A major new textbook on International Relations theory written by a leading scholar, suitable for any course on IR theory at either undergraduate or master's level. The text goes beyond an exploration of the main contending theories in IR and provides cross-cutting coverage of current key issues and debates. Jørgensen also examines the philosophical commitments behind the different theories and suggests how different philosophical formats shape theories differently and trigger different research agendas. In addition there is a unique chapter explaining how to do theory, which guides students in applying their own theories about world politics to their studies. An essential read for students of Politics and IR.