The last few days in my Political Science classes have been focused on power politics and ideas of the national interest. In summary, the Realists such as Morgenthau believe that the only thing which is in any country's national interest is the pursuit of power, which is inherently a zero-sum transaction given that if you have a finite power potential, one country's gain implies another country's loss. The ideal situation in politics is the presence of a balance of power between nations that forestalls war.
This is not necessarily an amoral position. Morgenthau escaped from Nazi Germany, and he believed that the failure of the European nations to contain Hitler was directly related to their unwillingness to put power politics before all other considerations. Furthermore, the international norms of behavior (such as they are in a Realist world) are dictated by the most powerful countries. Ergo, a Realist governed by moral concerns (it sounds contradictory, I know, but it isn't) could argue that the most moral countries have a moral imperative to behave immorally if necessary to extend their power! If they do not do so, they will fall to less moral challengers, with harmful consequenses for the people of the world. Thus, policies driven by explicit concerns of morality only divert strength from the important needs of power politics, ensuring disaster.
On the other side are the idealists, who believe that strong nations have the moral responsibility to promote morals with their power. How can we stand aside in Rwanda, for example, by saying that it is not in our national interest? According to the idealists, it is in the national interest of all nations to promote a more stable and just international system, even if a nation must take a short-term hit in the process.
Complicating things is the fact that the changing world has rendered large parts of the classic Realist position obsolete. With the advent of large-scale terrorism and similar dangers, maintaining the balance of power is not enough to ensure peace. State-sponsored terrorism in particular creates a large bias towards regime-change in the absence of more traditional power-political concerns. Furthermore, power has ceased to be a zero-sum game in many respects, particularly in the areas of trade and knowledge, thus removing many of the classic objections to some policies based on cooperation. As well, we should consider Dr. Matthews' 1989 argument that I mentioned earlier, that many of the pressing challenges we face today can only be dealt with on a regional level, and not by individual states.
America is in the unusual position of being so powerful that she can ensure her own security with vast resources to spare. I believe that this is a key factor. Our first responsibility should be to retain our position as hegemon of the world, for several reasons alluded to above; but we must also use the rest of our strength to advance democracy, capitalism and the welfare of mankind. This is particularly true since we have means at our disposal that increase our power as opposed to decreasing it, such as free trade. But it is even true if we should need to sacrifice some of our power for the good of others, because we have so very much to spare. We should of course be vigilant not to get carried away, as happened after World War I, and keep our main focus on power politics. But I believe that God will eventually reward those who act kindly and justly with others, all else being equal. The national interest is broad enough to include the cause of freedom.