International relations deals with the relationships between political bodies and the wider world-systems created by their interactions. These entities include sovereign states, inter-governmental organizations, international non-governmental organizations, other multinational corporations. International relations is both an academic and a public policy field and studies politics, economics and law on a global scale. Since it analyzes and formulates the foreign policy of a given state, it can be both positive and normative. International relations and affairs form a separate, highly inter-disciplinary academic program from political science. Some of the schools of thought which are studied within this field are realism, liberalism, constructivism and Marxism. This book examines the origins and evolutions of international relations in detail. It traces the progress of this field and highlights some of its key concepts and applications. This book will serve as a valuable source of reference for graduate and post graduate students.