In short, the problem now across the Arab East is not just poison gas, but poisoned hearts. Each tribe or sect believes it is in a rule-or-die struggle against the next, and when everyone believes this, it becomes self-fulfilling.

That means Syria and Iraq will both likely devolve into self-governing, largely homogeneous, ethnic and religious units, like Kurdistan. And, if we are lucky, these units will find a modus vivendi, as happened in Lebanon after 14 years of civil war. And then maybe, over time, these smaller units will voluntarily come together into larger, more functional states.

I still believe our response to Assad’s poison gas attack should be “arm and shame,” as I wrote on Wednesday. But, please do spare me the lecture that America’s credibility is at stake here. Really? Sunnis and Shiites have been fighting since the 7th century over who is the rightful heir to the Prophet Muhammad’s spiritual and political leadership, and our credibility is on the line? Really? Their civilization has missed every big modern global trend — the religious Reformation, democratization, feminism and entrepreneurial and innovative capitalism — and our credibility is on the line? I don’t think so.