Beyond a reasonable doubt, the forces of Syria's Bashar al-Assad used chemical weapons on a large scale and should be punished. That's where I end up. But the case isn't cut and dried.
Sometimes, standing on principle doesn't get you very far. The problem is, which principle? The norm forbidding use of chemical weapons, the norm of restraint in use of military force and the norm of upholding international law are in conflict. In addition, predicting the results of action (or inaction) is a matter of weighing probabilities, not certainties.
If you're sure you know what's right in this case, you haven't thought it through. I don't criticize U.S. President Barack Obama for being oppressed by these complexities, as he seems to be: Better that than a leader who thinks it's all so simple. I wish he would make decisions faster and pitch a more confident case for the course he has chosen -- you can be careful without dithering -- but he's not wrong to see this as a difficult choice.
Options have narrowed. Maybe there was a case for intervening to overthrow Assad at the outset, but his domestic enemies are no longer clearly preferable, and the U.S. lacks the will and the means to reshape a postwar Syria. The choice is between a limited punishment strike or softer censure such as jawboning, sanctions and indictment of Assad under international law.
Choosing not to use force would weaken the norm against chemical weapons. Those milder ways of expressing disgust would still be available, so the norm wouldn't be destroyed -- but it would be eroded. Preventing that is both morally right and valuable to the U.S. and the world. But how valuable? And at what cost?
The wider the support for any action, the more effective it would be in upholding the norm. In this case, time isn't critical, so Obama (doubtful as one may be about his motives) is right to look for the broadest possible backing at home and abroad.
It's a shame that Russia and China won't go along -- but their calculations are so transparently cynical that their refusal has no moral force. Their reflexive noncooperation merely weakens the conflicting international-law norm. In this case, their objections should be disdained and dismissed.
Yet you can't dismiss the lack of support among U.S. allies or among U.S. citizens. If the U.K. isn't willing to join airstrikes against Assad, that in itself undermines the chemical-weapons taboo. The same would be true for punitive attacks that weren't supported in the U.S. Congress or across the country. Remember, the aim isn't just to damage Assad militarily, which the U.S. could do without allies or congressional approval, but to express a moral consensus. If that consensus turns out not to exist -- or if it exists in theory but is spineless in practice -- the case for action falters. We'll have discovered that the taboo against chemical weapons was so much posturing.
Obama says he's made his decision and has the right to act regardless of what Congress decides. Striking Syria even if Congress says no would be a remarkable gamble. It would also be less potent (because the norm would have been eroded in any event) and on balance unwise. Does that mean he was wrong to ask for authorization? Again, no. The more backing Obama can muster, the stronger the affirmation -- and that's what counts.
What about U.S. credibility? Most of those urging an attack say it's on the line. They have a point -- credibility matters, to be sure -- but they're making too much of it. Obama was wrong to say that chemical weapons were a "red line" in Syria without being sure he meant it. Making threats you aren't ready to carry out is dumb. He did say it, and failing to follow through would therefore cost something. But much of the damage is done. Obama draws red lines first, then thinks about whether to enforce them. This knowledge can't be unlearned.
Would failing to attack Syria make Obama's promise to stop Iran getting nukes less credible? I doubt it. An Iran with nuclear weapons is vastly more threatening to U.S. interests than a Syria willing to use chemical weapons on its own people, and deterring it is a far more challenging prospect. The cases are too different. The credibility argument counts for something, as I say, but it's exaggerated.
No, the core of the case for action, so long as Obama can win sufficient support, lies in upholding the moral prohibition. And the valid case against turns not on legality or credibility but on the risk of unintended consequences.
All being well, airstrikes could achieve their goal at little cost, deflect Assad from using chemical weapons again and make other morally bankrupt regimes think twice. But they would also cause collateral damage and kill innocent civilians. It's conceivable that Assad would reap a propaganda advantage. He could start using chemical weapons even more aggressively, daring the U.S. to respond again -- knowing that escalation might carry Obama into an outright war the U.S. doesn't want to fight.
There could be terrorist retaliation against the U.S. Whether the U.S. intends it or not, airstrikes might swing the civil war against Assad and lead his regime to collapse -- with results that would be good or bad for most Syrians, and for the U.S. and its allies, depending on who takes over.
I defy you to consider those possibilities and say the case for action is open and shut. Assad's use of chemical weapons doesn't present a clear and present danger to the U.S.; let's not pretend otherwise. Everything comes down to the importance of the chemical-weapons taboo.
Are these weapons really so vile, as governments have been saying for more than a century, that their use should be met, where feasible, with force? Or will they be something we learn to accept, just one more horror of war, along with all the others we deplore yet find ways to tolerate? It's a close call. I think the taboo is worth defending, and the prize worth the risk. I hope Congress agrees.
Clive Crook is a Bloomberg View columnist.