THE SPIRIT of modern nationalism has been the strongest emotional political force in the Western world over the last 150 years. Closely connected as it has been with the sense of linguistic identity, it was bound to be disruptive of the great multi-lingual and multi-national empires that played such a role in European life for several centuries: and most of them, indeed, disintegrated largely under its impact before the middle of this century.

The Russian Empire was as vulnerable as any other to these pressures and there was no reason to suppose that it, any more than the others, would be able to stand out indefinitely against them. And indeed, when it was shaken by the first of the two revolutions of 1917, there was a time when the empire's break-up appeared to be imminent. Actually, the jealous and ruthless power of the Communist dictatorship, introduced by the second of those revolutions, sufficed to hold most of the empire together.

But the three Baltic countries, which for two centuries had existed as semi-autonomous dependencies of the Russian crown, did succeed at that time in breaking off and establishing their independence; and for two decades thereafter, until World War II, they carried on with reasonable success as independent countries. The war, however, put an end to all this. After their territories had been overrun successively by the Russians, then the Germans, then the Russians again, the Baltic peoples, now ravaged, helpless and exhausted, were re-included into the post-war Soviet version of the traditional Russian Empire, where, to their intense unhappiness, they have been ever since.

The drastic weakening of the Communist dictatorship that has been the accompaniment and the achievement of Mikhail Gorbachev's regime, has now once again released the centrifugal forces within the empire. The pressures for an extensive decentralization of the Soviet state, and sometimes even for its total break-up, have come forward with a vehemence greater than anything seen in the past. In the forefront of this movement have been, of course, the demands of the three Baltic peoples for complete independence.

The passionate intensity driving these demands is evident on every hand; and there can be no question of their justification. Alone among the rest of the non-Russian nationalities of the Soviet Union, the Latvians, Lithuanians, and Estonians have had the opportunity to demonstrate, in their 20 years of independence, their ability to meet the responsibilities of independence. Any effort now to deny them indefinitely the independence they long for and are determined to achieve would not only bring far greater difficulties than advantages to the central Soviet authorities, but would probably fail in the long run anyway. Whatever may be the case elsewhere in the Soviet Union, this particular cat is out of the bag and will not easily be reinserted into it. It is true that the Baltic leaders, particularly in Lithuania and Latvia, have not always made things easy for Gorbachev. Their demands for instant recognition of their independence, prior to any orderly negotiation of the contingent questions, and the impetuous actions by which those demands were sometimes supported, have not eased the process of transition. Nevertheless, things have now advanced to a point where the wisest policy for the central Soviet authorities will be to cut their losses in that region, concede to these peoples on principle the independence they want, and go on from there to negotiate the many aspects of this separation which will require formal understanding between the respective parties.

It is inconceivable that the Moscow leaders should not see this. Indeed there is much evidence that they do. But there is also no evidence that the necessary consequences have all been drawn.

This being the case, the bloody episodes that have occurred in Vilnius and in Riga in recent weeks make no sense at all. Frivolous, erratic and provocational, insufficient to achieve any positive result but just sufficient to get everyone's back up in the affected republics and in the Western world, these adventuristic and apparently undisciplined actions have served no useful purpose, but every conceivable mischievous one.

They have not, contrary to the lurid exaggerations that have appeared here and there in the Western press, constituted a serious "crackdown" on the countries in question, comparable to what took place in Hungary in 1956 or in Czechoslovakia in 1968. In most respects political life has continued in Lithuania and Latvia much as in recent months, which means: with the continued actual enjoyment of a degree of independence that would have seemed, as little as five or 10 years before, almost inconceivable. The principal significance of these recent episodes has lain rather in the revelation they offer of a state of truly alarming incoherence and lack of coordination in Moscow itself, leading the other Western governments to ask themselves whether any sort of serious and effective central authority exists at all in that city.

The situation that prevails in the Soviet Union at large there is both dreadful and dangerous. If it is true, as it appears to be, that the supply of consumers' goods to the larger cities cannot be assured without the wholehearted collaboration of the party apparatus and the armed units in the great rural hinterland of the country, then one could understand why Gorbachev has felt himself compelled to reach back at this time for the support of those institutions. What is required, on the other hand, for the great cities is probably something quite different. One is thrown back here on those basic causes that have frustrated Russian reforms repeatedly over recent centuries: the great difference between the perceived needs of the backward, primitive Russian countryside and those of a more highly educated, enlightened and westernized urban centers.

Gorbachev has shown little or no evidence to date of an ability to master this situation and to create an effective central government authority. Some of this may be attributable to his own deficiencies but much would appear to be inherent in the situation. And if there is any other personality on Russia's political horizon who would show greater promise than Gorbachev has shown of coping with this situation from the position of a central Soviet authority, this writer does not know who this could be. This being the case, it is a real question whether what we know as the Soviet Union can any longer be effectively governed from a single center at all, except possibly in a very few respects where some continued central coordination is indispensable. If it cannot be so governed, then the only possible route of advance toward the restoration of order and economic vitality would appear to lie with the heightened autonomy, at the very least, and perhaps the limited independence, of some of the 15 constituent republics. One will have to yield extensively, in other words, to the demand for a real and far-reaching decentralization of the traditional empire.

Gorbachev appears not to realize this; and indeed, it is hard to see how he could retain his pre-eminence in a country so decentralized; for he has pinned his flag firmly to the maintenance of a highly concentrated central authority, and his position can only be weakened by the disintegration of that authority.

This writer, like many others, would regret such a change in Gorbachev's personal position. He is one who in earlier years rendered great and historic services to the Soviet people. But if it turns out that confidence, discipline, and vitality can be restored to this great country only through the relatively independent efforts of the various republics, this could be the price that would have to be paid for the achievement.

These problems are of immense importance for the future of the traditional Russian state. It is the peoples of that region that will have to find, albeit probably with much pain and difficulty, the solutions to them. Outside pressures are not apt to be either effective or useful. President Bush and Secretary of State James A. Baker III have been wise to take the long-term view of the situation and to avoid shaping American policy solely with a view to the recent unhappy events in the Baltic countries. There will be further need for such restraint as this historical readjustment of the inter-relationships of the peoples of that region proceeds; and it is by the observance of such restraint that our influence will most usefully make itself felt.

George F. Kennan, former United States ambassador to the Soviet Union, is Professor Emeritus in the School of Historical Studies, at the Institute for Advanced Study, Princeton, N.J.