On Tuesday the 18th, one week after the tragedies in New York and Washington, I stood at a Beacon Street crosswalk waiting for the light to change. On the far side of the street I caught sight of a woman, who, at any other time of the year, would have been totally unremarkable. She wore a pair of jeans, a cotton blouse, a backpack, a blue headscarf. Her simple hijab told me and every one else on the street that she was a follower of Islam.

Now, I know what you're thinking. I stared at this woman because she's Muslim and overnight, though we hate to admit it, all our Muslim neighbors became suspects. That's partly true, but really caught my attention was the large red, white, and blue button she wore on her blouse, and the small American flag she held in her hand.

I should have easily accepted her as a patriot, a proud American showing her support for the nation. But that's not what she was. She gave herself away by not making eye contact with anyone on the street, and gripping that little flag so tight that her knuckles went white. She was scared; and she carried the Stars and Stripes with her for protection.

No other nation in the world rallies around its flag the way we Americans do. It's the most potent symbol the United States has - we don't have a crown or an emperor to celebrate, and presidents come and go every four years or so. But the flag - I don't know a single person who isn't moved in some way when seeing it atop a building, or when draped over a coffin, or when happily waved by a child's hand.

But I wondered: If the flag is a symbol for everything that's good about America, why would my neighbor carry it with her in fear?

Any symbol of such power begs the questions: What do those colors really mean? And, how is that symbol really used?

The flag is both a defensive and offensive symbol at once; a simultaneous source of pride and prejudice in the hands and hearts of those who hold it. Unfortunately, there have been many times - almost too many to count - when the Stars and Stripes hasn't been used to drape the nation in a sense of solidarity. It's been used to spill blood.

And it's happened, right here in Boston. There's a very famous photograph, taken during the anti-busing riots in 1974. On the right, there's a black Bostonian jumping back, like he's trying to dodge something. And on the left, there's his white neighbor, lunging at him with the tip of a metal staff - flag unfurled - using Old Glory's pointed pole like a deadly spear to plunge into the black American's stomach.

There's a tense duality in our nation's flag. Is it a symbol capable of uniting a nation in peace and hope? Or is it one of the most powerful rhetorical weapons of mass destruction, used to justify violence both here and abroad? We have to choose.

I'm proud to say that most of us choose the healing power of the flag. But of the manifold images we've seen since September 11th, two will stay with me for the rest of my life. One is the sight of hellfire spewing from the top of the World Trade Center, like the devil's acid breath. The other is that of my Muslim neighbor. One American patriot clutching Old Glory in her hand - the shield of freedom - to protect herself from fellow citizens parading the very same colors.