To the long list of threats to the quality of an American university education, we can now add another: the rush into online instruction. Universities across the country are under increasing pressure to offer more of their courses over the Internet. The University of California, where I teach, has started offering for-credit online undergraduate courses this year.
In theory, moving online is a win-win for all involved. Students receive instruction at the locations of their choosing, courses become more accessible to working students who can eliminate the overhead of commuting to class, cash-strapped universities broaden their reach and revenue base, and professors can earn extra compensation for putting their courses online.

But amid the enthusiasm for all that is gained, it is also important to look at what is lost when the classroom experience is piped through the Internet and delivered on a screen. The Internet is very efficient at conveying words and images from one place to another. But good university teaching is much more than that.

Teaching in the truest sense is what occurs when a committed instructor gets in a room with a group of equally committed students and engages them in an interactive, probing and challenging treatment of a subject. A good lecture or seminar has its foundation in words but gains its texture and flow from countless other subtle cues and interactions in the classroom. These include the body language of the students that an alert instructor will observe and use in modulating the pace and content of the discussion, the pauses and inflections in student questions that would escape capture by a microphone, and the dynamism that occurs because each student, sitting among different neighbors at a unique location in the room, experiences and engages with the class slightly differently.

A course is also made effective by the unscripted interactions that occur as students gather before and after the class, and by the simple fact that the physical act of getting to class requires at least some investment of time and energy. In short, attending a well-run class in person is immersive and engaging in a way that far exceeds anything that consumer technology can possibly hope to deliver now or in the foreseeable future.

I'll admit that there's a certain attraction to the idea of moving to Maui and teaching all my classes from the comfort of a video camera-equipped home office. In fact, on a small number of occasions over the years, I have lectured by live videoconference when an unavoidable business trip left me the choice between teaching by videoconference or not at all. Each time I do this I am struck by the near miracle of reaching across time zones and miles to see and hear my students in a sunlit classroom in California. I speak and write on the board; they take notes and ask questions. Business as usual.

But when the lecture ends, a button is pushed, and jarringly I am suddenly somewhere else — a campus in the evening on the East Coast, or a nearly empty building near midnight somewhere in Europe. And I always feel a pang of guilt because I know, and my students know, that a class taught by videoconference is a distant second choice to the here-and-now presence of a lecture, properly delivered, by a real person standing in front of them.

The national trend toward online university instruction has been bolstered by a Department of Education-funded report that analyzed nearly 100 studies and concluded that online instruction, in the words of the report's lead author, "actually tends to be better than conventional instruction."

Depending on how narrowly one defines "better," that may be true. Under certain conditions it undoubtedly is true — for example, for the working student who cannot travel to class and for whom online education opens a whole new world of previously inaccessible options. For these students, universities can and should work to create appropriate frameworks and programs to use online instruction to broaden their reach.

But policymakers, university teachers and administrators should acknowledge that scientific studies and budget pressures notwithstanding, something is lost when the classroom experience becomes virtual. As we strive to educate our university students in an increasingly competitive global economic climate, among the many costly and complex measures that are on the table for improving their educational experience, here's one that is refreshingly simple: Show up.

Instructors owe it to their students to be there in the classroom, and students owe it to themselves — and to the rest of us — to do their best to be there as well.