It can sometimes take a tragedy to reveal a truth.

Who does not remember where they were on Sept. 11 when they heard that the towers had come down? But terrible times also can provide insight that might otherwise never come.

In 2001, I was teaching in Chicago. My main break from work was frequent participation in a daily pickup soccer game that I stumbled onto soon after arriving in town. It was a virtual United Nations, with players from Argentina, Russia, Germany, Iran, Italy, Turkey, Georgia, Brazil, Poland, Korea, China and Mexico.

I was the only non-immigrant who was a regular, and each group had its own style. Most of the South Americans and Southern Europeans were finesse players. The Eastern Europeans were brawlers. You not only didn’t intentionally foul them, no matter what the game situation, you played them loose to avoid even risking an unintentional foul, and in the space that that created lay their tactical advantage. The Arabs had a nicely balanced game. The Asians had a balanced game and doggedness. I had only doggedness.

In our normal routine, we would warm up and chat in small groups until, at the appointed time, the best players present — usually a middle-age Argentine and a younger Pole — would quickly point out teams and we were off.

But on the day after 9/11, things were different. As people collected at the field, they were quiet. At the appointed time, apparently by prior arrangement, the players came to the center of the field and stood in a circle.

They went around the circle, each in turn saying something, not about the attacks the day before but about what the country meant to them. The common theme was opportunity and freedom, with each person offering a specific example from his own life and how it had changed. Some were less articulate, some more articulate, some downright eloquent.

I came late in the circle. I had not seen this coming and didn’t know quite what to say. I didn’t have a changed-life story. I saw some skeptical looks, as if they were used to Americans not appreciating what they had. I finally said only that I could not imagine there was another country in the world where a circle like this would be taking place, and how lucky I felt to be here.

The exercise had touched me, and I was emotional.

I have thought about that circle many times in the intervening years, always getting a little misty. The memory colors my judgment on a wide variety of issues, including immigration, patriotism and American exceptionalism.

I wonder whether there ever has been another country in the history of the world to which so many people from so many countries have so badly wanted to go and, once there, have been so devoted.

Paul H. Robinson is a professor of law at the University of Pennsylvania and the co-author, with Sarah Robinson, of the coming book, “Human Rules: Modern Lessons from Pirates, Eskimos, Lepers & Survivors.”