Liberals, by and large, took away an altogether different lesson from Vietnam. For them, there was always something tragically flawed about the way policymakers insisted on seeing the conflict through a prism of good vs. evil, when the reality on the ground was so much more nuanced. This simplistic notion of falling dominoes was to them a kind of madness, locking leaders into the same trajectory year after year, long after it was clear they were headed nowhere useful.

And so basically every Democratic president (and nominee) in the past 40 years has resisted any sort of unified string theory for world affairs. Bill Clinton cast around for a slogan early in his tenure (Madeleine Albright, his United Nations ambassador and then secretary of state, tried out “assertive multilateralism,” which I guess might be like muscular multilateralism, only more robust), but ultimately Clinton settled for confronting post-Cold War chaos on a pragmatic, ad hoc basis.

As the party’s first nominee after the terrorist attacks of 2001, and its first to have seen combat in Vietnam, John Kerry was especially averse to binary doctrines. He cast doubt on Bush’s construct of a war on terror, but he steadfastly refused to offer any tidy, alternative way of looking at the threat, which had the effect of making him a less comprehensible candidate at a moment when voters were looking for exactly that.

Obama is, if anything, even more circumspect. Hillary Clinton was only partly right when she said that “Don’t do stupid stuff” wasn’t a framework for foreign policy; in fact, the phrase mocks the very concept of a framework.