On 16 November 1980, Louis Althusser strangled his wife at the elite École Normale Supérieure in Paris. The Marxist philosopher was never arrested for the crime but instead spent four years at the Sainte-Anne hospital. Why? According to Israeli historian Shlomo Sand, such was French deference to its intellectuals that the establishment, including the justice minister and ENS alumnus Alain Peyrefitte, ignored the law. The supposition was simply not allowed “that a philosopher of Althusser’s status could have deliberately committed a murder; so he had to be automatically considered mentally unbalanced”.

Twenty years earlier, Jean-Paul Sartre benefited from similar attitudes. In 1960, the existentialist called on French soldiers to refuse to fight in Algeria’s war of independence. In response to those demanding Sartre’s prosecution, President de Gaulle said: “You do not arrest Voltaire.”

For those of us who live on the other side of the Channel, French regard for intellectuals is puzzling. If, say, Germaine Greer had strangled her partner, or Richard Dawkins had incited fellow atheists to burn mosques and churches, you would suspect, they would be detained at Her Majesty’s pleasure, albeit with fat advances for their prison memoirs. Why the difference? Sand suggests anglophone anti-intellectualism is Protestantism’s legacy: since we got rid of Catholicism’s clerical hierarchy, we’ve been loth to replicate that authority with its secular counterpart. France’s intellectuals, by contrast, “have inherited both the role of the court jester, able to say whatever was in their minds without being punished, and of the priest, serving as intermediary between the believer and divine truth”.

Sand starts his history with the Dreyfus affair and ends it, nauseated, in 2015, as the French establishment marches in solidarity with murdered workers at Muslim-baiting magazine Charlie Hebdo and there are calls for Michel Houellebecq to be inducted into the Académie Française for his novel Submission (one that imagines France busted down to a mere province of a Mediterranean caliphate). “The modern Parisian intellectual was born in the battle against Judeophobia, the twilight of the intellectual in the early 21st century is happening under the sign of a rise in Islamophobia,” Sand argues.

Though many books have been written about the decline of the French intellectual, Sand’s is a welcome addition since it is written, not by a navel-gazing insider, but by someone by turns seduced and revolted by that Gallic neologism, les intellocrates. Now a professor of history in Tel Aviv, Sand started his working life making radio sets in Israel before studying in France and his blue-collar past haunts his thinking. His early scholarly work was on French syndicalist Georges Sorel, for whom workplace self-organisation was key to socialist revolution. Sand inherits his doubts that workers need to be led to communist paradise by soft-handed Left Bank scribblers.

Romantic levity … Simone de Beauvoir

and Jean-Paul Sartre in 1967. Photograph: Sipa Press/Rex Features

But first, when Sand read Albert Camus, Sartre and Simone de Beauvoir, he was seduced. “I was bowled over by the romantic levity of those who lived from writing, by the idealisation of this intellectual commitment in the service of just causes, and against the enchanting backdrop of the City of Light.”

Later, he was revolted. He came to believe that De Beauvoir and Sartre’s pro-Jewish posturing after the war was born of bad conscience for doing nothing effective to fight nazism or help Jews. Indeed, during the Nazi occupation, De Beauvoir signed a form denying she was a Jew in order to keep teaching at a lycée, while both she and Sartre neglected their former lover, Bianca Lamblin, a Polish Jew who holed up from the Gestapo in the south of France for the duration of the war. Sand snarls: “The ardent discussions on authenticity and existentialism in the cafes of Saint-Germain-des-Prés left them no time to take an interest in the existential experience of their abandoned and persecuted lover, whose grandfather and aunt were murdered in the camps.”

De Beauvoir’s Jewish lover Claude Lanzmann, too, gets indicted for his 1985 documentary Shoah. The film invites you to believe, Sand argues, “that the persecution of Jews (and of Jews alone) only took place east of the Rhine, and particularly in Poland, a country so ‘unintellectual’ and ‘antisemitic’”. The Jews interned by the French authorities at Drancy on their way to Auschwitz did not figure in Lanzmann’s portrait of the Holocaust, one that, for Sand at least, “so well agreed with the image that Parisian literati wanted to give of themselves”.

Michel Houellebecq … he clings to a France that is ‘totally imaginary’. Photograph: Miguel Medina/AFP/Getty Images

What Sand’s book lacks, despite its refreshing absence of deference, is a sense of what made French intellectual production since the war so compelling. Lévi-Strauss, Barthes, Kristeva, Lacan, Derrida, Cixous, Deleuze and Guattari are scarcely mentioned and Foucault only gets a cameo. The Maoist philosopher Alain Badiou once told me that, while British postwar philosophy has its “côté somnifère” (its soporific aspect), French intellectual life in the same period has been a wild adventure. I’d like to read that adventure story, but Sand doesn’t tell it.

Instead, he explores the embarrassing truth that, while in the new millennium the quality of French intellectual life has plummeted, its reputation remains. He bracingly compares media-friendly intellectuals such as Houellebecq, Éric Zemmour and Alain Finkielkraut to Nazi-collaborating writers such as Robert Brasillach and Pierre Drieu La Rochelle. Like such past figures, Sand argues, they cling to a France that is “totally imaginary” and yearn for it to be purified of the Other. In 1940 that meant Jews, in 2018 Islam.

For Finkielkraut, author of The Unhappy Identity, the collapse of France’s educational system and high culture explain his homeland’s decline: “We no longer teach that the colonial project also sought to educate, to bring civilisation to savages,” he wrote. For Zemmour, author of The French Suicide, the problem is France has become too feminised, hedonistic and individualistic. For both, as for Houellebecq, into France’s decadent vacuum steps the scary Other in the form of the racist projection of their own fears – the macho, barbaric Islamist bent on destroying everything French intellectuals, ostensibly, have held dear.

Perhaps it takes an outsider Jew to diagnose the sickness of French intellectual life. Near the end of the book, Sand looks at a cartoon of Muhammad published in Charlie Hebdo, “a cruel-looking bearded figure wrapped in a white jellaba, his eyes hidden and holding a long pointed knife”. He has seen that image before. Where? In the Jew-hating cartoons published in the 1890s in La Libre Parole to whip up antisemitic sentiment during the Dreyfus affair. “It is surprising to see how much the ‘Semitic’ Jews of the past resemble the ‘Semitic’ Muslims of today: the same ugly face and the same long and fat nose.”

No wonder, then, that when some 4 million French people joined the march for Charlie Hebdo’s murdered court jesters three years ago, Sand was not one of them. He is not the kind of guy to sport a “Je suis Charlie” badge – his admiration for French intellectuals, such as it is, does not extend to self-identifying with Islamophobes.