Now consider another signal intervention would allegedly send.

Imagine that we fire cruise missiles into Syria. Would that really send a signal to North Korea that we would not tolerate their use of chemical weapons? Whatever one thinks about an American attack on Syria, it is unlikely to lead to a nuclear war on the Korean peninsula, or the deaths of thousands of American troops stationed in South Korea, or a potentially catastrophic confrontation with China -- all of which could happen if we attacked North Korea after it used chemical weapons on its own people. And the North Koreans surely understand that the strategic calculus behind attacking Syria for chemical-weapons use would be different from the factors Obama would weigh if it were North Korea. Signal Hawks often act as if foreigners will be totally oblivious to the obvious.

Despite all the talk about red lines and the "necessity" of responding to the use of chemical weapons with force, everyone in the United States and the world understands that the United States would not go to war with Russia, or China, or North Korea, or Pakistan, if one of those countries used chemical weapons on their own people. No foreign government is so simpleminded as to think, "The Americans responded to chemical weapons in Syria by striking the country, so they're obviously going to respond in exactly the same way to any other country."

Whether or not we attack Syria, "rogue regimes" will know, as well as we do ourselves, that "getting away with" future use of chemical weapons depends not on precedent, but on the offending country, its international alliances, its military strength, the U.S. president at the time and his or her priorities, and three dozen other factors. The Signal Hawks' faith in absolute transitivity is as strong as it is baffling.

Arguments that turn on signal-sending so often adopt assumptions about the signal to be sent that are highly questionable at best, and that are, at worst, simplistic, naive, and totally lacking in rigor. Their advocates never seem to look back and notice the signals that don't work. The Iraq invasion was predicated in part on the fact that Saddam Hussein gassed his own people, and the belief that he had chemical weapons. Yet neither the Iraq invasion nor the execution of Saddam Hussein stopped chemical weapons from being used in Syria.

And what are we to make of the argument that we must intervene because "the world is watching"? It might make sense as a hawkish talking point if most of the world decidedly favored intervention, but that is far from true. The parliament of our closest ally, along with the British people, thinks intervention is a bad idea. Neither the UN nor NATO will endorse intervention, and it's hard to imagine that, say, Brazil or Canada or India will change its attitudes toward America in any salutary way if and only if we send cruise missiles or bombs into Syria.