Rhetoric has rarely had so strange an encounter with reality as in last week's detention of two Soviet peace activists. As the Kremlin officially welcomed the first group of international peace marchers permitted to hold demonstrations in Russian cities, the two activists were given 15 days in jail to keep them from making contact with the visitors.

The two Soviet activists, held on a charge of hooliganism, are members of a self-styled Committee for Peace and East-West Understanding. The other nine members of the recently formed committee were placed under police surveillance or ordered to be out of town by Wednesday, when the 300 international marchers, mostly Scandinavian women, are due to arrive in Moscow.

On the surface, it may seem to be simply another case of Soviet hypocrisy in encouraging antiwar activism in the West while suppressing it at home. But there is a bit more to it than that.

Apart from the characteristic Soviet aversion to anything spontaneous, the incongruous situation reflects a Russian ambiguity toward peace and war. Even the Russian word for peace--mir--injects ambiguity, for it is the same as the word for "the world." Thus, slogans proclaiming the struggle for mir can yield tricky double meanings.

Still, it is one firm factor of Soviet life that the people share a genuine fear of another war. The ravages of World War II are so deeply ingrained in the collective memory as to almost preclude popular warlike sentiments. Peace, as one Soviet analyst put it privately, is not only the mainstay of Kremlin propaganda but also reflects the deepest aspiration of the Soviet people.

At the same time, the Russians turn quickly hostile in the face of foreign threats. This is an equally genuine impulse and is cultivated by the authorities to maintain the nation's war readiness. An average man is given to boasting that if attacked his country can land a "crushing blow" on the United States or anyone else threatening it.

The appearance last year of peace movements in the West and the massive publicity which the Soviet media continue to give to antiwar demonstrations around the world predictably led here to attempts to follow their example. The formation of an unofficial peace committee only revealed the curious inconsistency of Moscow's position.

On the one hand, the Kremlin has welcomed and encouraged Western pacifism as a way to pressure Western governments to curtail military spending and particularly to block the deployment of new American nuclear missiles in Western Europe.

On the other, the authorities have intensified pressures to prevent a younger Soviet generation from dabbling in pacifism.

The official explanation is that the Soviet Union already has a peace movement with more than 80 million members, that the movement is actively promoting peace and that some years ago it managed to collect 180 million signatures for a petition against the arms race.

But while Moscow welcomes pacifism in the West, its emergence here was not to be tolerated. Senior military commanders have publicly warned against pacifist tendencies and resistance to military service.

Such perceptions are reinforced through daily media commentaries attacking a trend among Soviet youths to imitate Western styles of all kinds and ridiculing an increasingly cynical younger generation. These commentaries seek to define a national mood in which a genuine yearning for peace faces a threatening encirclement engineered by a hostile America.

In this context, any spontaneous demonstrations are seen as possibly leading to the spread of pacifist tendencies among Soviet youth. When seven foreign antiwar activists unfurled a large banner in Red Square several months ago, they were quickly bundled off by security agents. The banner read "Bread, Life and Disarmament."

The minuscule peace committee has been repeatedly warned to end its activities. Its members have been harassed. Although they have not criticized Soviet foreign policy, the activists have been accused of a deliberate provocation: rendering assistance to anti-Soviet propaganda.

The authorities have been more comfortable with organized meetings against nuclear war such as the religious conference recently attended by evangelist Billy Graham.

The peace march of Nordic women, who paraded through Leningrad with about 100 members of the official Soviet peace committee yesterday, was approved by Moscow apparently to deflect Western criticism that the Russians were afraid to allow Western antiwar activists to hold peace rallies on Soviet soil.

The participants are from Norway, Sweden, Denmark and Finland and many of them had taken part in last summer's antiwar march to Paris. There is no doubt that the march is under heavy surveillance by the KGB security police. The marchers are allowed to carry the following banners: "No to Nuclear Weapons in the World" and "Yes to Disarmament and Peace."