In this very useful book, the political scientists John J. Mearsheimer and Sebastian Rosato warn against a logic that leads to war: America is challenged by an evil dictator who will not respond rationally to incentives. Such a person can be dealt with only through overwhelming force and must be eliminated from the scene. Today Vladimir Putin and Kim Jong Un are the world’s irrational dictators, and in past years it was Saddam Hussein.

The fallacy in this way of thinking, Mearsheimer and Rosato aver, is that these dictators, however evil we may consider them, and the states they represent are in fact acting in a rational way. This at once raises the question of what counts as rational, and the authors answer that a policy is rational if it aims at the preservation of the state, is based on a credible theory, and is arrived at through a deliberative process that doesn’t exclude alternatives.