When Morgenthau (in Politics Among Nations) places national interest at the heart of states' decision making, he is making a claim that is both positive (or descriptive) and normative (or prescriptive). On the one hand, he is describing the world as it is. States will make choices that are consistent with their national interest -- and this largely means increasing their power. On the other hand, he is encouraging leaders and policymakers to only act in ways that promote the national interest.

For some critics of realism, this translates, at least potentially, into policies that seek power, without considering their ethical implications. For example, should the U.S. intervene to protect vulnerable or persecuted minorities in other countries, even if there's no direct strategic interest in doing so? When, in your opinion, should ethical or moral considerations override questions of national interest, and compel the U.S. (or any country) to act?