THE SOVIET OBSESSION with secrecy limits outsiders to frustrating speculation about the Kremlin's real foreign policy intent, where answers are contingent at least as much upon the individual biases of the analysts involved as on the glimpses of Soviet reality available to them.

Hence the hunger for definitive answers from someone ostensibly in a real position to know. And who is better qualified to address Soviet foreign policy intentions and policymaking procedures than a highly-place defector? Enter Arkady Shevchenko, the highest ranking Soviet diplomat ever to defect to the West since World War II. In 1978, before he asked for political asylum in the United States, Shevchenko served as a United Nations undersecretary general. Even more interesting, from the standpoint of access to the Kremlin, was his prior service as an adviser to Soviet Minister of Foreign Affairs Andrei A. Gromyko, who has recently emerged as the principal architect of Soviet foreign policy.

There is no question that Shevchenko was privy to significant information and his account makes an important contribution to the West's understanding of Soviet foreign policy aims. Yet several early reviews of his book Breaking With Moscow have raised doubts about Shevchenko's credibility. The issue is not whether he is loyal to his new country the United States. That much anyone except those stricken with paranoiac suspicion should consider established. For three years until his defection, Shevchenko spied for America at an enormous personal risk. His changing of camps was a great embarrassment to the Politburo. And U.S. officials intimately familiar with Shevchenko's file vouch for his bona fides. What triggered much unfavorable commentary was not Shevchenko's political integrity but rather his personal character. And the book provides ample grounds for concern on this score. To start with, Shevchenko fails to explain credibly why he defected. He was disillusioned with the system. But so are most Soviet citizens. Very few defect. Shevchenko admits that his U.N. colleagues regarded him "as an orthodox Soviet functionary, obedient, loyal, a hard-line Communist." And the image was not entirely wrong. In Shevchenko's own words, "I had never fought my government the way dissidents did. On the contrary, I served it loyally as well as I could for many years." So what did finally convince him to break with Moscow? The book sheds little light. Was he, in addition to feeling alienated from the regime, also dissatisfied with his family life? Did he feel that his career had gone sour? After all, Shevchenko states that the Soviet government does not regard the U.N. secretariat highly. So an appointment to move there could be viewed by Gromyko's ambitious adviser as a kick upstairs? Finally, could he have been entrapped by U.S. intelligence? According to Shevchenko, he was asked to spy for America only after inquiring privately about the possibility of receiving political asylum. There is almost certainly more to the story.

THERE ARE also problems with Shevchenko's account of the circumstances which led to the death of his wife. He suspects that the KGB may have murdered her because upon her return to Russia she probably "made herself a threat to several careers." Perhaps. Yet Shevchenko offers no supporting evidence. And why would the KGB, with the Gulag and mental health institutions at its disposal, need to create an unnecessary controversy by killing a woman already back in Moscow and thus firmly under control? The official Soviet version of Lina Shevchenko's death -- suicide -- does not sound completely implausible. The poor woan woke up one morning in her New York apartment only to discover a note from her husband informing her that he "intended to ask for political asylum in the United States." Her shock is easy to imagine. It probably was soon followed by a nightmare of KGB interrogations, fearful emotions and a realization that her whole life had been suddenly destroyed. Needless to say, it was the Soviet regime that had driven her to suicide. But Shevchenko, who opted to escape to his CIA handlers, while leaving her alone in the couple's New York apartment, asleep and ignorant of his plans, does not look like a knight on a white horse either.

Similarly, Shevchenko expresses little or no remorse for the many political and moral compromises he presumably had to make in order to rise through the ranks of the government he increasingly despised. Shevchenko is openly proud of his impressive career in the Soviet foreign policy establishment. The trouble is that merit alone rarely assures success in the Soviet bureaucracy. "If Machiavelli were alive and living in Moscow today, he would be a student, not a professor," Shevchenko writes. Yet, there is nothing in the book to indicate that the author had to engage in anything distasteful before his decision to defect. Should the reader assume that the former diplomat managed the remarkable feat of entering the ruling class with clean hands?

Breaking With Moscow is anything but a confession. These are not the memoirs of a man eager to explain his inner transformation. One key to understanding the Shevchenko book is realizing that it is written by an ambitious person anxious to establish himself as a major voice in American public debates on relations with the Soviet Union. Ambition is, after all, one reason he agreed to become a U.S. spy. He "thought, to work for the Americans for a while would be the most effective way of dissipating any doubts they might have about my honesty and sincerity." Otherwise, if he did not prove to be sufficiently cooperative, Shevchenko was afraid that the U.S. authorities might throw him away, "like a squeezed lemon." He certainly "hoped for more than that" in terms of his career prospects in America.

To some moral purists such frank pragmatism may sound offensive. But before condemning Shevchenko, one should be aware of a possible double standard. Should the same demanding criteria be applied to the memoirs of recent presidents, secretaries of state and national security advisers? If so, Shevchenko's selective memory and self- serving attitude would not look too bad. Personally, I wish he had skipped the details of his illustrious life and his final defection and concentrated entirely on what is really interesting in his book -- the Soviet foreign policy process. But then, of course, his book would not have become a best seller. And in all fairness, any publisher would pressure a celebrity defector to tell his personal tale even at the price of serious distortions.

IT IS UNFORTUNATE that the controversy over Shevchenko's own story distracted somewhat from the attention of his real substantive message. And that message is both important and basically credible. Breaking with Moscow offers new insight into how Soviet foreign policy decisions are made, who makes them and with what purpose in mind. Shevchenko explains that the Soviet leadership views the East-West relationship and the international political process in general "in terms of the continuing struggle between two opposing social and political systems." And they believe that eventually "their system is going to prevail." In this respect they are not very different from Ronald Reagan. And like Reagan, "they do not intend to achieve this victory by resorting to nuclear war."

How do the Soviets expect to triumph without resorting to nuclear war? According to Shevchenko, they are not quite sure themselves. He reveals, for instance, that "while short-term global political goals are obvious to the top echelon of the Foreign Ministry, long-term policy planning is almost nonexistent." Instead, Soviet policy makers have their hands full in dealing with immediate challenges to their empire and exploiting immediate opportunities available to it. Both are in abundance. As Shevchenko sees it, Russia's rulers are extremely cynical and heavy-handed. They would stop at nothing -- including assassination -- as long as they are sure that they can get away with it. But risk- taking is not one of their qualities. When the Politburo engaged in a dangerous adventure it was not the result of some sinister master plan -- but the outcome of escalation and miscalculation.

He reveals, for example, that the 1973 Yom Kippur war took the Soviet government by surprise. And the U.S.S.R. simply had no choice but to fulfill its obligations to the Arabs. Otherwise, he explains, "Moscow might have substantially undermined its position in the Aab world." Likewise in the case of Angola, "the idea for the large-scale military operation had originated in Havana, not in Moscow."

And almost everywhere the Soviet leadership's primary concern was avoiding a direct confrontation with the United States. It was America's lack of resolve that contributed to the Soviet expansionist drive in the mid-'70s. The Soviets were most surprised that the United States -- a superpower -- accepted defeat in Vietnam. And the American humiliaton was perceived as an "argument for a much tougher line with the capitalist world, especially with the United States." Similarly, Soviet activism in Africa was encouraged by an image of America "as a diminished rival in the Third World."

THE IMPLICATION Shevchenko draws for U.S. foreign policy is both clear and sound: Soviet global ambitions can be constrained only by credible deterrence and by the Western will to defend its important interests. Still, Shevchenko is not a Cold War ideologue. He is for a constructive relationship with Moscow from a position of strength. His advice is "to seek a reasonable and pragmatic accommodation, even cooperation, where our interests are in alignment." And his book contains a number of instances when the Soviets were genuinely interested in mutually beneficial arrangements, primarily in the area of arms control.

Shevchenko's portraits of senior Soviet diplomats such as his former boss Gromyko, Ambassador to the United States Anatoly Dobrynin, and U.N. ambassador Oleg Troyanovsky are colorful and realistic. They are described as highly competent, pragmatic servants of the Soviet regime. Incidentally, Shevchenko deserves credit for dissuading the Reagan administration of the notion that Gromyko has strong anti-American instincts and was a major obstacle to improving the U.S.-Soviet relationship. In fact, because of his long association with diplomacy toward the United States and his Realpolitik mindset, Gromyk seems to be committed to dialogue with America -- in order, of course, to advance the Kremlin's interests. But what counts is that Gromyko "understands that it is in Moscow's interest to establish normal relations, no matter who is President and whether Moscow likes him or not." Shevchenko confirms the opinion of Western Sovietologists that a considerable fragmentation of power occurred during the Brezhnev rule. From his standpoint, the foreign ministry under Gromyko was transtormed from an implementor into an architect of Soviet power toward the West. Shevchenko "cannot remember a single case when the Politburo failed to adopt a ministry proposal." Whether Gromyko and his ministry will enjoy similar power under the vigorous leadership that can be anticipated from Mikhail S. Gorbachev will be interesting to watch.

Some of Shevchenko's judgments appear to me less persuasive. His suggestions that an air crash which killed U.S. Secretary General Dag Hammarskjold was a Soviet-directed assassination and that the Soviets attempted to assassinate Egyptian President Anwar Sadat, are not based on firsthand information -- he claims no access to the KGB's most intimate secrets -- but rather on vague banter in Moscow corridors of power. The talk is disturbing, but as anyone familiar with the gossip that pervades the Soviet capital knows, it is clearly insufficient for drawing conclusions. Also, one can question Shevchenko's dismissal of Georgy Arbatov -- director of the U.S. and Canada Institute and a frequent guest on American talk shows -- as an irrelevant propagandist. That has been Ambassador Dobrynin's position all along and may reflect resentment at the foreign ministry of Arbatov's enterprising personal diplomacy.

Breaking With Moscow tells a lot about Soviet foreign policy and its architects. It also tells a lot about Arkady Shevchenko, an ambitious hard-nosed man with common sense and a good gasp of international issues. If Gorbachev will surround himself with people of such caliber, the conduct of Soviet foreign policy will become much more effective. But whether that will work to benefit or harm the United States is anyone's guess.