If we choose to believe in a morally diminished America, an America that pursues its narrow selfish interests and no more, we can take that course and see how far it gets us. But if we choose to believe that America is not just a set of borders, but a set of principles, we need to act accordingly. That is the only way we ensure that our founding document, and the principles embedded within, are alive enough, and honorable enough, to be worth fighting for.