From the beginning I heard the refrain: different, different, different, different.

Assigned last winter to report on the National Museum of the American Indian, which will open its new home on the Mall this Tuesday, I was immediately informed by NMAI officials that it would be different from other museums, including its Smithsonian neighbors. It would be different because it would be infused with a Native American sensibility, inside and out. It would be different because it would concentrate on living people and cultures, not the dead past. Most of all, it would be different because Indians themselves -- not some non-native cultural authority -- would be in charge of the stories it told.

Even the food would be different. Want McDonald's rather than authentic native cuisine? You'll have to head next door to the National Air and Space Museum.

Maybe it was that fleeting mention of Air and Space, where I'd done some reporting as well, but one day I found myself thinking: Never mind the differences. What is it that those side-by-side Smithsonian museums have in common?

The answer is a lot more important than buffalo burgers and Big Macs. And it goes to the heart of the question of what we want our museums to be.

At first, any comparison may seem far-fetched. Walk through Air and Space and you'll find yourself craning your neck to ogle the incredible flying machines engineered by Technological Man: the Spirit of St. Louis, the Skylab orbital workshop, an array of sleekly lethal ICBMs. Stroll a couple of hundred yards down the Mall and you'll be admiring such close-to-the-Earth artifacts as a wall of pre-Columbian figurines and a pair of lovingly beaded sneakers, not to mention innumerable displays that feature living, thriving Native Americans. (The main message of the new museum can be summed up in three words: We're still here.)

But the crucial connection between the Indian Museum and Air and Space isn't visible on the museums' floors. It lies in the fact that each is beholden to a particular set of influential "stakeholders" whose worldview frames its presentations. Each museum, as a result -- despite the Smithsonian's historic commitment to the straightforward "increase and diffusion of knowledge" -- is open to the charge that the knowledge it is diffusing may be skewed.

The Indian Museum is acutely conscious of this potential criticism. Founding director W. Richard West Jr. has said repeatedly that his institution has "complete respect" for the anthropological, archaeological and historical approaches to the study of native peoples that he and his stakeholders are rejecting. NMAI, he says, is simply adding to these approaches "the voices of native peoples themselves." In an introduction to its permanent historical exhibition, the museum specifically acknowledges that "like all other makers of history, it has a point of view, an agenda." In this case, it is to let previously unheard voices be heard.

Air and Space has a different kind of stakeholder problem. The fact that it has stakeholders isn't a particular source of controversy, though perhaps it should be. The museum got badly burned, a decade ago, when it took on an explosive topic that drew stakeholder fire.

The National Air Museum was created by Congress in 1946 to, among other things, "memorialize the national development of aviation." Its godfather was Gen. Henry H. "Hap" Arnold, who'd commanded the U.S. Army Air Forces in World War II. Thirty years later -- with the exploration of space added to its name and portfolio -- it opened what amounted to a grand showcase for NASA, the military services and the aerospace industry on the National Mall.

Not long after this, however, curators at other Smithsonian museums began presenting exhibits that raised historical questions rather than just celebrating historic accomplishments. Air and Space was behind the curve but, by the early 1990s, it was trying hard to catch up. To that end, it decided to develop a question-raising exhibition of its own.

One version of what happened next runs as follows:

A bunch of "revisionist" Smithsonian curators planned to exhibit the Enola Gay -- the famous B-29 that dropped the first atomic bomb on Hiroshima -- as part of a show that questioned, among other things, the necessity of dropping the bomb in the first place. Alerted by a veterans' group called the Air Force Association, an outraged press and public rose up and caused the exhibition to be canceled. And why not? As some members of Congress put it in a letter to Smithsonian management, the bombing was "one of the most morally unambiguous events of the 20th century."

An alternate version goes like this:

Among the stakeholders of Air and Space, the U.S. Air Force and the aerospace industry reigned supreme. Having obtained a draft script from the museum, the Air Force Association -- a powerful lobbying group that, while technically independent of the Air Force itself, clearly represents military and industry interests -- went public with a preemptive strike on the exhibition. The politically naive Smithsonian got its clock cleaned. When the Enola Gay finally went on display, visitors were not asked to consider either the necessity or the consequences of the Hiroshima bombing. But they did get to see a neat plane.

Whichever version you choose, the power of the stakeholders is clear.

Robert McC. Adams was the Smithsonian secretary most responsible for the Indian Museum's creation and was still in office when the furor at Air and Space broke out. When I suggested to him recently that the level of stakeholder influence on the two museums was equally high, Adams laughed. Then he said, "I hope you make that point."

The former secretary went on to point out that the question of stakeholder influence is hardly confined to two museums. The Smithsonian, he said, has "very complex relationships with all kinds of constituencies, including the American public," to which it must be responsive. This is a subject of "continuing contention" -- whether you're talking about a wealthy donor's desire to sponsor a particular kind of historical exhibition or the public's devotion to displays of first ladies' gowns -- because it often conflicts with what the institution sees as its scholarly and educational mission.

Yet the stakeholders question is scarcely a black and white one. Without them, Adams said, the Smithsonian couldn't pursue its mission at all.

What's more, some stakeholders really are different from others. And this is where the experiences of Air and Space and the Indian Museum diverge.

Air and Space has what you might call mainstream stakeholders. The historical narrative preferred by the Air Force, NASA and the aerospace industry fits comfortably with the way the majority of Americans like to think of themselves: as innovative, ingenious people prone to pushing technical envelopes and expanding frontiers, as lovers of peace who employ their military might exclusively in just causes.

Precisely because their worldview is widely shared, the stakeholders' influence on Air and Space goes largely unremarked, except when something like the Enola Gay comes along. But while the museum's curators have done much excellent work, they're not likely to revisit the question of strategic bombing any time soon. And it's worth noting that Air and Space has never done a significant exhibition on Vietnam.

The Indian Museum's stakeholders, by contrast, could hardly be more visible, and their views could scarcely be called mainstream.

"It's a very different situation when your stakeholders are members of a racial and cultural minority with a very disturbing history and a set of grievances against the United States, rather than being entwined with U.S. aspirations," says University of Illinois historian and former NMAI board member Frederick Hoxie. For such a minority to control a museum in the shadow of the Capitol dome -- well, it will be interesting to see how this story plays out.

How should it play out? What do we want our museums to be?

In an ideal world, perhaps, we could look to both Air and Space and the Indian Museum as forums for competing views of the past and present, safe spaces for the contemplation of complex realities that touch us all. In the world as it exists, however, the best we can expect may be that they make their biases clear.

The introductory video in the Indian Museum's historical exhibition ends on a cautionary note. "Here we have done as others have done: turned events into history," the narrator says. "So view what's offered with respect, but also skepticism. Explore this gallery. Encounter it. Reflect on it. Argue with it."

It's a message all museum-goers might do well to keep in mind.

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Bob Thompson, a Style reporter, has written about Smithsonian museums for The Post's Sunday magazine and for Style.