A moral theory of justice ought to be practical. This essay sets out the criteria that a theory needs to satisfy in order to count as practical and it argues that at the present time there is no practical theory of global justice that is also morally adequate. This conclusion is reached through a critical examination of the main strategies adopted by philosophers and political theorists for reasoning about justice in global affairs. The failure is not the fault of the theorists. Theories of justice presuppose a state of affairs that does not presently exist in global society. This essay charts the limits of a particular kind of moral reasoning--but does not close off all possibilities for moral reasoning about global issues.