ITHACA, N.Y.— How are we to reconcile the contradictory images of Mikhail Gorbachev? Should we think of him as the great liberator of Eastern Europe and recent winner of the Nobel Peace Prize or as the demagogue who has sent tanks into Latvia and Lithuania and demanded the restoration of press censorship? Were perestroika and glasnost one more mirage in a long tradition of Russian deceptions dating all the way back to Potemkin's villages?

The West's bewilderment in the face of his latest turnabout is understandable, if only because of our tendency to personalize politics and worship personalities. Yet informed observers have been reporting for months that Mr. Gorbachev was far less popular in his homeland than in the West.

For some Soviets, the problem was precisely perestroika and glasnost. Supporters of the old order detest these policies and blame them for the current bankruptcy of the regime. Accord ing to a prominent conservative critic, Mr. Gorbachev will be damned for millenia because the "emperor of perestroika" is naked.

For Soviet liberals, the problem has been the reverse. When securing perestroika has required decisive action, Mr. Gorbachev has balked. Last fall, he reneged on Stanislav Shatalin's 500-day plan for economic reform. Just as damaging has been his chronic inability to implement an effective nationalities policy. Had his recent attempt to set up a Nationalities Council occurred two years earlier, it might have headed off the current tragedy in the Baltics. Now the proposed council is irrelevant.

Mikhail Gorbachev as Hamlet? Certainly his indecisiveness has a long history, dating back to his hesitation to submit himself to a popular vote for president, even though he would have won handily. Two years ago already, Andrei D. Sakharov perceived Mr. Gorbachev's dilemma and warned that the Soviet leader would eventually have to choose between perestroika and the state apparatus.

Has Mr. Gorbachev then made his choice? Or is he a prisoner of conservative forces and therefore not personally responsible for the shootings in Latvia and Lithuania? It is hard to tell. The trend toward a reversal of perestroika and glasnost started last fall with the rejection of the Shatalin plan and a campaign against the liberals in the Soviet media. Mr. Gorbachev has progressively accumulated power, while steadily ridding himself of his liberal advisers and replacing them with yes-men and apparatchiks. Foreign Minister Eduard Shevardnadze's resignation, which pre-empted his almost certain dismissal, was only the most visible confirmation of this process.

Until now, Western commentators have generally concluded that Mr. Gorbachev's playing of left against right was part of a classic political balancing act on the Western model. Others have noted that his tactic of veering left and right to get rid of rivals was used by Lenin and Stalin. The authoritarian and conspiratorial nature of Soviet politics invites such stratagems and it would not be surprising if a seasoned Communist such as Mr. Gorbachev instinctively fell back on similar ploys. However, Mr. Gorbachev is a hybrid: a traditional Soviet leader steeped in Communism who nevertheless has aspired to behave as a liberal democrat.

What has been consistently overlooked in the debate over President Gorbachev's true intentions is the nature of his personal political philosophy and the beliefs that drive his policies. Mr. Gorbachev is not just a product of the Communist Party apparat, as so many have pointed out, and therefore a cynical manipulator.

President Gorbachev is also an idealist (as his quixotic campaign against alcoholism demonstrated) and a member of that almost extinct species, a true believer in Communism. Not the Communism of Stalin and Leonid Brezhnev, of course, nor even quite of Nikita S. Khrushchev, but certainly of Lenin.

When Mr. Gorbachev first came to power in 1985, he revived the Khrushchevite slogan of a "return to Leninist norms." Liberals both East and West later persuaded themselves that this was a tactical move to discredit Brezhnevite neo-Stalinism and that once a certain amount of progress had been achieved Leninism could be dumped as well.

But Mr. Gorbachev has dumped neither Lenin nor Communism. To be sure, he was prepared to remove the word "socialist" from the name of the country, but this was a sop to the nationalities. He has never expressed less than total conviction that a future Soviet Union will be Socialist and controlled by the apparat. He has been consistent in this belief, starting with his book "Perestroika" and ending with his recent comment that the Lithuanians wished to introduce a "bourgeois" form of society.

When we look at Mr. Gorbachev in the context of these beliefs, his policies take on a new coherence. His goal was a return not to capitalism or even social democracy but to something resembling Lenin's New Economic Policy of the early 1920's: a limited and guided system of free enterprise with the commanding heights of the economy still controlled by the state and the party.

Jettisoning Eastern Europe was not a foreshadowing of what was to happen in the Soviet Union but rather a means of preserving the Soviet Union and its Socialist form of society. Letting the Eastern European countries go was different from allowing any of the states in the original union to secede. Lenin put that union together and Mr. Gorbachev does not wish to go down in history as the man who destroyed Lenin's legacy.

This, therefore, is the tragedy of the Soviet President. He wishes to improve the lot of his countrymen, to bring them wealth and prosperity, and even democracy up to a point, but within a Socialist context. This explains the swings from left to right and the reason he has consistently balked every time the central power of the apparat has been called into question. Now Mr. Gorbachev has been persuaded by the hardliners that the only way to preserve the union and the machinery of state is the iron fist.

Perhaps he will be able to perform another miracle and extricate himself from the Baltics without more bloodshed. I suspect, however, that his days are numbered. If the conservatives regain power, they will almost certainly replace him with someone more decisive and with fewer ideals. As for the liberals, they will never trust him again.