There are two things that everyone knows about the United States -- both believed with equal firmness (and, for that matter, both equally true) though they seem to contradict one another.

One is that America is the great melting pot where people from Lithuania love and work side by side with people from Lebanon, nourish their bodies with the same processed foods, thier minds with the same television programs, send their children to the same schools, drive the same cars and complain about the same taxes.

The other is that America is a loose confederation of warring tribes, united by geographic proximity but divided by ethnic origin, religious belief, social and economic status, political ideals and cultural tradition. These tribes are engaged in a more or less constant warfare, a jockeying for power and position; the battlefields usually are the centers of government in all departments and on all levels, but sometimes the warfare breaks out in the streets and people begin to ask themselves what has happened to the American dream.

What has happened, according to the evidence presented by Paul Cowan in "The Tribes of America," is that the dream is still in process; the melting goes on -- though perhaps more slowly, because the still unmelted material is the kind that is hardest to melt. The tribal reality and the reality of Homogenization do not contradict one another any more than a butterfly contradicts a caterpillar.

Cowan's sampling of Americans for this book (and for the series of articles in The Village Voice on which it is based) is hardly a true or complete cross section of the American population, as he would readily agree. His focus is on those who are still "unmelted": long-haul truck drivers, migrant farm workers, black people on southern farms and in northern cities, illegal Mexican immigrants, Bible-belt fundamentalists, Orthodox Jews (mostly Hassidic) in New York City, coal miners in embattled Harlan County, Ky. His sampling of Middle America is also unusual: the jurors in the case of the Harrisburg Seven, a group of war resisters who were put on trial under the Nixon regime on the charge (among others) of plotting to kidnap Henry Kissinger.

Some of his subjects are unassimilated chiefly because they resist assimilation, most often for religious reasons but also because they prefer a style of living that differs from the American mainstream. Others are outside of that mainstream not through choice but because their fellow Americans are not yet ready to accept their skin color, their language problems, their poverty or their Spanish surnames.

In Cowan's writing, the traditional American dream lives most vividly in Juarez, where poor Mexicans look across the Rio Grande and think of Texas (Texas!) as a sort of promised land. It is viewed with the most unmixed horror and contempt on New York's Lower East Side, by Rabbi Joseph Singer and his faithful, who have managed to build and maintain their own traditional society here after fleeing Hitler's holocaust.

Cowan writes as a reporter, not a social analyst, sticking closely to what he actually has seen and heard for the most part and only occasionally allowing himself the luxury of editorial comment. Such comments, when they are given, are usually succinct and practical, and at their best they are another kind of reporting -- personal reporting in which Cowan shares with the reader a stage in his own learning process.

Thus, he records his surprise at discovering that, on issues not related to race, the Rev. Jesse Jackson and his congregation are often conservatives having "a great deal in common with people who seemed to be their enemies in territorial battles." This perception leads him to the book's most cogent formula for transcending most cogent formula for transcending tribal differences: "For blacks and whites alike, any progressive movement in America must combine economic radicalism, an appreciation of tribal differences, and a genuine respect for ideas about family and personal discipline that seem old-fashioned from the vantage point of Greenwich Village or Berkeley or Georgetown or Harvard Square."

In his final chapter, discussing the jurors in the Harrisburg trial, he examines his own prejudices about Middle Americans and records with a bemused delight what he learned from that trial:

"For many Americans democracy is a religion. Certain tasks -- like jury duty -- inspire them to transcend their tribal prejudices and regard themselves as guardians of a precious faith... Sometimes it is possible to unify Americans in situations that call for generosity or fairness instead of dividing them into battles over physical or psychological turf."

Here, he touches the crucial way in which America is in fact a melting pot: The ideas on which this country was founded are the bond that makes us one nation, and their goodness is generally accepted by all of us regardless of tribal differences and the distorted perceptions that derive from self-interest.

This is a small, tenuous theme in a book that is largely a chronicle of the way we abuse one another, but it is implicit throughout and it offers the best hope we have that the warring tribes of America can reach a peaceful modus vivendi .