Thomas Friedman also poses the question and offers a way to answer it:

Excerpted from his worth-reading Postcards From Iraq:

" Readers regularly ask me when I will throw in the towel on Iraq. I will be guided by the U.S. Army and Marine grunts on the ground. They see Iraq close up. Most of those you talk to are so uncynical - so convinced that we are doing good and doing right, even though they too are unsure it will work. When a majority of those grunts tell us that they are no longer willing to risk their lives to go out and fix the sewers in Sadr City or teach democracy at a local school, then you can stick a fork in this one. But so far, we ain't there yet. The troops are still pretty positive.

So let's thank God for what's in our drinking water, hope that maybe some of it washes over Iraq, and pay attention to the grunts. They'll tell us if it's time to go or stay."