Whatever one may think of the curious atmosphere -- half street carnival, half-inquisition--that now surrounds the El Salvador certification process, no doubt the exercise itself serves one constructive purpose: it compels us to reexamine semiannually what we are doing, or trying to do, in that country, and to ask ourselves whether there might not be another, better way.

One such effort was a column by Stephen S. Rosenfeld ("Slugging It Out in El Salvador," op-ed, Jan. 28). In it, he proposed a "diplomatic initiative" under which "there would be a cease-fire and the two sides would be left to work out their own political future." The Salvadoran government "would lose the support (for its electoral plan) it now gets from the United States . . . in return, it would gain a cease-fire." The opposition, he added, "would lose the edge that accrues to it by its military pressure, but would get an earned or agreed place in the political sun."

In that presumably happy eventuality, "the two sides would be left to work out their own political future," which--he candidly adds--"would no doubt be ragged and irregular." But, he concluded, it is incumbent upon the Reagan administration to exhaust the "diplomatic means" available to ensure that in El Salvador, "one way or another, the popular will is finally honored."

Diplomatic solutions come in all sizes and shapes. If what Rosenfeld is proposing is something other than a disguised withdrawal--and I think it is--then it must satisfy two fundamental questions: 1) what is our middle-and long- term purpose? And 2) what are the possibilities of achieving it by the means proposed?

If what we wish to do is to honor the "popular will," we might begin by noting that in El Salvador, at any rate, that has already been provisionally accomplished-- through free elections. It is a remarkable tribute to the force of cultural stereotypes (as well as some pretty unscrupulous propaganda) that many Americans simply find it impossible to credit any electoral result in Latin America that does not result in a resounding triumph for the "revolutionaries."

True, in El Salvador the left chose not to participate, but even by the most generous estimates this would have removed only 15 percent of the national community from the deliberations. Doubtless the results themselves do not point in a single, unambiguous direction for public policy in that country-- but why should they? The real issue is why so small a proportion of abstaining voters should be regarded as virtually an entire disenfranchised nation, much like the blacks in South Africa.

Second, the violent left in El Salvador is by its own admission fighting not for "a place in the political sun"--so many jobs in the ministry of education, so many changes in the land-reform bill--but for a whole new political order informed by Marxist values. If we are speaking of a political settlement in the extreme short run, no doubt the rebels will be happy enough to sit down and discuss a formula for power-sharing with the parties of the Salvadoran center and right.

But after a century pockmarked by the failure of "coalition governments"--whether in St. Petersburg, Prague or elsewhere--we have no right to pretend ignorance of what this will mean in practice. Granted, some of our European allies and the Mexicans profess to find this eventuality quite acceptable, but there is no particular reason why Americans, particularly those of a liberal temperament, should make the cynicism of other nations their own.

Third and finally, while there is no doubt that the United States could shut off military aid and thus compel the Salvadoran government to observe a cease-fire, as some suggest, who would compel the other side to keep its part of the bargain? To pin that hope, as Rosenfeld does, on our "Latin American diplomatic friends" glosses over the inconvenient fact that these same allies looked the other way when their painfully fashioned accord in Nicaragua--which included nonalignment and free elections--was precipitately overturned by the Sandinistas.

Nor is it reasonable to expect much in this regard from the government of Nicaragua. Those who imagine that this is the fault of the Reagan administration need to be brought up sharply by the facts: the Sandinistas had already fixed their present international role when President Carter finally felt compelled to shut off aid. There may yet be some value --obscure and not yet established--to one more approach to Managua. (For all we know, it may already have been made.) But by now it should be clear that pragmatism and good sense are not the overarching values of the government there.

Insofar as Central America as a whole is concerned, it is one thing to object to a policy because it is unpleasant and difficult, another because it is wrong. Throughout the debate over El Salvador, this distinction seems to have been lost. Is the present course really so bad that it justifies leaping into a void of good intentions and diplomatic spit-and-baling-wire?

We are speaking here not to those critics who believe that Marxist governments are not merely the wave of the future in Central America, but much preferable to any other. With such people there can be no argument; they are simply wrong. But the rest of us deserve better --by the dictates of realism and of our own values. And so do the people of El Salvador.