It has the lofty ring of a just cause, but the proposed Vietnam Women's Memorial, which has been approved by the secretary of the interior and which will be considered today by the Commission of Fine Arts, is not a very good idea. To be precise, it's a bad one.

This is not to say that the women who served in the U.S. armed forces in Vietnam were not brave, did not perform essential duties, do not deserve our respect. It is simply to point out that if our female veterans deserve more conspicuous honor than they already have received at the Vietnam Veterans Memorial in Constitution Gardens, where the names of the eight female dead are inscribed along with those of their male counterparts, then they should be given such honor elsewhere.

To add a statue of a nurse to that extraordinary memorial -- the central feature of this misguided proposal -- would create a serious symbolic imbalance in one of the nation's preeminent commemorative places. The project raises questions of proportion, of political judgment, of precedent, of placement, of procedure.

The issue of proportion should have been obvious to Interior Secretary Donald Hodel and to all of the senators and representatives who have endorsed the idea, but, of course, it wasn't. With their hearts in an idealistic stratosphere and their minds firmly on the female half of the electorate, they took the easy way out.

This is not so much a question of numbers -- although it's true that fewer than 10,000 American women served in Vietnam during the years that nearly 3 million men did tours there -- as of symbolic integrity. There is just no way the statue of the nurse will not be perceived as a separate-but-equal counterpoint to the three bronze soldiers already at the site.

There still are people who will argue that the site now comprises two memorials -- Maya Lin's competition-winning design for the V-shaped wall of polished black granite, and the three infantrymen by sculptor Frederick Hart (now a member of the Commission of Fine Arts). And there is no gainsaying the irony that, by forcing the installation of the statue, those who attacked Lin's design as incomplete created a precedent for adding figurative elements to the memorial.

But the memorial is complete. The siting of the three soldiers and the flag standard in a shaded alcove near the wall's western tip (a decision in which the Commission of Fine Arts played a paramount role) ensured that these elements would form an appropriate entry to the long and always moving march along the wall. And Hart's realistic figures face the wall with an ambivalent tension that enlivens the space between them.

If this is not a wholly satisfying union of abstract and figurative commemorative art, neither is it dissatisfying; my strong belief continues to be that over a long period of time the relationship between these elements will become increasingly symbiotic. In any case the symbolism is clear and complete: The wall and these soldiers, the point men of an infantry squad, are intended to stand for all who served.

This definitively cannot be said of the proposed nurse -- she represents a special group. Furthermore, as designed by Minnesota sculptor Roger Brodin and sited by landscape architect Elliot Rhodeside, she would be just an isolated figure in the woods, with almost no psychological or physical relationship to the memorial as a whole.

After considering several places along the memorial's southern perimeter, Rhodeside selected a grove about as far from the wall as possible. This can be seen as becoming modesty, but it also can be interpreted as an acknowledgment that this figure really doesn't belong. "Why is this statue here?" will be a natural question -- to which a cynic might answer, "Politics as usual."

A corollary question, of course, is if we begin to single out veterans by gender, why not select them by ethnic group? Why not an American Indian soldier, an Italian American? Or, if we begin to pay tribute to specialties such as medicine, why not others: why not engineers, or Seabees, or pilots, or supply sergeants? After all, there are spots along that tree-lined ridge sufficient for an entire platoon of figurative monuments.

It was to prevent this sort of proliferation that Congress last year adopted the Commemorative Works Act, which mandates congressional approval of all memorials in the nation's symbolic center. Initially, the National Park Service wisely maintained that such approval would be required for the Vietnam Women's Memorial, but the boss, Hodel, disagreed. Consequently, according to the original law providing for the Vietnam Veterans Memorial, this proposal now needs but approval by the Commission of Fine Arts and the National Capital Planning Commission.

It should be clear, however, that it's time to leave well enough alone. In this case, well enough is exceptional.