AFFIRMATIVE ACTION was conceived as an exact approach to an inexact problem. How, in a nation dedicated to equal opportunity, were we to chip away at racial discrimination? In its evolving guises, affirmative action would be a methodical attempt to ensure that minorities had a fair shot, and over time, would enter all strata of society.

The question that always hovered, though, was “how long?”

When could race-conscious policies be abandoned? What state of affairs was going to be good enough?

The howl of pain embodied in Supreme Court Justice Clarence Thomas’s recently published biography has given the “how long” question new force.

As a young man, Justice Thomas benefited from efforts to recruit minority students at Holy Cross and Yale Law School. Today though, he seethes over the notion of being seen as one who received special favors — seethes more over the notion that any black American, henceforth, ever should get a break based on race. If Clarence Thomas ruled the world, affirmative action would be abandoned yesterday, and his own personal history sponged clean.

Yet even as Justice Thomas profitably nurses his injuries, new evidence on the “not yet” side of the debate keeps emerging.

Most dramatic have been the events in Jena, La., where white students hung nooses at a favored school gathering spot. A subsequent brawl ended in attempted murder charges against six blacks. Cries of lopsided justice were raised, and thousands marched. But dozens of copycat noose incidents, from Terra Haute, Ind., to Punta Gorda, Fla., have made clear that old notions of racial superiority still lurk.

Dull statistics shed greater light. A recent report by the Pew Charitable Trusts found that middle-class blacks are far less likely than whites to hang onto their middle-class status. The study followed more than 2,000 children, ranging from birth to age 18, and compared their median family incomes in 1968 with where they stood in 2006. Of those reared in the middle fifth of families economically (the statistical middle class), far more blacks than whites fell on the income ladder. Among blacks, 69 percent were earning less than their middle-class parents; among whites, just 32 percent moved downward.

In a restructuring U.S. economy, a college degree has grown increasingly vital to economic success. But lately, we have been building an inherited meritocracy. Well-off white students have an overwhelming edge in being admitted, especially to top-tier schools. A growing income gap and skyrocketing tuitions have placed higher education increasingly out of reach for many students of color.

In the late 1990s, two retired college presidents, Derek Bok of Harvard and William Bowen of Princeton, studied the effect of race-sensitive policies on admissions to selective schools. Their conclusions, reported in The Shape of the River, were generally opposite those proclaimed in the Clarence Thomas School of Wounded Pride.

Overall, they found, black students were not harmed by being stigmatized, or by having been thrown in (as some skeptics saw it) over their heads.

They also performed well: The more selective the college, the more likely they were to graduate and succeed in their careers. Additionally, they were highly active in civic life.

Nor did blacks displace significant numbers of whites or Asians. Eliminating race-sensitive policies, Bok and Bowen found, would have increased those groups’ numbers by less than two percentage points. In fact, they discovered that recruited athletes often displaced more qualified applicants than minority students did.

Peter Schmidt, the author of the recently published Color and Money: How Rich White Kids are Winning the War Over College Affirmative Action, asserts that 15 percent of freshmen at highly selective schools are whites who failed to meet the schools’ minimum admissions standards but who had money and connections that swayed admissions offices.

Still, Americans are uncomfortable emphasizing race. Wouldn’t it be better, many think, to focus efforts on the economically disadvantaged instead? We’d end up helping whites along with blacks, and thereby diminish resentment.

Certainly, colleges must do better at enrolling low-income students. But, as Bowen noted in a speech this year, used exclusively, such a system would cut the number of minority students at top schools from just over 13 percent to 7 percent. Ending race-sensitive admissions policies now, as blacks are seeing both opportunity and progress erode, will not get us to “long enough.”

Race issues put many Americans at war with themselves. Whites want to be tolerant but also to side with their own. Blacks want to succeed on merit but know they will not always be seen as equal.

With every Jena, slavery’s original wound is reopened. The dilemmas seem deeply personal, and impossible to resolve. The only thing that helps is counter-examples, and lots of them. That is why, at the policy level, we have to keep playing the averages for a while longer.

M.J. Andersen is a member of The Journal’s editorial board.