The dramatic events of recent days in Moscow have underlined for us once again that in foreign affairs it is much better to focus on principles and policies, rather than personalities.

Whether Mikhail Gorbachev falls or survives is, of course, a gripping human drama. But the critical question is not the fate of any one politician. The critical question is whether the Soviet Union, with its restless republics and unwilling satellites, is to retreat into darkness or continue its halting quest for political and economic freedom.That is going to depend on the will of its people. Is there something in the Russian psyche that will inevitably thrust the Soviet Union back into a bleak world of fear, conspiracy and dictatorship? Or has the whiff of freedom so exhilarated and emboldened its people that they are ready to hold at bay the conservative bureaucrats, the army's tanks and the agents of the KGB?

On the positive side, there is a wealth of evidence that the Soviet Union is much changed for the better. It has set Eastern Europe free, and such is the fervent embrace of democracy in such countries that there can be no turning the clock back.

In the Soviet Union itself, the fact that Eduard Shevardnadze could stand up in public, renounce his foreign ministership, criticize Gorbachev and warn of impending "dictatorship," proves that the Soviet Union has advanced light years from the fear-ridden regimes of Stalin, and even Brezhnev and Andropov.

Then there is the passionate public self-examination of processes and practices in the Soviet Union unleashed by Gorbachev's move toward reform. Communism has failed and is being replaced, with halts and starts, by ideas from the West. But the hard lesson the conservatives have been learning is that economic freedom and political freedom go hand in hand.

Marvel, then, at the frankness with which Soviet citizens speak out every night on American newscasts. A Moscow housewife, scrambling for scarce food, thinks nothing of telling an American television crew that her government is messing up the economy. In the lobby of parliament, legislators discuss Gorbachev's prospects with breathtaking freedom.

It is difficult to see how all this can be turned off.

But there are negative factors, too.

In sacrificing himself politically, Shevardnadze, apparently believing that Gorbachev's reform movement is at a watershed, seemed to send several dramatic messages. To his old political colleague Gorbachev, he seemed to be warning of indecision while problems linger. To the reformers of the left, he seemed to be warning that they lack cohesion. To the hard-liners of the right, he seemed to be warning that the tide of history is against them.

While the United States waits to see whether his startling gesture will have a positive effect, it should support constructive forces for change in the Soviet Union but remain alert to the possibility that the Cold War could return.