Last year’s Western decision to intervene in Libya prompted some debate, but the scale of the conflict and its fairly swift conclusion limited the debate to some extent. But the growing tally of atrocities and the thousands of casualties in Syria have necessarily amplified the arguments being conducted as both the United States and its European allies continue to stand aside from the fighting there. As the weeks go by and new outrages are reported, it is increasingly clear to even the optimists in the Obama administration that the Assad regime will not go unless they contribute materially–giving him the push. Consequently, the debate among informed observers about the wisdom of intervention is growing in intensity.

Among the loudest of voices opposing intervention is scholar Daniel Pipes, who writes in National Review to urge the West to stay out of the Syrian morass. While acknowledging the arguments that allowing civil strife there to continue might be dangerous, he argues that such a war might actually be in America’s interest so long as the U.S. doesn’t get dragged in. Walter Russell Mead is more equivocal about intervention than Pipes. But Mead writes in his blog at The American Interest that the humanitarian argument to be made on behalf of intervention is weaker than we think. Both make strong arguments, especially Mead, who acknowledges that there are no good answers here. He’s right about that, but the alternative of a long war there or an Assad victory is not an acceptable outcome.

Pipes is right to worry about the nature of a successor regime to that of Assad. Given what other so-called Arab Spring protests have led to elsewhere, his prediction of an Islamist government following the dictator is probably on target. And Mead does an excellent job of pointing out that the blowback from even an intervention that seemed as clean as that in Libya can be far greater than we think. The current troubles in Mali are a direct result of what happened in Libya, so the moral calculus there wasn’t as neat as some of us thought.

Mead is also correct that even the most successful of Western interventions will not give us a storybook ending. But as even he points out, the situation in Syria isn’t a purely humanitarian question. As much as he deplores the “Wilsonian” instincts of those of us who believe it is morally insupportable for the West to stand by and let thousands die when we can do something to stop it, he also understands that:

If we don’t act, others will. The arming of the Sunni opposition by Gulf Arabs, some with Salafi sympathies, will go on no matter what we think or say, and that is likely both to affect the balance of power within the Syrian opposition in ways we don’t like and to change what happens on the ground. At the same time, our strategic interest in pressuring Iran and in that way hoping to avoid a war between the U.S. and Iran makes the ouster of the Syrian regime a much more important goal than it might otherwise be.

Pipes’ arguments in favor of allowing a Syrian civil war to fester also are not convincing. Such a war might distract the bad guys there from committing enormities elsewhere as he suggests, but I also think he is way too optimistic about Iranians taking a lesson from Syria and starting a revolt against the ayatollahs. Nor do I believe that the blowback from Assad’s reign of terror will channel much Middle Eastern outrage against Moscow and Beijing even though it would be well-deserved.

The main argument in favor of action isn’t purely humanitarian, and it rests not so much on what we think will happen as a result of our intervention. Rather, it rests on what will happen if we don’t. Assad’s survival will mean not just more Syrian slaughter but will be a huge victory for his Iranian allies that will strengthen their position enormously. One way or another, the West needs to prevent that from happening. The reasons for not doing something about Syria are like those for not doing something about the Iranian nuclear threat. The consequences of intervention will be messy and possibly awful. Yet the alternative is far worse.