BECAUSE SHE INSISTS on looking ahead resolutely -- rather than dwelling painfully on the fiery devastation of the Filene Center 10 days ago--Catherine Filene Shouse already has inspired the best in so many people around the country who share her determination to see Wolf Trap come alive again. But even as the first giant wave of generosity is rolling in, the spirit will need sustaining well beyond it if the tremendous costs of this revival are to be met.

While the estimates are by no means "hard numbers," they are staggering: construction costs today are running roughly three times what they were 11 years ago, when the cedar and steel first rose in Wolf Trap Farm Park. In addition to the 117 acres given to the government by Mrs. Shouse, there was her gift of $2.8 million as well as another $2 million in federal funds. Add to this all the special equipment added to the center and also ruined in the fire, and experts from the Park Service come up with a preliminary estimate of more than $17 million to reconstruct.

This total could decrease when the experts take a closer look at the structural damage. But even so, the distress flag stays up--the Wolf Trap Foundation has millions to go before the fund-raising appeal can be deemed a success. Individual donations--from the countless residents and tourists who have enjoyed the popular, free-to-modest-priced activities to those who have attended the higher-priced spreads of entertainment--are important to the drive. So, too, is the help offered by large national corporations, local businesses, labor and other groups.

We can't begin to list those who have responded quickly with offerings large and small, but some examples of group efforts may inspire others. There is a $50,000 contribution from RKO-General; $10,000 from the members of Local 22 of the International Alliance of Theatrical Stage Employees (of which Mrs. Shouse has been an honorary member for years); an offer from Neiman-Marcus of 20 percent of net sales in its Washington store this Thursday, Friday and Saturday; an offer from The Summer Opera Theatre Company of the total ticket sales for its gala opening night performance of "Madame Butterfly"; and scores of other pledges from merchants, performers, unions, broadcasters and people who care.

In addition to rebuilding the Filene Center, money will be needed for a makeshift accommodation of this summer's scheduled program at Wolf Trap--which Mrs. Shouse, the Park Service and everybody else involved want so desperately to go on as much as possible. That is why the mail must keep on going through, to the Wolf Trap Foundation at that special ZIP--c/o The Postmaster General, Washington, D.C. 20260.