Soviet dissent seen form outside and from inside the USSR; On Soviet Dissent: Interviews with Piero Ostellino, by Roy Medvedev. New York: Columbia University. $10.95.

Many Western observers view the Soviet dissidents as an undifferentiated group ideologically united in its brave opposition ot Soviet oppression. In reality, Soviet dissent is highly diverse and contradictory: Small factions argue fine points of morality, socialism, and democracy even as they are led to the prison doors. There may not be many of them, but Russia's dissidents are as subtly different from one another as the worn cobblestones of Red Square.

Roy Medvedevhs "On Soviet Dissent," a series of recent interviews with the Italian jounalist Piero Ostellino, one-time Moscow correspondent for Corriere della Sera, reveals this diversity. Medvedev, a Soviet historian and author of many books, including "Let History Judge" and "On Socialist Democracy," emerges with remarkably objective perceptions on his fellow dissident movement since Khrushchev. Here is none o the hysteria and extremism one has often come to expect of Russian political thinkers -- both dissident and official. Medvedev, who calls himself a socialist democrat, is well aware of the profound shortcomings in the Soviet political system -- but he also sees its advantages.

Medvedev believes that socialism can work. He recognizes that the most serious flaw in Soviet communism is its lack of tolerance for political viewpoints other than those espousedby the Communist Party; he advocates what he calls socialist pluralism. He also believes the Soviet Union is capable of change -- that it is not doomed forever to a gloomy totalitarianism.

Russina intellectuals have long been divided between those who look to the West for governmental models, believing that they can be adapted to Russian uses , and those who believe Russia is so profoundly different that it has nothing to learn from the West. Medvedev, true tohis democratic beliefs, looks to the West , and holds the Russian people responsible in some measure for the government that rules them. "[They] are more submissive than they need be," he says.

For a man who has been prsecuted and hounded in the name of his country (Medvedev, perhaps because of his relatively moderate views, has not been threatened -- yet -- with exile), Medvedev remains remarkably balanced and patriotic. He pays tribute to members of the Soviet establishment, such as Alexander Tvardovsky, former editor of Novy Mir, where Solzhenitsyn's "One Day in the Life of Ivan Denishovich" was published., who have struggled from within rather than becoming dissidents. "Perhaps they did more to awaken and push forward the positive selfawareness of our society than many dissidents of that decade who were widely publicized in the Western press."

Medvedev admits that the movement that first flowered under Khrushchev in the early 1960s has wilted in the '70s. But Medvedev, ever an optimist, has hope for the future. A new generation of dissidents is growing, he says, students "who have looked on and come to know the tremendous hardships dissent entails. . . . They're trying to work with greater profundity." One thing is certain: As long as dissidence exists in Russia, Roy Medvedev will be a desperately needed voice for sanity and compassion.