the two strands of America's historic foreign policy

An interesting assessment from James Bratt in Books & Culture in a review of George Herring's From Colony to Superpower...

Americans have always struck outside observers as being a bundle of contradictions....

So too, George Herring's massive survey of American diplomatic history runs along a double track...over its 230-year history, American foreign policy has evinced a distinctive consistency that argues the operation of a determinative DNA. One strand is composed of a persistent idealism that wishes the United States to be a blessing to others—at the same time tending to regard these others as either dangerous sophisticates (Europe) or benighted primitives (most everybody else). Refreshingly free of hypocrisy, then, appears to be the other strand, the raw pragmatism that drives Americans to pursue their national self-interest much like any other country.

The problem—or the intrigue—is that the two strands make a genuine double helix, inseparably intertwined. Pragmatism by definition involves adjustment to reality, but the "reality" of a given situation is framed by the idealism with which it was sighted in the first place. Then too, "idealism" itself is composed of mixed quantities: one part good will, one part willed blindness and thus pretense, one part calculated public-relations appeal, thus cynicism—a cynicism that can then invoke the rationale of pragmatic adjustment to cloak both the pragmatism and cynicism with the moral warrant of ideal intentions.