In the century of two world wars and a Cold War one could have been forgiven for thinking that everything important was determined by the movement of world affairs. Now the reverse seems true. International relations are commonly discussed as if hostage to US election campaigns, to the emergence of some new populist movement in Europe, or to the health of the Chinese economy. In universities, although the subject of International Relations is in great demand, its definition in relation to other social sciences, notably politics but also sociology, economics, geography and law, can seem ever more blurred. This lecture considers what, if anything, is still distinctive about the international realm, and what that implies for its future academic study.