First, we are protecting ourselves and our allies. We cannot afford to live in a world in which nations can use chemical weapons with impunity. The taboo against chemical weapons is particularly strong, for good reason. Dying by the breath we need to live holds a particular terror. The parents of the children whose shrouds we see could not protect them even with their own bodies, like human shields from a bullet or a bomb…

Second, striking Syria now will be a strike to protect the Syrian people, even if partial and belated. It will not end the massacres carried out with conventional weapons. But weapons of mass destruction are just that: weapons of mass destruction. A chemical attack that kills 1,000 today can kill 10,000 tomorrow and 100,000 the day after that.

Third, the president is asking us to do, as a nation, what a leader has to do. In his 2008 inaugural address, Obama called for a new era of responsibility in this country, “a recognition … that we have duties to ourselves, our nation and the world.” We have those duties not because the United States has some unique role or mission in the world, but because we are the world’s most powerful nation. Other nations take their cues from our action or inaction, whether we want them to or not.