''Maya Lin's apt, simple, stunning conception for the Vietnam Veterans Memorial has passed the test of time,'' declares Washington Post architecture critic Benjamin Forgey {Style, Feb. 13}, who then goes on to describe two serious challenges to that design.

Nearly a majority of the members of the House of Representatives are supporting legislation to place a U.S. flag at the center of the wall. And with the backing of the secretary of interior, the Vietnam Women's Memorial project is pushing to add a statue of a nurse at the memorial.

Mr. Forgey judges the Vietnam Veterans Memorial not as a national monument, but as a work of art. The standards are not the same. We build monuments to express everlasting dedication to our civilization's highest values. "The monument," explained American social philosopher and architecture critic Lewis Mumford, "is a declaration of love and admiration to the higher purposes men hold in common."

The Vietnam Veterans Memorial embodies no such values. In fact, designer Lin purposefully did not make any statement, but left "it up to the viewer" to determine the message of the wall. While such ambiguity may make for great art, it rarely results in a great memorial.

Since it was dedicated, at least four suicides have been attempted at the wall. One was successful. It is a testament to the artistic power of the Vietnam Veterans Memorial that it can move men to take their own lives. However, that is not the kind of inspiration that we need or want in our memorials.

The addition of a flag or a statue of a nurse will affect the artistic integrity of the design. But the Mall is not an art gallery. It is a place to preserve what the people of the United States hold most dear to them. The two proposed changes are an inevitable attempt to give a voice to a memorial which so far has been silent on a deeply troubling era in our history.