President Barack Obama’s final State of the Union address offers foreign-policy commentators one last chance to take a stab at defining what the Obama doctrine is — or should have been. It will also mark a new phase in the 2016 presidential campaign, with ensuing opportunities to speculate about what the Hillary Clinton, Ted Cruz, or Marco Rubio doctrines might look like.

Amid all the analysis, a bigger question will almost certainly escape notice: Why are we desperate for presidential doctrines in the first place? Since Harry S. Truman’s administration, almost all of them have turned out to be either disappointments or disasters.

If Obama ends his second term without a doctrine to his name, we should all be grateful.

As American high school students learn, the United States’ passage from colony to global superpower was attended by one foreign-policy doctrine (James Monroe’s) and one corollary (Theodore Roosevelt’s). That changed after World War II, when the 1947 Truman Doctrine sparked a proliferation of imitators. The Cold War gave U.S. presidents a newfound interest in communicating U.S. polices and red lines to the Soviet Union, while journalists and commentators developed an interest in defining these presidential pronouncements as doctrines. Some proved more specific than others, but none of them ever proved terribly successful. If presidential doctrines eventually came to be seen as a sign of strategic wisdom, it’s only because Washington’s eventual victory over the Soviet Union gave them a gloss they didn’t earn.

In March 1947, Truman told a joint session of Congress that he believed “it must be the policy of the United States to support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures.” Specifically, the president was asking Congress to fund military and economic aid to Greece and Turkey, both subjects of Soviet interest at the end of World War II.

This proved to be the early high-water mark for presidential doctrines. Soviet ambitions in the eastern Mediterranean may not have been as aggressive as U.S. policymakers feared, but Truman’s show of support nonetheless ensured that Greece and Turkey would remain firmly on America’s side for the rest of the Cold War. Indeed, when both countries joined NATO in 1952, Truman’s policy became a lasting part of Washington’s European defense architecture and its broader strategy of containment. ...