IN the year since his election, as he has since he first appeared on the national stage, Barack Obama has embodied the fundamental paradoxes of race in America: that we live in a still racially fragmented society; that we share a public culture with an outsized black presence, but that in the privacy of homes and neighborhoods we are more segregated than in the Jim Crow era; that we worship more fervently than any other advanced nation, in churches and synagogues that define our separate ethnic identities and differences, to gods proclaiming the unity of mankind. Why are we this strange way? Is President Obama the ultimate expression of our peculiarities? Has he made a difference? Can he? Will he?

We became this way because of the peculiar tragedies and triumphs of our past. Race and racism scar all advanced nations, but America is peculiar because slavery thrived internally and race became a defining feature of personal identity.

Slavery was quintessentially an institution of exclusion: the slave first and foremost was someone who did not belong to and had no claims on the public order, nor any legitimate private existence, since both were appropriated by the slaveholder. The Act of Emancipation abolished only the first part of slavery, the master’s ownership; far from removing the concept of the ex-slave as someone who did not belong, it reinforced it. The nightmare of the Jim Crow era then extended and reinforced the public slavery of black Americans right up through the middle of the 20th century.

At the same time, the status of blacks as permanent outsiders made whiteness a treasured personal attribute in a manner inconceivable to Europeans. Whiteness had no real meaning to pre-immigration Swedes or Irishmen because they were all white. But it became meaningful the moment they landed in America, where it was eagerly embraced as a free cultural resource in assimilating to the white republic. In America race had the same significance as gender and age as defining qualities of personhood.