Jonah Lehrer:

City life isn't easy.

Now scientists have begun to examine how the city affects the brain, and the results are chastening.

Just being in an urban environment, they have found, impairs our basic mental processes. This research arrives just as humans cross an important milestone: For the first time in history, the majority of people reside in cities.

From the archive:

I’m not thinking the way I used to think.

Great cities have always been hard to manage. Like other complex systems, they grow spontaneously but then demand more management and investment if they are to avoid decay and disintegration. A time comes in the lives of big cities when the need for regulation and rational allocation of space, money, and other resources prevails over impulsive processes.

Consider:

Government policies -- from as early as the 1890s -- subsidized the spread of cities and fueled a chronic nationwide dependence on cars and roadbuilding, with little regard for expense, efficiency, ecological damage, or social equity.

Finally, Stewart Brand:

What the world has now is new cities with young populations and old cities with old populations. How the dialogue between them plays out will determine much of the nature of the next half century. The convergence of the two major trends, globalization and rampant urbanization, means that all cities are effectively one city now.