Security has long been a central organizing concept of international relations. Until the 1980s, students of the discipline understood its simple essence in terms of arms races and balances of power. However, the issues have changed considerably in the 1990s, and this text aims to help students understand these changes. Many attempts have been made to redefine the concept, leading to a proliferation of terms such as true security, global security, common security and environmental security, but there has been little precision associated with the use of these terms which have often been used...