Harvard economics professor Edward Glaeser brings new life and controversy to the study of urban areas with his book Triumph of The City: How Our Greatest Invention Makes Us Richer, Smarter, Greener, Healthier, and Happier (2011). The 2011 Penguin Books edition is the subject of this guide.

Glaeser amasses evidence from his own research and elsewhere to prove the critical importance of cities to the progress of humanity. His thesis is that the many personal interconnections that take place in dense metropolises generate good ideas that lead to greater economic productivity, better opportunities for the poor, more creativity in arts and entertainment, and an environmentally greener way of life than is possible in rural or suburban areas.

Since ancient Athens, cities have been idea factories. Today, the leading urban centers of innovation—Bangalore in India, Silicon Valley in California, as well as New York, Boston, London, Hong Kong, and Singapore—attract educated workforces and lots of small, innovative businesses where ideas translate into new goods and services. Once-great manufacturing cities like Detroit became too dependent on a few large industries and were unable to remake themselves when factories no longer needed masses of laborers. Some, like New York and Boston, managed comebacks by reconfiguring themselves as centers of innovation, where person-to-person interactions proved vital to the growth of productivity. Key to this makeover is education: A well-schooled workforce is more creative and prosperous.

Cities worldwide attract the poor because urban centers offer better opportunities than rural regions. In a well-functioning city, poverty is a sign of success (the urban poor tend to rise out of poverty; they’re replaced by newcomers who follow in their footsteps). In urban centers where the poor become ensnared and unable to move up, the problem usually lies with bad governance. The best things city leaders can do are provide clean water, sanitation, functioning transit systems, competent policing, and good schooling. In Western countries, disease and crime have come down over the past century, and those cities are now safer than the countryside.

Arts and entertainment thrive in the crowded give-and-take of city life. Enticing arts scenes and buzzing nightlife are selling points for cities that wish to attract the best-educated workers. On the other hand, young artists’ access to lively downtowns becomes blocked when restrictions on urban construction cause living expenses to go up. What should go up instead are skyscrapers, whose efficient use of limited acreage helps reduce the cost of city life. Locals often resist high-rises, fearing overcrowding and a loss of neighborhood character, but tall buildings designed with plenty of ground-floor shops and entertainment generate a vibrant street life of their own.

In the US, many policies encourage people to leave cities for suburbia. The mortgage-interest tax deduction makes home ownership more valuable, while federal support for highway construction makes it easier to work in town and live in the suburbs. However, large suburban home sizes and long commutes increase energy costs and pollution. Meanwhile, attempts to limit construction in greener states shift housing demand to browner areas, which worsens overall environmental damage. Cities, on the other hand, reduce per-person environmental impacts with densely built neighborhoods and shorter commutes. Wooded urban parks and enhanced entertainment options remedy some of the quality-of-life issues that drive residents to the suburbs.

Every city is unique, and each succeeds in its own way. Some, like Hong Kong and Singapore, emphasize good governance and free markets; others, like Boston and Minneapolis, feature excellent universities; still others, like Paris and Dubai, offer urban pleasures. Many municipalities have become centers of finance and technology; some cities are known for the physical beauty of their locale.

Even successful cities struggle under misaligned public policies that restrict their growth while propping up dying areas. Restrictions on trade and immigration also blunt the vibrancy urban life. Meanwhile, if developing nations copy Western policies that encourage suburban sprawl, the world will face vastly increased environmental burdens.

Big cities, then, are idea factories that lead to increased productivity, improved opportunities for the poor, and reduced environmental impact. Cities are vital to the progress of human civilization; if not supported by public policy, public police should at least not constrain them.