The book is an introduction to new debates in international relations. It shows why anyone who wants the best answer to foreign policy problems, like how to deal with North Korea's nuclear arms program, must look at debates in IR theory, and also debates in metatheory. The latter involve questions about whether IR is much or little like the natural sciences, whether prediction is possible, and the like. The book poses policy questions intended to motivate students to think critically about the assumptions and beliefs that underlay particular policy recommendations. It shows the specific links between those policy choices and principles of international relations theories and the further links to philosophical claims about how to choose the best theory. The book thus shows why it is important to examine and contrast the competing scientific-style rationalist foundations of social science theory with constructivist and postmodern positions, since each offers a different way of understanding what constitutes a good theory of international relations.