The nation’s capital is the only American metropolis where debates still break out periodically between architectural traditionalists and architectural modernists. Why does this debate — once dubbed “battle of the styles” — persist in Washington? Why is modern design in this city still a hard sell at times?

Today almost all practicing architects in the United States are, in the broadest sense, modernists. Just ask the thousands of architects in town this week attending the 2012 American Institute of Architects national convention. Their talents and aesthetic tastes vary widely, but few design buildings replicating architecture of the past or buildings festooned with historic motifs and ornamentation borrowed from previous centuries.

The latest debate in Washington concerns Frank Gehry’s controversial, non-traditional design for the Eisenhower Memorial. The design has attracted much criticism from many quarters, and for many different reasons. But it has been especially condemned by those who assert that classicism is the only appropriate design language for creating a national memorial or monument in Washington.

In fact, some classicism advocates do not limit their critique to memorials or monuments. Dismissing much modern architecture, they believe that new buildings, particularly in Washington, should be clones or derivations of Greek, Roman and Renaissance antecedents.

Members of the Washington-based National Civic Art Society are among the most outspoken critics of the proposed memorial, and of modernism in general. The society is “dedicated to the traditional, humanistic practice of architecture, urban design and the fine arts, advocating the humanist tradition as the unrivaled source of artistic forms and conventions.”

The “humanist tradition” cited by the society refers to the classicism of antiquity rediscovered and reinterpreted by Renaissance, post-Renaissance and Beaux Arts architects and scholars. Humanism was the rational antidote to anti-humanistic deism and mysticism of the Middle Ages and Gothicism.

But the society’s exclusivist credo tolerates no deviation, asserting that humanist tradition is “unrivaled.” Clearly, “unrivaled” means that non-traditional concepts for creating art and architecture are inferior and must be rejected.

Classicists predicate their argument on notions of familiarity, tradition, nostalgia and meaning. Universally recognized classical motifs and ornament have been around for more than 2,000 years. People presumably associate classicism with stability, permanence, authority, elegance and grandeur. National Civic Art Society members believe that modern architecture is devoid of these attributes.

Thus, the society argues that Washington has been and should continue to be a city of classically inspired architecture. They support their argument by pointing to countless classically styled government and civic edifices such as the U.S. Capitol and White House; the Supreme Court; Union Station; the National Gallery of Art West Building; the Lincoln and Jefferson memorials; and the Federal Triangle. All were built in the 19th and early 20th centuries, as were thousands of traditionally ornamented residential and commercial buildings.

But these arguments are fallacious.

Classicism in America was an 18th- and 19th-century European import, embraced here because, before and after independence from Britain, Americans admired and emulated European culture and architecture. After all, colonial America lacked indigenous architectural traditions. Does this reasoning still hold?

Greek and Roman classical form and ornament evolved as manifestations of how buildings were constructed, a reflection of limited structural options, building materials and standardized decoration. This design language endured because, until the 19th-century Industrial Revolution, construction technology remained relatively unchanged.

In the 20th century, architecture underwent dramatic transformation. Innovative materials, machines and construction methods appeared. Unprecedented functional needs and building types emerged. New technologies and building systems were devised, enabling architects and engineers to address new physical, environmental, social and economic challenges unknown in past centuries. This is why so-called modernism encompasses so many styles, and why formulaic, one-size-fits-all classicism makes little sense and has less meaning today.

Most Americans, including architects, appreciate historic architecture and are committed to its preservation. But I doubt that many want or expect 21st-century architecture to look like it was transplanted from the past.

AIA convention-goers probably won’t be aware of any strident discourse about traditional versus modern design. What they will be aware of is Washington’s increasingly diverse styles of architecture, including very modern works, perhaps unexpected in a city known for its conservative aesthetic tendencies.

And they will see courtyards, colonnades and layered facades; buildings with columns, beams, arches, domes and vaults; and architecture visually exploiting symmetry, asymmetry, axiality, transparency, rhythm and repetition. This will remind them that timeless elements of geometric composition are classic, not classical. Independent of style, these elements never go out of fashion.

Roger K. Lewis is a practicing architect and a professor emeritus of architecture at the University of Maryland.