Arguments have consequences in world politics that are as real as the military forces of states or the balance of power among them. Neta Crawford proposes a theory of argument in world politics which focuses on the role of ethical arguments in fostering changes in long-standing practices. She examines five hundred years of history, analyzing the role of ethical arguments in colonialism, the abolition of slavery and forced labour, and decolonization. Pointing out that decolonization is the biggest change in world politics in the last five hundred years, the author examines ethical arguments from the sixteenth century justifying Spanish conquest of the Americas, and from the twentieth century over the fate of Southern Africa. The book also offers a prescriptive analysis of how ethical arguments could be deployed to deal with the problem of humanitarian intervention. Co-winner of the APSA Jervis-Schroeder Prize for the best book on international history and politics.