The fact that the entire population of the world is divided into separate territorial political communities, or independent states, which affect the way people live, is a good reason to study International Relations. Together those states form an international system that is global in scope. Everybody on earth with very few exceptions, not only lives in one of those countries but is also a citizen of one of them and in some cases, of more than one. So every man, woman, and child on earth is connected to a particular state, and through that state to the state system which affects their lives in important ways that they may not be aware of.