In a lengthy essay for First Things, George Weigel seeks to begin the fashioning of a foreign policy that moves forward from the United States’ tendency to swing back and forth between two guiding approaches. During some periods of our history, a progressive Protestant idealism has prevailed:

It set a high value on motive or intention and was not much concerned with an analysis of possible consequences (the purity of the actor’s will being what most counted)–and thus it was chary of the idea of a “national interest.”

That national interest has been championed, and has ruled the day during other periods, by realists who conclude, essentially, “that foreign policy is the realm of amorality.” Such a view is not an endorsement of immorality, but an admission that international relations are from interpersonal relations and the determination that the needs of the nation trump.
In some ways, the ten principles that Weigel describes as components of his solution represent a honing of Catholic neoconservatism. The basic assumptions are that states must behave morally — and that war can be a moral action — but that the rules that govern the behavior of nations operate somewhat differently than those by which individuals live their lives. Thus, his number 7 encourages engagement beyond what realists might accept:

It is in the American national interest to defend and enlarge the sphere of order in international public life, through prudent efforts at changing what can be changed in the trajectory and conduct of world politics.

But that is restrained by Weigel’s number 8:

National purpose is not national messianism. The national purpose is a horizon of aspiration toward which our policy (and our polity) should strive. That horizon of purpose helps us measure the gap between things as they are and things as they ought to be, even as it provides an orientation for the long haul. But “national purpose” as defined above is not something that can be achieved in any final sense, because international public life will never be fully domesticated, save under a particularly stringent global tyranny. Understanding national purpose as an orienting horizon of aspiration is a barrier against the cynicism that is the shadow side of realism–and, at the same time, a barrier against the dangers of a moralistic, even messianic, notion of national mission, which implies a far shorter time line and the possibility of final accomplishment.

In short, the objective is a foreign policy that acknowledges a national vision for an ideal world and labors toward that end, but that is realistic about what can be accomplished and cognizant that admirable ends do not justify any means that appear efficient in the short term.