The state system is a distinctive way of organizing political life on earth which las deep historical roots. There have been state systems at different times and places in different parts of the world: for example, in ancient India, in ancient Greece and in Renaissance italy (Watson 1992). However, the subject of IR conventionally dates back to the early modem era (sixteenth and seventeenth centuries) in Europe, when sovereign states based on adjacent territories were initially established. Ever since the eighteenth century the relations between such independent states have been labelled international relations. In the nineteenth and twentieth centuries the state system was expanded to encompass the entire territory of the earth. The world of states is basically a territorial world: it is a way of politically organizing the world's populated territory a distinctive kind of territorial politi- cal organization, based on numerous different governments that are legally independent of each other. The only large territory that is not a state is Antarctica, and it is administered by a consortium of states. Today IR the study of the global state system from various scholarly perspectives, the most important of which shall be discussed in this book.