Last week, an important anniversary went by far less noticed than it deserved: the twentieth anniversary of the death of one of the 20th century's greatest sons, the Russian dissident, human rights activist and scientist Andrei Sakharov. The loss was greatest for Russia, where the fledgling democratic opposition was deprived of one of its unquestionable moral leaders just when communism was collapsing. But Sakharov, the 1975 Nobel Peace Prize laureate, was truly a citizen of the world, and his legacy also has profound relevance to the West.

Sakharov, a physicist who was the father of the Soviet hydrogen bomb, first became a presence on the world scene a little over 40 years ago, in 1968, when his essay, "Reflection on Progress, Peaceful Coexistence, and Intellectual Freedom," was smuggled out of the USSR and printed in full in The New York Times.

"At the time, even to say that we needed democratization was a crime, because we were supposed to be the most democratic country in the world," fellow Soviet dissident and physicist Yuri Orlov recalled in October 2008 at a conference in Cambridge, Massachusetts on the anniversary of the essay's publication. Yet here was Sakharov, a member of the Soviet Union's privileged scientific elite, calling not only for better relations between the USSR and the West but for intellectual freedom and "democratic politics" within the Soviet Union itself.

The Soviet leadership responded first by trying to persuade Sakharov of the error of his ways, then by using threats and slander. But the genie was out of the bottle: the dissident movement, which Sakharov's act of civic courage helped spark, lived on. In 1980, the harassment of Sakharov and his wife and fellow human rights activist Elena Bonner culminated in internal exile to Gorky, a city closed to foreigners.

Yet the collapse of the regime Sakharov challenged was already near. In 1986, Mikhail Gorbachev, the new reformist head of the Soviet state, brought Sakharov back from his exile. Soon afterwards, the scientist was elected to the Congress of People's Deputies - but found himself marginalized by a majority that balked at such "radical" ideas as the abolition of Article 6 of the Soviet Constitution which enshrined the "guiding" political role of the Communist Party.

Tragically, Sakharov died of a heart attack on December 14, 1989, at the age of 68. Over 100,000 flocked to his funeral.

Twenty years later, one does not have to be a hardcore pessimist to feel that Sakharov's cause, at least for now, has been defeated in his native country. The hopes of the late 1980s, when freedom was in the air and change was rapid and exciting, has given way to the return of a repressive state, albeit with far more personal freedom than in Soviet times.

Many of Sakharov's former comrades-in-arms, such as leading human rights activist Sergei Kovalev, are once again political outcasts. His widow and fellow activist Elena Bonner, now living in the United States, has been an outspoken critic of Vladimir Putin's neo-authoritarianism and its continuation under Dmitry Medvedev. As in Soviet times, she has been the target of smears in the official Russian media - which pay respectful lip service to the memory of Sakharov himself. A program shown on Russian state television for the anniversary of his death focused on Sakharov's scientific work while portraying his political activism as incidental and all but ignoring Bonner, his indispensable partner.

Yet some in Russia believe that the country today is on the cusp of change just as it was when Sakharov came back from his exile, and that his ideas could be a beacon once again.

On December 14, at a Moscow conference commemorating Sakharov, Bonner's daughter Tatiana Yankelevich read a speech written by her mother (85 and too frail to travel) discussing the current relevance of Sakharov's ideas. Some of his views may seem dated, naïve, or questionable to many of those who welcomed communism's fall - such as his view that a "convergence" of capitalism and socialism was a desirable goal. But Sakharov also advocated nuclear energy as a way for Western democracies to achieve energy independence and protect their freedoms, staunch support for Israel's security, and a drastic reorganization of the United Nations - which he saw as a flawed child of post-World War II Stalinist diplomacy, often stacked against the free world.

Sakharov's core belief, however, was that politics must be based on moral principle. While he was a strong champion of better relations between the United States and Russia - or, in his day, the Soviet Union - his vision included an unapologetic linkage of this goal to the furtherance of human rights and political freedoms. That is something both the Obama White House and its predecessor have often seemed willing to sweep under the rug in the quest for partnership with the Kremlin.

At last year's Cambridge conference on Sakharov's work, Harvard physicist Richard Wilson made a memorable comment: "Both the U.S. and Russia today need Andrei Sakharov: his intelligence, his wisdom and humanity, and most important, his ability to stand up to his government and say no." The moral issues of 21st century politics are not nearly as clear as they were in Sakharov's lifetime, when flawed democracy was pitted against soul-destroying tyranny. And yet there is much in his message that the world ignores at its own peril.