The Harvard College graduate of 2013 has experienced an epoch of social media revolution. Since 2004, a wave of interaction applications—Facebook, Gmail, Twitter, and others far too hip for me—have come to play a dramatic role in human interactions. But despite the rise of e-acquaintanceship, face-to-face contact remains the best tool for communicating the most complex ideas or the most sensitive thoughts, and that is why universities like Harvard and cities like Boston will continue to thrive.

When I came to Harvard 21 years ago, I was foolish enough to think that lecturing required two things: knowing your subject and being somewhat more entertaining than the usual college professor.  Twenty-one years later, I’ve come to realize how difficult it is to teach a complicated idea by talking or scribbling in chalk on the board. The riff on general equilibrium that I was sure would make everything clear to everyone actually didn’t work for anyone but me. I’ve learned hard concepts need to be presented repeatedly from different angles, even for the most brilliant students.

Indeed, it may be that the greatest talent that a teacher can have is the ability to hear through their students’ ears, to understand what they understand. Some of my colleagues seem born with this gift. I was not.

So I struggle, year after year, trying to figure out what aspects of my lectures are easily grasped and what parts are merely mind-numbing.  Talking to a hundred different students simultaneously is particularly challenging, because each student comprehends in a slightly different way.

But face-to-face teaching has one great advantage: Teachers get real-time feedback on how students are responding to our words. Humans have evolved over millions of years to have marvelous cues for communicating comprehension or confusion. Those cues are obvious when we’re in the same room, but not when lecturing via YouTube or by satellite. Most smart teenagers have spent years learning how to mask their rare moments of ignorance, but in lectures, the mask occasionally slips, which is lucky because teaching is much easier when students display what they aren’t understanding.

The face-to-face advantage in study groups, seminars and advising is also enormous.  A good seminar is an unpredictable, unfolding process that draws in the entire group.  I’ve never experienced the same energy or intellectual interaction in any electronic exchange.

Advising is delicate, because potentially painful criticism must be carefully modulated towards the individual student. Be too soft and the student misses the point. Be too hard and you make the student furious and resentful. Being in the same room allows better calibration. I haven’t always gotten advising right, but I would have been a far worse advisor if I only advised electronically.

The advantages of face-to-face teaching are mirrored in many other parts of life. If you need to criticize a colleague, do it in person. Praise is more valued when received face-to face. If you have a complicated idea to share with a partner, share it in the same room.  And don’t put anything in an email that you don’t want to see publicly pilloried in the blogosphere.

I’m not a Luddite. I strongly support edX. Technology has much to offer almost every course at Harvard, and long-distance learning has the potential to provide slightly lower quality education at a vastly lower cost. But I’m equally sure that the live, in-person, learning process isn’t going away. It will simply co-evolve with other means of communication, just as cities are also co-evolving with the internet.

Twenty-five years ago, cyber-seers and techno-prophets predicted that electronic interactions would make face-to-face contact and the cities that enable that contact obsolete. Why put up with the bother of working in New York, if you can just link in without wires?

But the past two decades have been good to cities, and good to America’s strongest universities. Universities and cities have much in common. They both connect humans and enable them to work together and learn from one another.

Our globalized, technological world has placed an ever higher premium on knowledge and innovation.   Human beings become smart by being around smart people. Every new idea is cobbled together from the thoughts that surround us. The best innovators are really superb at seeing what ideas are best to borrow from others.  We do learn in cyberspace, but we learn even more in person.  In a more complicated world, ideas are easier to lose in translation, which makes face-to-face contact even more valuable.

I don’t know what exactly a Harvard education will look like in 20 years, but I’m pretty sure of two things. New technologies will be even more important, but face-to-face learning will still be at the heart of the Harvard experience.

Edward L. Glaeser is the Fred and Eleanor Glimp Professor of Economics.