THE GREAT difference between Hungary 1956 and Lithuania 1991 is that Hungary was alone and Lithuania is not. In the Hungarian case, the rest of the world stood back, horrified by the spectacle of Soviet tanks crushing freedom but unable to compose a response that did not seem to threaten the greater horror of a European war. So few were the strands existing then between East and West, moreover, that there was little to cut off to signify the West's revulsion. The Hungarians felt abandoned, and they were.

In the case of the Baltics now, it is inconceivable as a practical matter that the countries of the old West or of the old Eastern Europe should intervene militarily. But it is certainly conceivable that these countries should cut some of the ties that have been put in place in the last few years between them and Moscow. A feeling of having been let down, even betrayed, by the Gorbachev leadership and a fresh determination to stand symbolically with the Baltics: these sentiments mark the discussion that is now proceeding on which of these ties to cut.

Unless Mikhail Gorbachev's government has completely abandoned its strategy of reviving the country with infusions of Western advice, capital and aid, it is bound to pay some attention. Perestroika after all is not simply a self-help movement but a program for reaching out and accepting a crucial measure of foreign dependence. A country intending to modernize by opening up to the West had to figure on forgoing Stalinist techniques of imperial control; otherwise it could not expect to keep the West engaged. This is the trap that Mr. Gorbachev may be closing on Soviet reform now.

Lithuania's friends are not only or mainly in the West and the old Eastern Europe. Unlike 1956, when central discipline reigned, help is available from the other Soviet republics, first of all Russia, which is the largest and which has in Boris Yeltsin a leader of stature. Mr. Yeltsin has denounced the Soviet assault on Lithuania and expressed solidarity with the Baltic republics. He has called on Russian soldiers to take no part in military action there and has started planning to establish security forces and perhaps even an army of Russia's own. Further Soviet moves in the Baltics can only deepen his and other republic leaders' already strong nationalist impulses. This is a tremendous price for the center to pay to deny the independence claimed by and due to the Baltic nations.

Mr. Gorbachev says that Soviet society is moving right -- and presumably he with it. Mr. Yeltsin says no, society is becoming "more politicized, in favor of democrats." This is the great political question being played out in Lithuania and across the Soviet land.