On the front cover of this characteristically rich and insightful book by Tzvetan Todorov the subtitle is "Reflections on the Twentieth Century", while on the title page it becomes "Lessons from the Twentieth Century". This is merely inconsistency on the part of translator and editor; it denotes no wavering of aim on Todorov's part - for reflections often yields lessons, even if sometimes what they teach is that the past is no guide to the future.

In this case, though, the lesson is that the twentieth century indeed has much to teach - not least about the nature and uses of historical memory, and about the significance of individuals who face historical cataclysms with the special attitude Todorov calls "critical humanism", and by doing so carry the light of the best human possibilities through the darkest times.

Todorov's ambitious and wide-ranging aim is to survey the titanic clash between totalitarianism and democracy in the twentieth century, and then to examine the place of memory and history in making sense of that clash. This is done not just from the perspective of the aforementioned lessons, but by considering how memory and history were themselves manipulated by the century's totalitarianisms, one point of doing which is to remind ourselves that both memory and history have many uses and can be applied in many different ways.

The book was written before 9/11 and therefore Todorov adds a supplementary preface to this English edition in order to bring the atrocities of that date within its purview. Interestingly, the book gains from having been written outside the shadow of those events; as Todorov was writing it the pressing contemporary concern was Kosovo, which therefore occupies a substantial part of the book's horizon, but with valuable lessons of its own to impart. The book's primary focus is Europe in the twentieth century, whereas 9/11 is an American and global event; but Todorov shows that for America the memory-lesson of that event is the same as for Europe or anywhere else: "we learn more from our mistakes than our good deeds. Thanks to them, we can begin to moderate pride with humility - and to see that, very often, the best way of defending our own interests lies in not neglecting the interests of others."

Todorov's first two chapters concern the nature of both totalitarianism and democracy and the conflict between them. The last three concern memory and history. Between the chapters are excursi on the six "critical humanists" whom Todorov applauds as emblematic of the human spirit's resistance to the century's evils: the Russian-Jewish writer, Vasily Grossman; that extraordinary witness of the century's oppressions, Margaret Buber-Neumann; the French writer and campaigner, David Rousset, whose experience of concentration camps under the Nazis later led him to campaign against the Soviet gulag; the brilliantly insightful novelist Romain Gary; the camp survivor and Algerian War campaigner Germaine Tillion, and Primo Levi.

For Todorov a humanist or "critical humanist" is a philosopher of democracy, and therefore a pragmatist. Humanists know that no knowledge can ever be claimed as final and definitive, and therefore no "-ism", including "scientism" (the belief that science will explain everything and solve all problems), is going to yield final answers and bring heaven to earth. Instead, humanism promotes an attitude towards humanity premised on the principle that all people have the same rights, and the same claim to respect, no matter whether or not they live in the same ways as each other. There will be no paradise on earth because there is evil in man and the world; but these things are "of one substance" with human life because they arise from our freedom to choose. But human sociability and incompleteness can lead us to cherish one another, which implies a refusal to treat one another merely as means to ends. Of course, the ever-present risk that people will prey on each other rather than cherish each other means that there can be no utopia, no global and final solution to the problems of human existence. But at least humanism invokes the hope that people will see and treat others as individuals, not as objects or mere label-bearers of one kind or another; and in that hope lies the best future for mankind.

In his earlier writings Todorov described the human realm as an "imperfect garden", and he is here reprising this view. His humanism is down to earth, pragmatic, and rather world-weary. It does not sing mankind's praises without qualification, because it recognises his failings and his capacity for evil. But through their capacity for freedom of choice people are also capable of cherishing each other; and that is their salvation, so far as salvation is possible. This is why humanism has affinities with democracy, because the humanistic impulse towards community and fraternity gives individuals their best chance of flourishing.

That is one great lesson Todorov draws from his examination of the twentieth century. The other concerns memory itself. Our choice is not between remembering or forgetting the horrors of totalitarianism, he says, because forgetting is not something we can do by an act of will. Rather, the choice is between different ways of remembering. The kind that can best help in facing the future neither trivialises the past nor makes it sacred in some way. What memory of the twentieth century, thus viewed, teaches is that democracy (or humanism: the terms are convertible in Todorov's lexicon) faces three dangers: too much identity politics, too slavish an adherence to "moral correctness", and "overinstrumentalisation" in the sense of too great focus upon means rather than ends. Overcoming these three dangers does not guarantee individual flourishing, but is a necessary condition for it; and a focus on individual flourishing is itself the best defence against a return to the totalitarian horrors of the last century.

Such is the tenor of Todorov's absorbing book. As with all works of ideas it offers much to debate, even to disagree with; but even more to learn from, and to profit by.