What is the relation between politics and the world? It might seem that global capitalism has created one world, but this is an illusion because capitalism creates a world of objects and money that divides human existence into regions separated by fences and walls built to keep some people out. In place of this falsely unified world of global capitalism, we need to assert a fundamental principle - namely, that there is one world of living subjects. This, in Badiou's view, is the categorical imperative of all true politics. The one world of living subjects is the place where an infinity of differences and identities exist.  Hence foreigners are not a problem but rather an opportunity and a gift. They bear witness to the youth of the world in its infinite variety, and it is with this youth that the politics of the future rests. Foreignness is the means by which existence is re-evaluated, and all true politics is a new dawn of existence. This collection of essays by Badiou, in which he draws out the political implications of recent events and social movements, will be of value to anyone interested in the great social and political questions of our time.