"It is terribly important that Williamsburg be a success. If it produces anything like the bickering that followed Versailles, the psychological effect could be disastrous. It could plunge the world into a real depression."

That's the view of former West German chancellor Helmut Schmidt, as quoted by George de Menil in a short history called "Economic Summitry," just published by the Council on Foreign Relations.

One of the criteria by which Schmidt wants to judge Williamsburg is whether the summit tries "to stabilize exchange rates." In a widely quoted article in The Economist, Schmidt said that the present international monetary system "does not deserve the name," and must be replaced by a new system that "should be very much more stable than our current one, and it should be more flexible than in the past." Unfortunately, Schmidt doesn't tell us how to get from here to there.

Another former head of government, ex- president of France Valery Giscard d'Estaing, this week followed Schmidt into print with an Economist piece. It demanded a return all the way to Bretton Woods, with the major nations agreeing at Williamsburg to "aim at a progressive coagulation of the present system of exchange rates" over the next three years.

Of course (just to name the highlights), it's been 40 years, one Vietnam War, and two oil shocks since Bretton Woods. America's Asian adventure produced a global inflation, ultimately wrecking the fixed-rate system. And OPEC's destabilizing greed robbed the floating system that replaced it of much of its promise. In the wake of four decades of change, the United States is no longer the single dominating economic force in the world, and Britain has become a second-rate power.

Secretary of State George Shultz, like many others, grants that "it's desirable to have more stability (in exchange-rate relationships) than we've had. The only question is, 'How do you get it?'"

A concerted effort to turn the history pages back can ensure failure at Williamsburg, and nail a shaky summit process into its coffin. If there is one thing certain in an uncertain world, it is that a return to fixed rates is not going to be approved--or blueprinted for the future--at Williamsburg.

Among the seven current heads of government, only French President Francois Mitterrand is making an unyielding demand for a return to a Bretton Woods system. All the others recognize that present conditions don't warrant it.

There isn't even support for the lesser step of "target zones" to keep the dollar, Japanese yen, and German mark more closely linked, as suggested by former Assistant Treasury Secretary C. Fred Bergsten and former Japanese Finance Ministry official Takashi Hosomi, among others. The problem is that ideas like Bergsten's and Hosomi's--even if short of a full-blown par- value scheme Ma la Giscard and Mitterrand-- would require a coordination of national economic policies among the major powers that--as yet--is not on the horizon.

As that shrewd observer of the international financial scene, former German Central Bank president Otmar Emminger, said here the other day, the kind of intervention needed to keep the dollar and mark linked in a "target zone" would require a two- to three-point increase in German interest rates.

"No German government or central bank president could agree to that," Emminger said.

What the Williamsburg summitteers should aim at is something a lot more modest, along lines suggested by New York Federal Reserve Bank President Anthony Solomon, and endorsed by Federal Reserve Board Chairman Paul Volcker.

Solomon proposed an "understanding" among the seven summit nations calling for modest, but joint, intervention when exchange rates have moved "clearly . . . beyond levels that are consistent with the economic fundamentals and which endanger the preservation of liberal trade and payments."

As Volcker acknowledged, no one knows with certainty what the precisely correct rate may be at any time between the dollar and the yen, or the dollar and the mark. But central bankers can surely figure out when the rates quoted by speculators in the foreign-exchange markets are totally screwy.

Even this much of a limited move toward more stability does not go down easily with the free market, no-intervention purists in the Reagan administration.

But if cool heads prevail at Williamsburg, they may settle for something like Solomon's plan, which, as he notes, is flexible and reversible, and doesn't require a big pot of money to be put up in advance. If Mitterrand will settle for half a loaf, he can probably get this much at Williamsburg.