On why I was ready to hear his case, once he decided to make it to Congress: I had obviously been skeptical of unilateral military involvement Syria. A week ago we were headed toward action that was unilateral in two ways. One was the absence of UN, NATO, EU, UK, or other broad alliances that have been amassed for nearly all modern military strikes. The other was the domestic unilateralism of Obama's deciding this all on his own.

For me, the very fact of going to Congress made the plan presumptively more legitimate. If we went ahead, it would be a national decision, not one man's choice. A broader and more systematic U.S. process might in turn attract wider allied backing -- which in its turn could mark any action as a defense of truly international, not just American, norms. And the need to testify and debate in Congress, even this madhouse Congress, would ensure that basic questions about evidence, plans, and contingencies got asked and (presumably) answered. Therefore I thought a week ago that after hearing a case made, in these legitimizing circumstances, I could imagine being convinced that Congress should offer the support that the president, to his credit, had requested rather than assumed. Overall, we might have a least-worst outcome: bipartisan agreement, American leadership, reinforcement of the anti-chemical norm.

On why I would now vote No: From what I can tell, approximately 100% of the pro-strike arguments have been devoted to proving what no one contests. Namely, that hideous events are underway in Syria, that someone (and most likely Assad) has criminally and horrifically gassed civilians, and that something should be done to reduce the ongoing carnage and punish the war crimes. And approximately 0% of the argument has addressed the main anti-strike concern: whether U.S. military action -- minus broad support, any formal international approval, or any clear definition of goal, strategy, or success -- is an effective response.

For instance, Nicholas Kristof of the New York Times, with whom I usually agree, argues powerfully something should be done to and for Syria. His case for missile strikes is that they "just might, at the margins, make a modest difference." If anyone has seen a defense that says, "These steps, in this way, match means to objective, and have the following path to success," please let me know.

There is such a thing as too much caution in committing force, often known as McClellanism after the reluctant-warrior Union commander at the start of the Civil War. (Leading of course to the famous line attributed to Lincoln, "If General McClellan does not want to use the army, I would like to borrow it for a time.") And nations, like individuals, predictably over-learn the lessons of their most recent mistakes.

But even if the Iraq-war disaster had not happened, even if the tiny handful of Americans who are in the military had not been worn out through a decade-plus of nonstop deployments, any decision about use of force should be accompanied by answers to these most basic questions: