It was right here，in the waters around us，where the American experiment began. As the earliest settlers arrived on the shores of Boston and Salem and Plymouth，they dreamed of building a City upon a Hill. And the world watched，waiting to see if this improbable idea called America would succeed.
For over two hundred years，it has. Not because our dream has progressed perfectly. It hasn’t. It has been scarred by our treatment of native peoples，betrayed by slavery，clouded by the subjugation of women，wounded by racism，shaken by war and depression.
Yet，the true test of our union is not whether it’s perfect，but whether we work to perfect it. Whether we recognize our failings，identify our shortcomings，and then rise to meet the challenges of our time.
And so we’ve broadened the American family by winning civil rights and voting rights for women and then African Americans；by choosing to welcome waves of new immigrants to our shores.
We’ve pushed the boundaries of opportunity by providing free education for our children and health care for our seniors and our poor；and we’ve won bargaining rights and wage hikes and retirement security for our workers.
None of this progress happened on its own. Much of it seemed impossible at the time. But all of it came about because ordinary men and women had faith that here in America，our imperfect dream could be perfected.
Now，there may be some who doubt that much has changed - those who doubt that things are better today than they were yesterday. To them I say take a look at this class of 2006.
More than half of you represent the very first member of your family to ever attend college. In the most diverse university in all of New England，I look out at a sea of faces that are African-American and Hispanic-American and Asian-American and Arab-American. I see students that have come here from over 100 different countries，believing like those first settlers that they too could find a home in this City on a Hill - that they too could find success in this unlikeliest of places.
All of this has occurred in the midst of a city where No Irish Need Apply signs once hung from stores. All of this in a city where，just thirty years ago，buses of black students were pelted with rocks as they pulled into schools in South Boston；where the Red Sox were once the team who refused to sign the great Jackie Robinson.
But the problem isn’t that we’ve made progress. The problem is that progress isn’t good enough. There is more work to be done，more justice to be had，more barriers to break. And now it’s your generation’s turn to bring these changes about.
The last century was undoubtedly an American century. Our victory over fascism liberated millions. At home，we built a shared prosperity that created the largest middle-class in history. Ours was a nation of liberators；of free people；of prosperous people - and the world took notice.
But today，just a few years into the twenty-first century，we already find ourselves in a different and precarious position. As revolutions in communications and technology have broken down barriers across the world，it has given more power to both our competitors and our enemies.
No longer can we assume that a high-school education in Boston is enough to compete for a job that could easily go to a college-educated student in Bangalore or Beijing. No more can we count on employers to provide health care and pensions and job training when their bottom-lines know no borders. Never again can we expect the oceans that surround America to keep us safe from attacks on our own soil.
So what does this mean for you？What role will you play in meeting these challenges？
I do not pretend to have the answers. Each of you will have to discover your own. But perhaps I can offer a few suggestions that may be useful along the way.
First，take risks. When I was on the brink of graduating from college，I had this crazy idea that I wanted to be a community organizer and work in low-income neighborhoods.
My mother and grandparents thought I should go to law school，and my friends were all busy applying for jobs on Wall Street. But I went ahead and wrote letters to every organization in the country that I thought was working to empower low-income people. And finally，this small group of churches on the south side of Chicago wrote back and offered me a job helping them deal with the consequences of steel plants that had closed and put thousands out of work.
The churches didn’t have much money - so they offered me a grand sum of 12，000 a year plus 2，000 to buy a car. So I bought a beat up old car，packed up my belongings，got out a map，and started driving west to Chicago - a place I had never been and where I didn’t know a living soul.
About halfway between New York City and Chicago，I stopped for the night in a small town in Pennsylvania whose name I no longer remember. I found a motel that looked cheap and clean，I pulled into the driveway，and went to the counter，where there was an old guy doing crossword puzzles.
I asked him for a room，and as he was filling out my information，he asked me where I was headed. I said I was going to Chicago，and I told him I was going there to work as a community organizer. And he looked at me and he said，“You know，you look like a nice clean-cut young man，and you’ve got a nice voice. So let me give you a piece of advice - forget this community organizing business. You can’t change the world，and people won’t appreciate you trying. What you should do is go into television broadcasting. I’m telling you，you’ve got a future.”