This chapter explores some of the recent literature on empirical and normative implications of intervention and non-intervention in the international arena. These concepts are not, of course, unique to international politics. They characterise a wide variety of activities in different social and political arenas. But the role of these concepts in international politics is distinctive because the principle of non-intervention is firmly and now formally embedded in the normative conventions governing international relations. In contemporary international law states are clearly proscribed from intervening in the domestic affairs of other states. Intervention is, under most circumstances, an illegal act. By contrast, the state has extensive rights of intervention within its own boundaries. Indeed, the history of the modern state can be charted in terms of its growing powers of intervention in the lives of its citizens.¹