One way to learn the value of something important whose possession we normally taken for granted is to lose it. Another, better, less painful way is to imagine its loss with the aid of books. And to know the value of freedom, we have to understand the horror of unfreedom.

Officially, we all value freedom of speech, but the Anglo-American defence of it during the recent furor caused by the Danish cartoons has been timid and lukewarm, to put it mildly. We need to remember how freedom is lost, and what it is like to live where it has been lost.

Sebastian Haffner's memoir, Defying Hitler (Weidenfeld & Nicolson, 2002), was not published during the author's lifetime. Haffner died in 1999, at 91, after a distinguished career as a journalist. The son of a non-Jewish Prussian civil servant, and trained as a lawyer, he left Nazi Germany for England in 1938, and wrote his memoir in 1939, but left it unpublished in a drawer.

The memoir tells the story of a normal, decent young man, without strong political convictions, who observes the ascent of the Nazis. Freedom is lost because there is no resistance to its loss: Everyday life continues as if nothing extraordinary were happening when everyone knows that it is, but is too afraid to say so. Little compromises with political criminality lead to ever bigger ones; for, as one of Haffner's legal colleagues puts it, "There's a sharp wind blowing." It is pointless or dangerous to resist this wind: the only sensible thing is to give into it by going in its direction. Pragmatism becomes surrender.

People are changed by their surrender. "By acceding to the rules of the game that was being played with us, we automatically changed, not quite into Nazis, but into usable Nazi material." Eventually, there was nowhere to hide: "We were pursued into the farthest corners of our private lives." To remain even minimally decent, one had to be either a hero or suicidal.

The book is impressive because Haffner does not present himself as such a spotless hero. He himself makes compromises and in the end all he can do is flee, there fortunately being somewhere he can flee to (the Islamists would like to ensure that this were not so). His point is that when there is no critical mass of the population to defend freedom, and when people ignore the threats because they want a quiet life, freedom is extremely vulnerable.

A few years earlier, Stefan Zweig had written The Right To Heresy: Castellio Against Calvin (Viking Press, 1936). Zweig was a great Austrian writer who, for some reason inexplicable to me, has never really caught on in the English-speaking world. Born into a wealthy Viennese Jewish family in the latter part of the 19th century, and immensely cultivated, he wrote a series of novels and novellas (Beware of Pity, Twenty-Four Hours in the Life of a Woman and Amok, among many others) that explore human passion with immense understanding. Perhaps he has never really taken off in the English-speaking world because he is too serious for those who read mainly trash, and too compulsively readable for the literati.

He lived a loss of freedom in his own flesh and bone. The Nazis burned his books; he fled to Britain, became a citizen and then moved to Brazil where, in 1942, he committed suicide with his wife, convinced that the Nazis and their barbarism would triumph everywhere.

Besides being a novelist, he was a great biographer. His biographies were always related to the problems of the time. In The Right to Heresy, written in 1935 and obviously aimed at Nazi tyranny, he chronicles the story of John Calvin's vicious and petty-minded persecution of the liberal and tolerant theologian, Sebastian Castellio, who published a French translation of the Bible, much to Calvin's envious displeasure.

Under Calvin, mid-16th-century Geneva became a conformist theocracy, where virtue, as conceived by Calvin, became compulsory, and any deviation from which was regarded not merely as unconventional but as heretical and therefore punishable. Everyone had to say and do the same thing, under pain of excommunication. Of course, Calvin's zeal for virtue was a veneer for personal envy, ambition and resentment; Zweig shows us, with ever-contemporary relevance, how such zeal leads to terror and servitude.

The suppression of free speech in modern societies requires an immense apparatus of surveillance. An Australian journalist, Anna Funder, had the happy idea of recording the stories of East Germans a few years after the removal of the Berlin Wall. Her book is called Stasiland (Granta Books, 2003). With her aid, we learn what it is like to assume that everyone one meets is an informer, that every telephone is bugged, that every letter is opened, that every movement is watched. All this is necessary to prevent anyone from saying anything against the regime.

The very first story in the book demonstrates all the consequences of the suppression of free speech. A young girl in East Germany posts a few anti-regime sentiments in public, and from then on her life is haunted, well beyond the downfall of the German Democratic Republic. She is denied education and training, harried and imprisoned, as is her husband, who dies -- or is killed -- while incarcerated. The suppression of free speech thus has an ineluctable logic of its own.

These books should not induce complacency. We already censor our own opinions for a variety of reasons, and the recent episode in Denmark has demonstrated how easily we are intimidated. We ought to pay closer attention to those who have lost their freedom.

Theodore Dalrymple's most recent book is Our Culture, What's Left of It: The Mandarins and the Masses. He is a frequent contributor to publications such as City Journal and The Spectator.