Anne-Marie Slaughter relies  heavily on the “credibility” argument for Syrian intervention:
U.S. credibility is on the line. For all the temptation to hide behind the decision to invade Iraq based on faulty intelligence about weapons of mass destruction, Obama must realize the tremendous damage he will do to the United States and to his legacy if he fails to act. He should understand the deep and lasting damage done when the gap between words and deeds becomes too great to ignore, when those who wield power are exposed as not saying what they mean or meaning what they say.
Not one of these claims is true in this case. It is foolish to promise U.S. action and fail to fulfill that promise, but in the Syrian case it is not yet clear that such action is needed, nor is it clear what action was actually promised. I don’t know what may happen to Obama’s “legacy,” and frankly it doesn’t interest me. I am sure that it will not do “tremendous damage” to the United States if Obama chooses not to ensnare us in yet another dumb war. I suspect that the U.S. will not suffer much damage to its credibility, either.
Consider the effects on U.S. credibility from the invasion of Iraq. No one can say that the Bush administration didn’t follow through on its threat to go to war. Bush meant what he said when he said that the U.S. would invade Iraq and depose Hussein. U.S. credibility was not maintained by Bush’s decision to follow through on the threat. Instead, the already weak justification for war was exposed as false, and the decision to invade damaged the country’s reputation around the world. If it turned out that sarin was used by accident or its use wasn’t authorized by the regime, and the administration makes the error of heeding the calls for war, everyone now clamoring for a Syrian war will look as ridiculous as all of the Iraq war hawks did when the promised weapons and weapons programs were nowhere to be found. Following through on threatened action can still be a horrible blunder if the action is foolish and reckless. When contemplating starting a war, it is always far better to err on the side of restraint. Considering how limited the supposed use of sarin in Syria has been and how uncertain the evidence for this use is, the eagerness with which so many interventionists from both parties are seizing on this as the excuse for war is horrifying.