At the heart of the nation's first museum devoted to the history of Arab-Americans is a mosaic-decorated courtyard surrounding a small fountain, evoking the traditional courtyard of Arab lands. A symbol of hospitality, it is also, typically, a feature of one's home, and this museum is, in its way, a declaration that Arab-Americans really are at home, not just in Dearborn (where some 30 percent of the 100,000 residents identify themselves as Arab-Americans) but in the United States itself.

The surest sign of that may be that, like other groups, they have built this museum honoring their past and their identity. And the 38,500-square-foot, $16 million Arab American National Museum, which opened in May, is, like other museums of American hyphenation, at once an assertion of difference and of belonging, a declaration of distinction and of loyalty. It would be making a political statement even if it weren't directly across the street from City Hall.

The museum was also designed to reflect the interests of its constituency: Arab-Americans. That is a source of its strengths, and suggestive too of its weaknesses: it eagerly wants to celebrate that identity and create a strong political front; it is less interested in reflecting on difficulties and making distinctions. Before the museum was begun, a group of planners, including a sociologist, Anan Ameri, who became its director, spent six months traveling to Arab-American communities, soliciting ideas.

''The museum was built to tell our story,'' Dr. Ameri explained before leading a critic on a tour. ''But before we can tell our story, we have to know what the Arab-American story is.''

''People don't know'' was a recurring refrain in these consultations, Dr. Ameri said. ''People don't know'' about who we are, went the complaint. So the museum includes a handsome library and an exhibit chronicling the arrival of Arabs on American shores, including such unusual figures as Hadj Ali, a 19th-century Syrian immigrant recruited by the United States to train camels for the Western deserts.

''People don't know'' about Arab contributions to civilization, continued the refrain, so surrounding the central courtyard are display cases summarizing achievements of early Arab civilization; or about everyday life, so another exhibit shows how typically American Arab-Americans have become; or about their accomplishments, so another display shows Arab-Americans in politics (John Sununu), political activism (Ralph Nader), literature (Kahlil Gibran), journalism (Helen Thomas), movies (William Peter Blatty) and opera (Rosalind Elias).

Four Arab-Americans claimed to have invented the ice cream cone. One Arab-American has worked with every presidential administration for 50 years -- as the White House Santa.

In all of this, though, the museum, designed by the Cincinnati-based Jack Rouse Associates, hews too closely to its immigrant-museum genre; it seems overly familiar, with only the names and stories varying from group to group.

But this eagerness to construct an overarching Arab-American identity can also be a virtue. It is difficult to imagine a similar museum in Europe, where the hyphenated identities of Arab immigrants are far more troubled. John Zogby, the Arab-American pollster, has argued that one reason for this difference is that it is so much easier to join the mainstream in the United States.

The museum seems to reflect that in its efforts at conciliation and unification. Constructing Arab-American identity means accommodating differences both within the community and with its adopted society. Even on so raw a subject for Arab loyalties as Israel, unusual moderation is evident. Though Palestine is named one of 22 Arab countries on an ''Arab World Map'' (and is given the boundaries of the West Bank and the Gaza Strip), the museum's commentary refers to this Palestinian ''state'' with objective propriety: ''The lack of political resolution to the Israeli-Palestinian conflict has hindered its establishment.''

But there are also problems with the museum's unifying impulse. The commentary on each Arab country, for example, is little more than a travelogue without any discussion of profound problems, at least some of which inspired these Arab immigrations.

Perhaps there was a reluctance to cause offense, because, as the exhibits point out, Arab-Americans have traditionally identified themselves with their village or country of origin rather than with a pan-Arab sensibility. At least three of those nations also helped construct the museum. Qatar contributed $1 million, Saudi Arabia and Dubai $500,000 each.

There are other differences among Arab-Americans that might have been explored. The 2000 United States census counted 1.2 million Americans who identified themselves as Arab-American; a Zogby poll that same year suggested the true number was closer to 3.5 million; the museum cites a later Zogby statistic of 4.2 million. This variation may also suggest the ambiguities of identity. The Zogby poll in 2000 pointed out that 66 percent of Arab-Americans identified themselves as Christian, 24 percent as Muslim. What are the cultural and political differences, then, between recent Muslim immigrations and older Christian waves of immigration, which were largely from Lebanon and Syria? Many disparate communities are embraced in this single label, just as with other hyphenated American identities, like Hispanic or Latino. But the museum's impulse is to incorporate, not to dissect. An effort is even made to be historically accommodating. One label points out that in discussing art, the term Arab-Islamic ''does not necessarily refer to art based on religion, but rather based on culture.'' Judaism too is given a place: ''There have been significant populations of Arab Jews in Iraq, Yemen, Syria, Egypt and Morocco,'' the museum notes. That ancient world (which until the 1940's included more than 900,000 Jews) is represented by a photograph of a Tunisian synagogue -- the same one, the exhibit fails to mention, that was bombed by Al Qaeda operatives in 2002. The exhibit also does not mention that perhaps 200,000 of those Arab Jews now live in the United States, creating yet another cultural variation.

Perhaps, as the museum evolves, such distinctions might be more thoroughly explored and other more sensitive issues might be more forthrightly taken on, particularly Islamist terror, which may be having a profound impact on the daily life of Arab-Americans. One exhibit, for example, shows a collage of images of Arab terrorists on television, and asks why a more accurate image of Arabs is not broadcast -- one more closely resembling another collage, of smiling children and families. But the reason is not necessarily a reflection of prejudice: Islamic-motivated terror has compelled a rethinking of everything from airport design to foreign policy; smiling families have not.

Right now 9/11 is the subject of just a single panel at the museum, on which is reproduced a November 2001 letter from a United States attorney in Michigan, requesting that the recipient come in for an interview, emphasizing that while ''we have no reason to believe'' the recipient has any association with terrorist activities, some information might turn out to be helpful. The museum comments that after 9/11 ''Arab Americans were unfairly held responsible, yet not a single Arab American was found guilty of any connection to September 11th.''

But how were Arab-Americans ''unfairly held responsible'' for 9/11, except by bigots? Some unfairness undoubtedly manifested itself in the quest for information, but who held Arab-Americans responsible as a group? The second assertion is also phrased so narrowly that it misses the point: some Arab-Americans have indeed been found guilty of financing terrorism, and reasonable doubts have been raised about some others.

Here, surely, the museum would want distinctions to be made, between those holding one belief and those acting on another. But that is something the museum should be doing throughout. Once it can feel secure in its home, it might consider making distinctions as well as showing continuities, describing in all its variety a group that is beginning to celebrate itself and its possibilities, exploring the complications of a hyphenated existence.

Photos: An Arab World Map, above, at the new Arab American National Museum in Dearborn, Mich. Below, exterior and interior features. (Photo by Above, Bill Pugliano/Getty Images; below, second from right, Edward Rothstein/The New York Times; all others, Fabrizio Costantini for The New York Times)(pg. E1); Viewing an exhibit about the American-born Queen Noor of Jordan, the former Lisa Halaby, at the Arab American National Museum. (Photo by Jeff Kowalsky/European Pressphoto Agency)(pg. E7)