Political thinking anywhere in the world today, as always, is irretrievably contextual. It takes its coordinates from the setting in which it finds itself. Today that setting is ever more, and unmistakably global. Whilst human populations have never been fully insulated from each other in our epoch, all of them have for some time been undergoing a process of at best, semi-voluntary de-insulation which still appears to be accelerating. However clumsily or dishonestly it may do so, contemporary political reflection has no option but to register that de-insulation as best it can and try to judge what it means. In this lecture, John Dunn argues that we now face a pressing need for a global history of political thought, and that our need is increasingly urgent and not mainly academic, and that we must recognise it promptly and frankly and set ourselves vigorously to learn how to satisfy it better.