The papers are full of news about internal transformations being undertaken in Russia and China. Their situations are differentand competitive but leave the sense thatthe communist system, far from being the prisoner of dogma and historical inertia, is showing an unexpected capacity for nonviolent renewal -- supposedly a unique democratic property.

We shall see over the next few years, or decades, how much substance there is to this prospect. But meanwhile the very anticipation of change on the communist side of the ideological divide becomes a political factor on the democratic side. We are embarked on a long inquiry into whether and how we can best live with communist societies whose progress is no longer centered in the military sphere.

What gives this inquiry its distinctive tang is that, as we have seen with Beijing for more than a decade and are seeing with the Kremlin now, rigid failing communist states link their modernization and renewal to a general opening up to the Western world. They want trade and technology, a respite from the economic and political skewing that goes with heavy external confrontation and, not least, a bonus of privilege (foreign travel, movies) for their middle class.

This is how we come up to what many people feel is a historic opportunity to put relations with the communist world on a new basis: the combination of stirring within communist societies and, simultaneously, their reaching out.

One foundation for this hope is that things have already gone far and well with China, which, as a distant and less menacing case, was a good place to start. Nearly all of our political spectrum and, it appears, much of theirs have accepted the uses of close Sino-American ties. The connection has gone far enough to make it possible for the occasional disagreement -- China's sale of Silkworm missiles to Iran -- to be aired in public and to have its fallout contained.

As it goes with China, so now may it go with Russia? It is a dizzying prospect that has already begun to disorient American politics, turning liberals into a Ronald Reagan cheering squad on arms control, for instance, while leaving a big part of his old conservative constituency muttering and climbing the wall.

Anyone with half a sense of history will hesitate to salute the arrival of a new era. But someone with the other half will keep the door ajar and ask, along with a provocative Yugoslav observer named Bojan Cvijetic, whether a new era may not now be struggling to be born.

Washington, Cvijetic writes in Belgrade's Review of International Affairs, continues to insist that only American strength, including the Reagan Strategic Defense Initiative, brought Moscow to dialogue. On its part, Moscow tends to hold that its peaceful initiatives isolated the Reagan administration in domestic and international opinion and compelled it to moderate its ways. (That Gorbachev will practice more of this sort of political jujitsu on Reagan is precisely the American right's summit fear.)

Still, the Yugoslav writer is encouraged by 1) the promise of arms control, 2) the fencing off of arms control from regional disputes (what Americans would call delinking), 3) the ongoing consultations on those disputes (yes, at the same time, linking) and 4) certain signs of appreciation for aspects of each other's system.

To me, that last item counts heavily. I see little to admire in the existing Soviet system, though one doesn't have to be gratuitously abusive about it. But there is a kind of Soviet appreciation for the American system that matters considerably -- the kind reflected in Gorbachev's experimentation with glasnost and market ways. The more of it that Americans see, the more appreciation they will have for the Soviet system -- and the more interest they will have in putting relations on a firmer basis.

This has little to do with Reagan, who, in his sunset days in the White House, is moving toward a policy that American politics can likely sustain. But would the Politburo carry forward Gorbachev's commitment to improving relations if he faded or fell? In China this week, Deng Xiaoping appeared to be passing on a decade's progress to like-minded successors, but in the Soviet Union the country's new course rests on the uncertain fortunes of one man.