An argument left hanging 44 years ago was joined again in earnest last week when the General Services Administration unveiled a dramatic proposal to at last complete the Federal Triangle, the vast classic revival building program that forever altered the face of the nation's capital.

The argument can be summarized by posing a simple question: To finish the grand enterprise, do you reflect the wishes of the original architects by building a park, or do you fill the remaining hole with buildings?

The GSA proposal, in the form of The Master Plan for the Federal Triangle developed by Harry Weese & Associates, follows the build option--and rightly so, although the development it proposes for the huge vacant lot on 14th Street--the proposed Great Plaza that has been the great parking lot ever since land was cleared for it some 50 years ago--is a bit too big for the site.

A bigger flaw in the plan is the form for one of the big buildings--a massive, sweeping curve facing Pennsylvania Avenue on a site that cries out for a flat background plane--is an architectural mistake. In all other respects the master plan is a gem: reasoned, thorough, and imaginative.

Edward H. Bennett, who as chairman of the Architectural Board of Consultants to the United States Treasury Department was one of the principal progenitors of the impressive ensemble of buildings that became the Triangle, once defended his creation by quoting a "Greek" proverb: "To make our city loved, we must make it lovely."

Bennett and his colleagues, each of whom designed one of the major buildings in the complex, had no doubts at all about how to accomplish this worthy and difficult end: Build more buildings in the style they liked until the job was done. Though the architectural results of their efforts were undeniably fine, it was a simple-minded approach to urban planning. But in any case they went about the task with dispatch until the economics of the Depression finally caught up with them (and thereby fortunately saved the District Building and the Old Post Office building, which they considered simply as ugly obstacles in their way).

What they had in mind as the final piece in their glorious urban puzzle--a great formal garden--has an undeniable allure, even today, that is controverted by the Weese-GSA scheme. The concept of converting an unlovely parking lot into a beautiful park has a certain angelic appeal until, given some thought, it acquires a hollow ring.

A few hundred feet south of the parking lot, which became an even more offensive eyesore in 1971 when an adjacent building on Pennsylvania Avenue was demolished, allowing the cars to wrap around the District Building in a monstrous 15-acre L-shape, is one of the finest and biggest urban park systems in the world--the Mall. Scarcely five minutes away by foot is the Ellipse. Bordering the site on the north are Pershing Park and Western Plaza, the complementary open-space centerpieces on the western edge of the new Pennsylvania Avenue.

In defining the allotment of open space and parks in the overall scheme of a city it is the rhythm of their placement that counts above all. To construct a huge new green space at this location would produce an overlong break in the well-modulated sequence of spaces in the monumental core of Washington. Clearly we are talking about a place that cries out for some kind of concentrated development, which brings us back to the questions of what kind and how much.

The Weese-GSA plan calls for two new buildings, one filling in the gap along the avenue and another on the 14th Street site across from the Commerce building. Both are big. If built they will provide nearly 1.5 million square feet of usable space, mostly for government offices (up to 1.3 million square feet, enough for 6,500 new employes in the Triangle area). Each is higher than nearby federal buildings, although the added height is cleverly disguised by setbacks starting at the cornice line of the existing structures. Space not taken up by offices is to be devoted to public uses, including a small concentration of convenience stores for office workers and a grand, floor-to-roof exhibition galleria coursing east-west through the middle of the 14th Street building. The existing parking lot, slightly reduced in capacity, will simply be dug into the ground beneath the new buildings.

Obviously, beneath a certain point, the issue of how much is too much is a matter of opinion. The reason I think this proposal is overdeveloped is that it fills up too much of the site and gives designers too little flexibility in meeting one of the main requirements of the plan. This is to break down what architect Robert J. Karn of the Weese organization called "the Chinese wall" effect of the Federal Triangle, which acts as a physical and psychological barrier between the Mall and downtown D.C.

The actual architect for the project will be chosen in a national competition, when and if the Weese-GSA plan passes review by the Fine Arts Commission and the National Capital Planning Commission and receives a $3.5 million appropriation for design from Congress. This architect (even if it were the Weese firm itself, which intends to enter) would be well served if the amount of office space were to be cut back even by as little as 25 percent. The consequent reduction in mass would allow more freedom to develop an interesting and modestly scaled relationship of buildings to open spaces on the site.

The other big fault in the Weese scheme is that glaring architectural faux pas--admirers would want to call it a daring architectural risk--represented by the sweeping curve of the building facade on Western Plaza. Admittedly, this site between two buildings so different from each other as the wedding-cake District Building and the sedate (not to say funereal) Federal Building at 13th Street, is a humdinger of a design problem, but if ever a place required a hard-edge plane instead of a "softening" curve (actually a tremendously massive facade), this is it.

Karn defends the design by saying the curve will pull visitors into the Triangle from the avenue. Reducing overall density would help to solve this problem, too.

In all other major respects the master plan, if carried out, will be a great boon. Among other important things, it proposes to complete the ragged edges of Federal Triangle buildings left unfinished for nearly half a century; to make a restaurant arcade out of what is now a parking lot in an unfinished court of the Internal Revenue Service building, a use that will superbly complement the small retail complex inside the Old Post Office Building; to restore the wonderful architectural and artistic ornaments of the original buildings; to narrow 12th and 10th Streets and line them with trees in order to lure tourists northward from the Mall; and, perhaps most important of all, the plan asks that the whole Triangle, so filled with hidden places of interest, be opened to people--bureaucrats, tourists and residents alike.

This was part of the original intention when Bennett and his Beaux Arts boys first got together back in the 1920s. To make it come true now would be a tremendous, restorative gift.