INDEPENDENCE Day, the Fourth of July, is an occasion this year for Americans to reflect on how their Supreme Court may change with the departure of Associate Justice Thurgood Marshall.It was a foregone conclusion that President Bush's nominee to replace him would be a conservative. The question was how conservative a nominee would the White House try to get past the Democratic-controlled Senate, which must approve all high court appointments. The fight over the nomination of Robert Bork to the Supreme Court in 1987, which the Reagan White House ultimately lost, showed that the Senate cannot always be counted on to give the president his nominee. The American polity is suspended between two poles: the Republicans, the party that keeps winning the White House; and the Democrats, the party that keeps winning the Congress. Neither branch alone can claim that it expresses the popular will. But inevitably, the post-Marshall court will be different. As his parting shot, Marshall listed 17 "endangered precedents" at whose margins the high court has been chipping away. For those "in the mainstream" of society, this may not matter very much, but for those already on the margins themselves of American society, it will matter a great deal. Over the past several years, senators examining presidential nominees to the Supreme Court have wanted to be sure they respected the principle of stare decisis, of letting decisions stand; today's high court seems to be quite eager to overturn certain precedents. And now we hear talk of a "rollback" of rights, which seems ahistorical, if not downright absurd. An occasional correction, an adjustment to an earlier ruling that has clearly proven unworkable, perhaps. But to roll back a right is like reversing the flow of a river, or "undiscovering" a scientific principle. This is not to say that there aren't real grounds for concern about the kind of country the United States will be without some liberal voices on its high court to balance the conservatives. And it should be noted that it is the authoritarian, or to put it more benignly, traditionalist strain of conservatism, rather than the libertarian, that has been coming to the fore of late. Thurgood Marshall is, of course, the only black ever to have sat on the Supreme Court. It is a triumph of the American ideal that the great-grandson of a slave, of a man who literally didn't count as a full human being according to the Constitution as it stood then (see article 1, section 2) could do so much to change people's lives. Marshall is also the only member of the court to have defended anyone against a charge of murder. He knows in his bones that the civil-liberties protections inherent in the Bill of Rights are not just technicalities that might keep the police from doing their job. They are important legal principles that people he knows might need to invoke. It is sad that Marshall has departed, sadder still that he has gone on such a note of evident frustration and despair. But the law and its interpretation cannot be so fragile as to dwell in one man. That mighty Declaration which we celebrate each year with fireworks, those splendid exclamations of democracy, asserts that it is "self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights...." It took the American people nearly two centuries to get from the Declaration of Independence to the Civil Rights Act of 1964, but the latter was surely implicit in the former from the beginning, as the blossom is in the bud. Similarly, Supreme Court decisions such as Brown v. Board of Education, the landmark school desegregation case Marshall won before being elevated to the court; the Miranda decision, which requires police to notify criminal suspects of their legal rights; the rulings on privacy rights and others need to be seen as deeply rooted in a Constitution that is more than 200 years old, and whose Bill of Rights has antecedents that go back centuries into English common law. These high court rulings were not flukes, not a single justice's whimsical interpretation or the product of a chance conjunction of elements unlikely to be repeated. The principles behind those rulings are valid as ever; they cannot be allowed to be taken from the American people.