President Obama's speech in New Orleans on Sunday, commemorating the fifth anniversary of Katrina, didn't have one clear message so much as two. The city has rebuilt and, in some ways, rebuilt itself into something better. But a lot of work, too much work, remains unfinished. If you read my dispatches from New Orleans two weeks ago, then you know that was the impression I, too, took away.

One question that Obama didn't address was "why"--as in "why bother"? From the first days after the storm, people began asking whether it was time just to give up on New Orleans. For all of the progress the city has made, it still sits below sea level, in a part of the country particularly vulnerable to hurricanes. A direct-hit, category five storm is going to level, or at least inundate, the city all over again. A lesser storm might do the same if the new levees and pumps don't succeed, or if the wetlands continue to deteriorate.

You can answer this question with sentimentality: New Orleans has a special place in our artistic, literary, and musical culture. To quote Bruce Springsteen, it is "hallowed ground." You can also answer this question economically. The Port of New Orleans is one of the nation's busiest and, sitting where it does on the Mississippi River, and the cost of rebuilding that infrastructure elsewhere might be larger than keeping it in New Orleans.

But there's another answer--one I got from Mark Schleifstein, the veteran expert on hurricane and the environment at the Times-Picayune. I put the question to him: Shouldn't we just give up on New Orleans, given its vulnerability? Sure, he said. He could see that. But then shouldn't we also give up on Charleston, Houston, and the hundred miles or so that stretch from West Palm Beach down to South Miami? What about Southern California and the San Francisco Bay Area, which sit astride major fault lines?

I did have one more thing to say about New Orleans, Katrina, and how it should change (or not change) the way we think about government activism. I'll leave that for another item. But if you want to learn more, I'd recommend two books, also by Times-Picayune correspondents. Breach of Faith, by Jed Horne is, as far as I know, the most accurate and comprehensive overview of the story, covering everything from the storm itself to the levee failures to the disaster relief. One Dead in the Attic, by Chris Rose, is a collection of newspaper columns that the author wrote in the two years following the storm. Both are great sources of information. Both are also great reads.

Finally, for those of you who missed my initial dispatches, here they are:

Introduction: New Orleans five years later

How government failed the city, again

The nation's largest experiment in education reform

Can the city survive another Katrina?

Why everybody in New Orleans is an activist