"You express your contempt for populism, and I might agree. However, if a State's interest should not be based on the popular interests of the people contained therein, then upon what should it be based?"
We accept as a truism that corporations acting for their own profit enhances the well-being for those who work for the corporation. If a corporation makes gains those gains could translate into more jobs, pay raises, etc. States, in an international environment of de-centralized authority and security competition, have even more reason to maximize their "profits", in the form of power and influence. People, generally speaking, do not understand the long-term strategic implications of foreign policy decision-making. The Germans probably ignore the fact that their generous welfare state came not as a result of liberal do-gooders or even working class radicals, but as a result of Otto von Bismarck's Blood and Iron foreign policy. War, more than anything else, is responsible for the expansion of social spending and the welfare state. Why? Because state leaders wanted a healthier population with which to use to fight wars.
Would the average German populist have understood that it took careful strategizing and three wars to create the conditions necessary to unify Germany? I don't think it's likely. They're adverse to sacrifice, think in the short-term, and only want to do what is popular, avoiding tough decisions. Bismarck, by calculating what would maximize Prussia's power, unified Germany and brought unprecedented prosperity to the German people.
So to answer your question, States should behave in such a way as to maximize the overall power and influence of their state. Operating according to any other principle will sacrifice the long-term security of the state for short-term popularity, or the long-term security of the state for utopian fantasies of a law and morality based international order.
Would you argue that the average person only thinks they know what they want, but an educated person actually has more insight into what the average person *really* wants? Or perhaps you would only argue an educated person knows better how to achieve these wants?"