Good afternoon. My remarks at this moment in our Commencement rituals are officially titled a "Report to the Alumni." The first time I delivered them, in 2008, I was the only obstacle between all of you and J.K. Rowling. I looked out on a sea of eager children, costumed Dumbledores, and Quidditch brooms waving impatiently in the air. Today, you await Mark Zuckerberg, whose wizardry takes a different form, one that has changed the world, and although he doesn't seem to have inspired an outbreak of hoodies, we certainly do have some costumes in this audience today. I see we are now handing out blankets.

   This is a day of joy and celebration, of happy endings and new beginnings, of families and friends, of achievements and hopes. It is also a day when we as a university perform our most important annual ritual, affirming once again the purposes that animate us and the values that direct and inspire us.

I want to speak today about one of the most important – and in recent months, most contested – of these values. It is one that has provoked debate, dissent, confrontation, and even violence on campuses across the country, and one that has attracted widespread public attention and criticism.

I am, of course, talking about issues of free speech on university campuses. The meaning and limits of free speech are questions deeply embedded in our legal system, in interpretations of the First Amendment and its applications. I am no constitutional lawyer, indeed no lawyer at all, and I do not intend in my brief remarks today to address complex legal doctrines. Nor, clearly, can I in a few brief minutes take on even a fraction of the arguments that have been advanced on this issue. Instead, I speak as one who has been a university president for a decade in order to raise three questions:

First: Why is free speech so important to and at universities?

Second: Why does it seem under special challenge right now?

And, third: How might we better address these challenges by moving beyond just defensively protecting free speech – which, of course, we must do – to actively and affirmatively enabling it and nurturing environments in which it can thrive?

So first: Why is free speech so important to and at universities? This is a question I took up with the newly arrived first-year students in the College when I welcomed them at Convocation last fall. For centuries, I told them, universities have been environments in which knowledge has been discovered, collected, studied, debated, expanded, changed, and advanced through the power of rational argument and exchange. We pursue truth unrelentingly, but we must never be so complacent as to believe we have unerringly attained it. Veritas is inspiration and aspiration. We assume there is always more to know and discover so we open ourselves to challenge and change. We must always be ready to be wrong, so being part of a university community requires courage and humility. Universities must be places open to the kind of debate that can change ideas and committed to standards of reason and evidence that form the bases for evaluating them.

Silencing ideas or basking in intellectual orthodoxy independent of facts and evidence impedes our access to new and better ideas, and it inhibits a full and considered rejection of bad ones. From at least the time of Galileo, we can see how repressing seemingly heretical ideas has blinded societies and nations to the enhanced knowledge and understanding on which progress depend. Far more recently, we can see here at Harvard how our inattentiveness to the power and appeal of conservative voices left much of our community astonished – blindsided by the outcome of last fall's election. We must work to ensure that universities do not become bubbles isolated from the concerns and discourse of the society that surrounds them.

Universities must model a commitment to the notion that truth cannot simply be claimed, but must be established – established through reasoned argument, assessment, and even sometimes uncomfortable challenges that provide the foundation for truth. The legitimacy of universities' claim to be sources and validators of fact depends on our willingness to actively and vigorously defend those facts. And we must remember that limiting some speech opens the dangerous possibility that the speech that is ultimately censored may be our own. If some words are to be treated as equivalent to physical violence and silenced or even prosecuted, who is to decide which words? Freedom of expression, as Justice Oliver Wendell Holmes famously said long ago, protects not only free thought for those who agree with us but freedom for the thought we hate. We need to hear those hateful ideas so our society is fully equipped to oppose and defeat them.

Over the years, differences about the implementation of the University's free speech principles have often provoked controversy. And we haven't always gotten it right. As long ago as 1939, an invitation from a student group to the head of the American Communist Party generated protest and the invitation was ultimately canceled by the Corporation. Bertrand Russell's appointment as William James Lecturer just a year later divided the Corporation, but President Conant broke the tie and Russell came. Campus conflicts over invited speakers are hardly new.

Yet the vehemence with which these issues have been debated in recent months, not just on campuses but in the broader public sphere, suggests there is something distinctive about this moment. Certainly, these controversies reflect a highly polarized political and social environment – perhaps the most divisive since the era of the Civil War. And in these already fractious circumstances, free speech debates have provided a fertile substrate into which anger and disagreement could be planted to nourish partisan outrage and generate media clickbait. But that is only a partial explanation.