If graduates leave with ears and minds closed, the university has failed both the student and society. Photographer: David L Ryan/The Boston Globe via Getty Images
If graduates leave with ears and minds closed, the university has failed both the student and society. Photographer: David L Ryan/The Boston Globe via Getty Images

Universities lie at the heart of the American experiment in democracy. They are places where people of all backgrounds and beliefs can come to study and debate their ideas freely and openly. I’d like to talk with you about how important it is for that freedom to exist for everyone, no matter how strongly we may disagree with another’s viewpoint.

Tolerance for other people’s ideas and the freedom to express your own are inseparable values. Joined, they form a sacred trust that holds the basis of our democratic society. But that trust is perpetually vulnerable to the tyrannical tendencies of monarchs, mobs and majorities. And lately, we have seen those tendencies manifest themselves too often, both on college campuses and in our society.

I think both Harvard and my own city of New York have been witnesses to this trend.

First, New York City. Several years ago, as you may remember, some people tried to stop the development of a mosque a few blocks from the World Trade Center site. It was an emotional issue, and polls showed that two-thirds of Americans were against a mosque being built there. Even the Anti-Defamation League -- widely regarded as the country’s most ardent defender of religious freedom -- declared its opposition to the project.

The opponents held rallies and demonstrations. They denounced the developers. And they demanded that city government stop its construction. That was their right -- and we protected their right to protest. But we refused to cave in to their demands.

The idea that government would single out a particular religion and block its believers -- and only its believers -- from building a house of worship in a particular area is diametrically opposed to the moral principles that gave rise to our nation and the constitutional protections that have sustained it.

Our union of 50 states rests on the union of two values: freedom and tolerance. And it is that union of values that the terrorists who attacked us found most threatening. To them, we were a God-less country. In fact, there is no country that protects the core of every faith and philosophy -- free will -- more than the United States.

That protection, however, rests upon our constant vigilance.

It is up to us to ensure that equality under the law means equality under the law for everyone. If you want the freedom to worship as you wish, to speak as you wish and to marry whom you wish, you must tolerate my freedom to do so -- or not do so -- as well. You may find my actions immoral or unjust, but attempting to restrict my freedoms, in ways that you would not restrict your own, leads only to injustice.

Throughout history, those in authority have tried to repress ideas that threaten their power, their religion, their ideology or their re-election chances.

That was true for Socrates and Galileo; it was true for Nelson Mandela and Vaclav Havel; and it has been true for Ai Weiwei, Pussy Riot and the kids who made the “Happy” video in Iran.

We cannot deny others the rights and privileges that we demand for ourselves; that is true in cities, and it is no less true at universities, where the forces of repression appear to be stronger now than they have been since the 1950s.

There is an idea floating around college campuses -- including here at Harvard -- that scholars should be funded only if their work conforms to a particular view of justice. There’s a word for that idea: censorship. And it is just a modern-day form of McCarthyism.

In the 1950s, the right wing was attempting to repress left-wing ideas. Today, on many campuses, it is liberals trying to repress conservative ideas, even as conservative faculty members are at risk of becoming an endangered species.

Perhaps nowhere is that more true than here in the Ivy League. In the 2012 presidential race, 96 percent of all campaign contributions from Ivy League faculty and employees went to Barack Obama. That statistic, drawn from Federal Election Commission data, should give us pause -- and I say that as someone who endorsed President Obama. When 96 percent of faculty donors prefer one candidate to another, you have to wonder whether students are being exposed to the diversity of views that a university should offer. Diversity of gender, ethnicity and orientation is important. But a university cannot be great if its faculty is politically homogenous.

In fact, the whole purpose of granting tenure to professors is to ensure that they feel free to conduct research on ideas that run afoul of university politics and societal norms. When tenure was created, it mostly protected liberals whose ideas ran up against conservative norms.

Today, if tenure is going to continue to exist, it must also protect conservatives whose ideas run up against liberal norms. Otherwise, university research will lose credibility. A liberal arts education must not be an education in the art of liberalism.

This spring, it has been disturbing to see a number of college commencement speakers withdraw, or have their invitations rescinded, after protests from students and -- to me, shockingly -- from senior faculty and administrators who should know better.

It happened at Brandeis, Haverford, Rutgers and Smith. Last year, it happened at Swarthmore and Johns Hopkins. In each case, liberals silenced a voice and denied an honorary degree to individuals they deemed politically objectionable.

As a former chairman of Johns Hopkins, I believe that a university’s obligation is not to teach students what to think, but to teach students how to think. And that requires listening to the other side, weighing arguments without prejudging them, and determining whether the other side might actually make some fair points.

If the faculty fails to do this, then it is the responsibility of the administration and governing body to step in and make it a priority. If they do not, if students graduate with ears and minds closed, the university has failed both the student and society. If you want to know where that leads, look no further than Washington.

In Washington, every major question facing our country is decided. Yet the two parties decide these questions not by engaging with one another, but by trying to shout each other down, and by trying to repress and undermine research that runs counter to their ideology. The more our universities emulate that model, the worse off we will be as a society.

An example: For decades, Congress has barred the Centers for Disease Control from conducting studies of gun violence, and recently Congress also placed that prohibition on the National Institutes of Health.

This year, the Senate has delayed a vote on President Obama’s nominee for surgeon general -- Vivek Murthy, a Harvard physician -- because he had the audacity to say that gun violence is a public health crisis that should be tackled.

Let’s get serious: When 86 Americans are killed with guns every day, and shootings regularly occur at our schools and universities, including last week’s tragedy in Santa Barbara, California, it would be almost medical malpractice to say anything else.

But in politics -- as it is on too many college campuses -- people don’t listen to facts that run counter to their ideology. They fear them. And nothing is more frightening to them than scientific evidence.

Earlier this year, the state of South Carolina adopted new science standards for its public schools -- but the state legislature blocked any mention of natural selection. It was kind of like teaching economics without mentioning supply and demand.

Just as members of Congress fear data that undermines their ideological beliefs, these state legislators fear scientific evidence that undermines their religious beliefs. And if you want proof of that, consider this:

An 8-year-old girl in South Carolina wrote to members of the state legislature urging them to make the woolly mammoth the official state fossil.

The legislators thought it was a great idea, because a woolly mammoth fossil was found in the state in 1725. But the state Senate passed a bill defining the woolly mammoth as having been “created on the sixth day with the other beasts of the field.”

Unfortunately, the same elected officials who put ideology and religion over data and science when it comes to guns and evolution are often the most unwilling to accept the scientific data on climate change.

Now, don’t get me wrong: Scientific skepticism is healthy. But there is a world of difference between scientific skepticism that seeks out more evidence and ideological stubbornness that shuts it out.

Given the general attitude of many elected officials toward science education, it’s no wonder that the federal government has abdicated its responsibility to invest in scientific research, much of which occurs at our universities.

Today, federal spending on research and development as a percentage of gross domestic product is lower than it has been in more than 50 years, which is allowing the rest of the world to catch up -- and even surpass -- the U.S. in scientific research.

We can't risk becoming a country that turns its back on science, or on each other. And you graduates must help lead the way.

On every issue, we must follow the evidence where it leads and listen to people where they are. If we do that, there is no gridlock we cannot break, no compromise we cannot broker, no problem we cannot solve.

(Michael R. Bloomberg, the former mayor of New York City, is the founder and majority owner of Bloomberg LP, the parent company of Bloomberg News. This article is adapted from a commencement speech given today at Harvard University.)

To contact the editor responsible for this article: David Shipley at davidshipley@bloomberg.net.