All knowledge, including the fruits of our research, is not the birthright of a nation, but a gift to the world. As America's first University, Penn embraces this truth. We welcome students and scholars from around the globe.

While they come to Penn to pursue opportunity and excellence in their chosen fields, they dramatically expand our body of knowledge, raise our cultural awareness, and invariably make spectacular contributions to the world.

Take Ahmed Zewail. He came from Egypt to Penn a generation ago as a graduate student. After earning his doctorate in chemistry at Penn, Dr. Zewail unraveled fundamental chemical processes and developed ultrafast laser techniques for observing chemical reactions in real time. In 1999, Dr. Zewail won the Nobel Prize in Chemistry.

Fan Chung is another exceptional scholar with strong Penn connections. A native of Taiwan, Dr. Chung earned her doctorate here in mathematics in 1974, and went on to become a world-class researcher, teacher, and scientist in both the academic and corporate world. Her groundbreaking work in spectral graph theory, discrete geometry, algorithms, and communications networks has won her numerous honors and awards. In the tradition of Franklin, she is passionate about teaching students to connect the mathematics learned in the classroom to contemporary problems and challenges.

Penn continues to court and attract preeminent scholars from all over the world, and they invariably light an intellectual spark on campus.

This past year, we welcomed political scientist Brendan O'Leary from the London School of Economics into our community of scholars, and he more than lived up to his reputation as a riveting teacher, a premier authority on ethnopolitical conflict, and a public intellectual of the first rank. We're delighted that Dr. O'Leary has signed on to stay with us for the next three years, and we hope he'll make Penn his permanent academic home.

Drs. Zewail, Chung, and O'Leary are just three of the thousands of international students and scholars who have invigorated the Penn campus and community, and many of them are receiving Penn diplomas today.

We would like to believe that the virtues and value of internationalism and academic freedom are self-evident. Yet, some argue that in order to protect our freedoms and pluralistic society, we must close our doors to international students and scholars.

To be sure, homeland security will require greater scrutiny at our borders, and greater screening of those who wish to come here. But we must protect the multiplicity of cultures and peoples that makes us strong. It is true, as Albert Einstein famously remarked during another period of world crisis, that "The significant problems we face cannot be solved by the same level of thinking that created them."

We must reexamine and be prepared to abandon old approaches to problems like disease, poverty, and terrorism that have proven ineffective. But we cannot solve our problems by riding herd on creativity, competition, enterprise, or dissent.

We need new thinking, not wishful thinking.

We need to embrace a culture of trial and error, not a regime of risk avoidance.

We need the room to explore, experiment, and create.

We need a constant infusion of brainpower from all over the world to be deployed to tackle the world's most complex questions.

We need freedom, and we need you, Penn's highly resilient and outstanding graduates, to use that freedom to raise the level of thinking in business, government, the arts, science, and your individual professions.

Draw on your knowledge and Penn education to inform the debate over the war on terrorism. Find a way to educate the public on the values and truths of science.

An alarming knowledge gap is growing between the nation's scientists who are on the brink of many life-saving discoveries and advances, and the nation's policymakers who have the power to promote or stifle scientific progress. So it's especially important for you to find an effective way to speak the truths of science to those in power.

Continue also to cultivate diversity in your cultural fare, your work habits, and in your social life. Bring to your businesses, your professions, and your careers a passionate integrity that tips the culture firmly into the ethical zone.

And by all means, share the gifts of your unique intelligence and creativity with the world.

We all know that Einstein's Theory of Relativity revolutionized physics and changed the world. But we sometimes forget that Einstein arrived at his immortal theory by unconventional means. Because he viewed time much differently than his supposedly more learned peers, he had the vision to see the workings of the Universe in an entirely new way.

Within each of you lies the seed of an idea or vision that, like Einstein's Theory of Relativity, can change the world, but only if you have the courage to cultivate it.

You join a select group of men and women who have taken an adventurous voyage of discovery at Penn. As the heirs of Franklin, each of you now is a public-spirited citizen of the world.

So I expect to see one or two of you in the Oval Office, a few of you accepting Nobel Prizes, a lot of you prospering, and all of you leading full lives that bring joy and meaning to yourselves, credit to Penn, and lasting benefits to humanity.

I am so very proud of you.