AFTER NEARLY 30 years of living with affirmative action, our society has resumed the debate about whether this method of remedying entrenched patterns of discrimination is a good idea.

I believe it is.Such patterns still pervade the structures of our society, despite three decades of impressive achievements. I also believe that revisiting the moral and legal ground out of which the concept sprouted and grew affords the opportunity to clarify what affirmative action is and is not.

In the current debate, as in the past, one still hears echoes of the black-white polarity that is the indelible signature of U.S. social history. Nonetheless, affirmative action raised our consciousness about discrimination in general, regarding not only blacks but women, sexual minorities and disabled people.

White workers and others have called affirmative action a mandate for reverse discrimination that requires employers to pass over better qualified white people who bear no responsibility for past discrimination. But is it really?

It simply doesn't hold water that restructuring a discriminatory status quo to create a system of nondiscrimination constitutes reverse discrimination.

What can be said is that the restructuring probably feels like reverse discrimination because something has been lost: White males have lost the favoritism they so long enjoyed as members of the highest caste in a system that distributed jobs on the basis of race and sex. But the favoritism was not fair in the first place.

Another criticism of affirmative action is that it ignores individual merit in pursuit of the desired proportion of people of color or women. Merit, the critics say, should be the sole basis for whether a person gets a job or is admitted to a school.

Well, indeed it should. But what societal model do the critics have in mind?

Not the United States, which was never a meritocracy. Our history and traditions are those of a structurally discriminatory, caste society in which determinations of merit have been color-coded and gender-referenced. Affirmative action didn't come along to taint a process that never existed.

Despite progress, racial exclusion and impediments to exercising the rights of citizenship are still pervasive. In many locales, blacks are still effectively denied full participation in the political process.

In many school systems, North and South, black and Hispanic children are disproportionately suspended, unjustly channeled into low-ability tracks and given inferior and inadequate education at a time when, to an unprecedented degree, higher education is a crucial prerequisite to economic opportunity.

In truth, the strongest advocates of ending affirmative action today are people who never supported it in the first place. Their urgings should not be heeded. Now is not the time to relax pressures that have only just begun to break the habits of discrimination. The need for affirmative action, carefully crafted and fairly administered, is still critical.