In a new, wonderful collection of essays, “From a Cause to a Style” (Princeton, 310 pages, $27.95), Nathan Glazer asks why modernism failed: “How did a socially concerned architecture come to be condemned, 50 years later, as soulless, bureaucratic and inhuman?” It is a great question, and Mr. Glazer’s analysis elegantly weaves aesthetics, political science, and intellectual history together to answer it. Mr. Glazer is one of the last lions from a remarkable generation of sociologists, including David Riesman, Robert K. Merton, and Seymour Martin Lipset, who were both great scholars and major public intellectuals. Mr. Glazer has always been a particular hero of mine because he was the great urbanist among this remarkable crew. His work, from his classic “Beyond the Melting Pot” (1963) to this newest volume, is filled with profound insights about cities.

The right tribute to an intellectual hero is to challenge his ideas, and a good starting point is to ask whether Mr. Glazer is right that modernist architecture has indeed failed. In two ways, he is absolutely right. American consumers have decided by the tens of millions to shun modernist towers and to live instead in traditional single-family homes. In 2005, there were 1.4 million single-family homes built and only 160,000 units in buildings with more than 20 units. Mr. Glazer is also correct that much public modernist architecture is something of a disaster. Modernist public housing has often failed its residents and modernist monuments are often obscure rather than moving.

But modernism is hardly a complete failure. The glass towers that fill Manhattan are not despised by their residents, and the true modernist masterpieces, like Lever House or the Seagram Building, are surely great works of human genius. On a more modest level, modernism has achieved popular success within the home, as furniture designs associated with the ideas of LeCorbusier and Mies van der Rohe, are sold by the millions by Ikea.

The successes and failures of modernism help us make sense of the style’s strengths and weaknesses. Modernism’s stark rejection of ornamentation works best when there is something else that makes the building interesting, like the vast scale of the World Trade Center or the luxurious materials of Mies’s Barcelona Pavilion or even bright color. Lack of ornamentation helps the building’s other strengths to speak. No one minds the lack of ornamentation on the Lever House because of its astonishing shape and its lustrous color, but small, inexpensive modernist homes just look dull and shoddy.

Modernism’s second strength is that it can be cheap. If office buildings all had the stylistic flourishes of Chartres, Manhattan would be even more hard to afford. The great modernists thought that their buildings were ideally positioned to provide inexpensive, attractive density from the growing urban masses.

The first reason for modernism’s failure is that America in 2007 looks nothing like inter-war Europe where modernism began. The modernist’s world was one of poor, carelessly planned cities where cheap density was a real blessing. America ended up being rich and filled with cars. With all that wealth and all that mobility, Americans moved to car-based suburbs and chose to spend a little extra for ornamentation. Who can blame them? The end result was that modernism ended up being a bad fit for postwar America.

Mr. Glazer is more interested in modernism’s failure in delivering public buildings and his analysis is trenchant. Modernism moved from being a social movement into an elite style, and part of appealing to elites is being inaccessible to the rest. Self-referential buildings that require lots of inside knowledge to get the joke are a way of separating the cognoscenti from hoi polloi. Those who cared about such things came to control the production of public buildings, and the result was overly abstract monuments and drab towers that appeal to the artistic elite and no one else.

Why didn’t this happen in the past? Perhaps because, historically, wealth and power, not aesthetic knowledge, determined what public buildings were erected. Wealth and power were often distributed among the artistically ignorant, whose tastes more accurately reflected those of the public as a whole. Royals — from Napoleon III to Prince Charles — have been blessed by a lack of artistic training that helped their aesthetic judgments better match public sensibilities. We should also never forget that the older buildings we see are those that have survived. They survived because they were far more attractive than most of the dreck that has been built through the ages.

If there is one area where Mr. Glazer and I disagree it is his view that “scale is a problem.” The resurgence of New York, London, and Chicago, and the great, growing cities of Asia remind us of how valuable scale can be. Scale is not for everyone, but great towers enable vast numbers of people to reap the economic and social benefits from physical proximity. New York’s skyscrapers are the infrastructure that enables the city’s flow of ideas. And for those buildings, modernism is an efficient, attractive style. Millions of New Yorkers happily work and live in modernist towers. New commercial buildings in the city remain mostly modernist. Why not? People are willing to pay high prices for them.

Mr. Glazer’s superb book explores an important aesthetic movement, but it is also a warning against delegating public control over construction to artistic elites. Modernism has its place in the panoply of architectural styles, and it is particularly appropriate for large buildings in megacities. It is not well designed for building public buildings or monuments that speak to most people. Public art needs to be selected for its appeal to its users, not for some ill-defined artistic merits, and Mr. Glazer has made this case well.

Mr. Glaeser is the Glimp professor of economics at Harvard University, director of the Taubman Center for State and Local Government, and a senior fellow at the Manhattan Institute.