Isaiah Berlin did not live to see these new tyrannies arise in Russia and China, and he would have trouble recognizing the world we now inhabit - post 9/11, post-meltdown, post-liberal in so many ways - but he did know a lot about living beside barbarians. His Cold War liberalism has much to teach us still.

The first lesson, as the 19th century Russian writer Alexander Herzen said and Berlin liked to repeat, is that history has no libretto. We should not assume there is any historical inevitability to liberal society, anymore than it made sense to predict in 1950, say, that both Chinese and Russian totalitarianism were doomed to crumble. Since no one predicted the direction these societies have taken, no one can be sure that either will evolve toward anything remotely like a liberal democratic order.

To say that history has no libretto is not a counsel of pessimism. Berlin's historical humility was always paired with a strong belief in the efficacy of freedom. Leadership, he knew, could bend the arc of history, if not always toward justice, at least away from tyranny.

If this is true, then in our dealings with the Chinese and Russians, it matters to give help to those who campaign for the rule of law, not the rule of men, who want poor villagers to be fairly compensated for expropriations of their land, who want ordinary people to have the right to read anything they want on the Internet, who want free and fair elections and an end to the rule of billionaire oligarchs.

History is not necessarily on the side of these liberal values, but fighting for them remains a moral duty. We do this because history is on nobody's side, and freedom needs all the help it can get.

If this seems a defiant stance toward the new tyrannies in China and Russia, and it is, then we need to learn from Berlin how to balance resolution toward tyranny with openness toward what these societies can teach us. This balance between firmness and openness is the equilibrium the liberal temperament is always seeking and a liberal foreign policy should always aim for.

While liberal tolerance can look a lot like appeasement, Berlin shows us how it is possible to combine tolerance with firmness. The true pairing of tolerance should be with curiosity, with an appetite to learn from beliefs we cannot share.

The larger point is that Berlin thought it was dangerous to organize one's mind into fixed and immovable categories of "us" and "them", still worse to believe that without a "them" there can be no "us".

Liberals refuse to treat opponents as enemies. They see their antagonists differently, as persons who must sometimes be opposed, and with force if necessary, but also as persons who might be persuaded to change their minds, and who, in any case, must be lived with, if they cannot be changed.