values, form a society in the sense that they conceive themselves to be bound by a common set of rules in their relations with one another, and share in the working of common institutions."

This is only a small part of Bull's argument. He also gives the concept of order, and the mechanisms of: the balance of power, international law, diplomacy, war, and the great powers central roles. He concludes that, despite the existence of possible alternative forms of organization, the states system is our best chance of achieving order in world politics.