But time and again, Obama has refused the offer. During the 2008 campaign, he called himself the "anti-doctrinaire" candidate -- and he has stuck to that line. The president has been attacked from the right for lacking decisiveness and vision. But if the whole idea of presidential doctrines were relegated to the history books, it would be a fine day for the Republic.

Presidential doctrines are too, well, doctrinal. These proclamations can become a straightjacket that constrains a president's options. Simplistic pronouncements are especially dangerous when we live in a complex world with diffuse threats, as we do today. The Arab Spring, for example, with its distinct local dynamics, requires flexibility -- and even inconsistency. Intervention in Libya does not also mean intervention in Syria.

And there's something very odd about each president getting one and only one doctrine. The Truman Doctrine, after all, came in 1947, just two years into Truman's administration. What if he later had a eureka moment and came up with a second doctrine? Could he scrub out the first, and etch in a replacement?

More importantly, presidential doctrines have a poor record. The Truman Doctrine encouraged a universal definition of U.S. national interests during the Cold War that helped draw the United States into Vietnam. Meanwhile, the Bush Doctrine linked diverse local struggles in an overarching war on terror, lumped Iran and North Korea together in an unlikely "Axis of Evil," and produced a failed policy in Iraq.

This record may explain why other nations haven't copied the idea. Bismarck didn't have a doctrine. Neither did Churchill. These statesmen wanted flexibility in their foreign policy. Churchill once told the British Parliament: "If Hitler invaded hell I would make at least a favorable reference to the devil in the House of Commons."

Is the answer to lurch to the other extreme, and embrace a foreign policy of pragmatism? With new crises keeping the phones ringing at the White House, it's tempting to abandon systematic thinking and focus on the day-to-day. The great theorist Marx once said -- and here, of course, I'm talking about Groucho Marx: "These are my principles and if you don't like them ... I have others."

But the United States cannot simply be reactive or ad hoc in its foreign policy. It must pursue coherent goals. And presidents need to recognize that foreign policy issues are connected, with actions in, say, Afghanistan rippling out and affecting other areas of the world, like a stone thrown in a pool.

We don't need a doctrine, or pure pragmatism. What we require is a middle path: a strategy.

A strategy identifies our core interests and the major threats, and guides presidents in safeguarding those interests. But it avoids cookie-cutter rules, and understands local variation.