Earlier this month, Harvard University president Lawrence Summers suggested that male-female differences in math and science achievement might have biological causes. Angry professors in his audience walked out, alumni threatened to withhold donations, and Mr. Summers was forced to issue several solemn apologies.
So let's suppose that he had proposed a biological basis for sexual orientation, not for math and science ability. Would anyone have objected?
Of course not. Watching this episode unfold, you can understand why so many people hold university professors in contempt these days. They think we're smug, arrogant, and intellectually dishonest.
And here's a little secret: They're right.
Most professors - myself included - are zealous proponents of equal rights for homosexuals. Some Christian conservatives claim that gays can be converted into straights through a combination of religion and therapy. So good-hearted academics often embrace the possibility of a so-called gay gene, if only to rebut this right-wing attack.
When it comes to gender, however, biological explanations are taboo among my academic colleagues. For many centuries, men have justified the lowly status of women by arguing that the female intellect is inherently inferior. Lest professors stand accused of promoting discrimination, then, we must assert that every observable gender difference comes from our environment rather than from our selves.
But this dogma - indeed, every dogma - runs counter to the true spirit of a university. To advance knowledge, we need to examine the fullest range of evidence and explanation. And we must acknowledge that people of equal intellect and good will can reason from the same facts to different conclusions.
That's precisely the spirit that Summers's critics seem to have lost. He simply asked them to consider the possibility that biology caused some male-female achievement differences. Clearly, though, their minds are closed to any theory that differs from their own.
One can only imagine how the professors who condemned Summers would react if one of their own students made a similar suggestion in class. Actually, you don't have to imagine it. You can just read about this season's other big academic controversy, involving professors of Middle East studies at Columbia University.
According to a student-made documentary film, several of the professors have "intimidated" Jewish students by making anti-Israel comments. Most other faculty members have leapt to the professors' defense, claiming that the charges threaten "academic freedom."
Never mind that few of these folks rallied to defend the academic freedom of Lawrence Summers, or of people who might agree with him. The real issue is not whether the Columbia professors should be free to voice their opinions - of course they should be - but whether their students feel free to disagree with them.
Clearly, many students at Columbia don't. One student who had served in the Israeli army says that a professor asked him how many Palestinians he had killed, a charge that the professor vehemently denies. Others complain that faculty members routinely denounce Israel as "racist," which makes Jewish students particularly uncomfortable.
Of course, education should make students feel "uncomfortable." It should challenge their most basic beliefs, opinions, and assumptions. The problem arises when professors insist that students change their beliefs, especially as a condition for success in a class. Professors have every right to call Israel racist, in other words, but absolutely no right to judge students based on whether they agree.
That's what some students say has happened at Columbia, and they're hardly alone. According to a recent survey commissioned by the American Council of Trustees and Alumni, 3 out of 10 students at the nation's 50 top colleges believe they must conform to their professors' political opinions in order to get a good grade.
How can we arrest this troubling trend? A good first step might be a frank admission of professorial fallibility. We know more than our students, most of the time, but we don't have all of the answers. Do different male-female achievement levels in science and math have a biological component, as Lawrence Summers suggested?
I rather doubt it, myself, but I'm really not sure. Shame on us for pretending that we are.
• Jonathan Zimmerman teaches history and education at New York University. He is the author of 'Whose America: Culture Wars in the Public Schools.'