“Cities are the absence of physical space between people and companies. They are proximity, density, closeness. They enable us to work and play together, and their success depends on the demand for physical connection.” Glaeser, Edward. Triumph of the City: How Our Greatest Invention Makes Us Richer, Smarter, Greener, Healthier, and Happier.

Consider this statement and its many variants: “With information travelling at the speed of light, physical distances shrink into insignificance.” But facts are obstinate things. In the United States, 81.6% of the population is classified as “urban” (subject to the uncertainty of that classification), while over the past five years, the annual rate of urbanization is 1.02%. Globally, 54% of the population lives in urban areas – a figure that is projected to grow to 66% by the year 2050. Why, when people, especially highly educated “creative class” workers, can choose to live anywhere, are they still moving to cities?

In any event, the things that were supposed to minimize the effects of distance have not created a substitute for the lovely chaos of cities. And not just cities, in the many forms in which we now know them, but cities that by accident or design have thrust their inhabitants into disproportionately small spaces. The most interesting cities in my part of the world (the Atlantic Coast of the United States) are cities whose geographies demand density. The island of Manhattan, the peninsula of Charleston, and the back bay of Boston all ensured that those who wanted to be close to the action were quite close indeed.

Edward Glaeser argues that “communication complexity” explains the continued advantages of physical proximity over any virtual community. Human communication involves countless nonverbal subtexts (body language, intonation, intensity of attention) that do not attach to virtual communication. I think it more important that the most productive and creative exchanges happen in random, non-scripted, accidental moments of connection. Those moments, in turn, happen when people are just hanging around together.

Cass Sunstein makes a point I consider related; through self-selection, virtual communities are likely to become ideologically homogeneous, and therefore are at least potentially antidemocratic. Even those communities that are not explicitly ideological (for example, those based on shared interests, hobbies, taste in music) tend to become homogenous in other ways – demographic, economic, ethnic. Population density, on the other hand, almost invariably forces us to interact with people who are quite different from us indeed. And when those interactions become unwelcome, it’s much harder to physically leave a city than it is to “unsubscribe” from a virtual community. The city is a more democratic place than can be found anywhere on a computer screen.

Questions arise. If density is the key to human flourishing, how do we encourage it? What is the role of government in fostering it? Are there workable solutions to the inevitable frictions created by density? Perhaps most pressingly, what is the relationship between urbanization and wealth inequality? If we admit, even celebrate, the rise of the “creative class” who increasingly drive the migration to density, what shall we do about those left out or behind?