There are two general approaches to understanding the causes of international conflict. Realism implies a pessimistic view of the usefulness of international institutions in preventing conflicts. Strong international institutions can only exist when there is sufficient agreement among the great powers to allow them to exist. Disharmony among great powers makes strong international institutions impossible. Liberalism supports trade, since trade makes nations more interdependent, and so less likely to go to war.
Liberals also note the democratic nations almost never war against one another.
Nye argues that neither view is adequate on its own. By drawing upon elements of both perspectives, Nye describes two sources of great power conflict. First, power transitions often lead to conflict. Declining nations may attempt to put down rising competitors. Sensing weakness, growing nations may attack declining ones to secure a more favorable place in the international system.