A curious thing has happened to the abortion debate. It remains politically hot, but it is intellectually spent. Everyone seems to know both sides of the argument backward and forward. One reason for the exhaustion is that the abortion issue has been -- and will be -- decided not by the popular branches of government, Congress or the president, but by the Supreme Court, our system's concession to aristocracy. When the outcome of a struggle bears little relation to public opinion or practical politics, debate becomes increasingly autistic. With little prospect of winning converts, both sides in the abortion debate have turned to capturing words.

Terrorist. Only a few weeks ago it seemed extremely important to pro- abortionists that those who were bombing abortion clinics be called "terrorists." The ostensible reason was that using the word would trigger FBI intervention, although the Bureau of Alcohol, Tobacco and Firearms appears to have done a fairly good job of rounding up suspects. The larger aim, of course, was polemical. Everyone hates terrorists. Moreover, anti-abortionists are generally conservative; conservatives make a big point of denouncing terrorism; to find terrorists in their midst would be an acute embarrassment. Touch,e.

Yet last month, on the weekend of the 12th anniversary of Roe v. Wade, NOW activists kept overnight vigil in some abortion clinics. The idea was to deter the bombers by putting people in the buildings after closing hours. But the very definition of a terrorist is someone who is not deterred by the prospect of harming innocents. In fact, he seeks them out in order to magnify the effect of his violence. To hold a vigil at the U.S. Embassy in Beirut, for example, would be a novel, but imprudent, defense against terrorism.

Abolition. More word play, this time on the other side. Everyone would like to borrow some of the glory of the anti-slavery movement. Moreover, for the anti-abortion side it offers a delicious irony. Its opponents tend to be liberals, for whom Abolition (and its 20th-century successor, the civil rights movement) is the most hallowed of causes. How better to hoist them than by appropriating their cause and portraying them as having betrayed it? Of course, this is all sleight-of-hand. Who is to say whether banning a social behavior constitutes Abolition or Prohibition?

Pro-life and pro-choice. Word play of a high order. It makes the opponent -- against either life or choice -- a denier of at least one-third of the promises of the Declaration of Independence. At the same time, these words, like all words that mean everything and nothing, are artfully empty. Pacifists, vegetarians, gun controllers, anti-smokers, Mothers Against Drunk Drivers and the air-bag lobby can equally claim the pro-life slogan. And who is against choice? It is hard to think of a cause that is not pro-choice, from legalizing marijuana to abolishing the income tax (contributions to the government to be voluntary). Suppose you are pro-lynching. Why not call yourself pro-choice? (A fair trial or a lynching: Let the people decide.) Until, that is, you are caught and condemned for a lynching. Not wanting to hang, declare yourself then to be pro-life.

Terminating a pregnancy. When the CIA says "terminate" (with or without extreme prejudice), the euphemism is so outrageous as to be comic. "Terminate a pregnancy," on the other hand, has a medical ring that endows abortion with instant moral neutrality. Yet, one really does not have to believe that abortion is murder to know that "terminating a pregnancy" is a different moral proposition from, say, removing a hangnail.

Pre-born. A favorite of Nellie Gray, leader of the March for Life. Pre-born child is her way, her only way, I gather, of saying fetus. The technique is to make the distinction between a fetus and a child sound like one of packaging. The point is to rig the debate: If what is at stake is a child -- differently boxed, perhaps, but a child nonetheless -- the entire abortion issue is nicely foreclosed.

Scream. As in "The Silent Scream," the anti-abortion film shown Tuesday at the White House. The idea, says the film's producer, Dr. Bernard Nathanson, is to "vault over the tired, stalemated, point-counterpoint" debate -- to go beyond words -- by showing the ultrasound image of an actual abortion. "Scream" refers to a point in the film in which the fetus' mouth appears to open. Neurologists point out that a fetus at 12 weeks is no more capable of a scream than of experiencing pain. "Perhaps the use of the word scream is a little metaphorical," admits Nathanson. ''But there is no question this child is grimacing." No matter. Just words.

Things will get worse. In an exhausted debate, all that's left to do is to rework the words. One side plumbs the lexicon of slavery and Dachau; the other speaks medicalese and clothes its opponents in every variety of political intolerance. There is not the slightest recognition on either side that abortion might be at the limits of our empirical and moral knowledge. The problem starts with an awesome mystery: the transformation of two soulless cells into a living human being. That leads to an insoluble empirical question: How and exactly when does that occur? On that, in turn, hangs the moral issue: What are the claims of the entity undergoing that transformation?

How can we expect such a question to yield answers that are not tentative and indeterminate? So difficult a moral question should command humility, or at least a little old-fashioned tolerance. Instead we get each side claiming truth by linguistic fiat. This is nothing less than a sophisticated form of lying -- moral lying perhaps, but lying nonetheless. Well? "Everybody lies," says Stepan in Camus' "The Just Assassins." "What's important is to lie well."