The French writer and philosopher, Bernard-Henri Lévy, has long functioned as a kind of ambassador-at-large for the causes of peoples from, among other far-flung locales, Sarajevo, Darfur, Dhaka, Erbil, and Kyiv. His new book, “Israel Alone,” confirms him as a passionate defender of the Jewish state. Mr. Lévy is no stranger to the cause of Zion, and his uplifting of Israel’s war as righteous is welcome in the midst of a year of calumny.

“Israel Alone” is, among other virtues, a slim volume. More of a dispatch than a disquisition, it was released in French in March. Mr. Lévy relates that he “arrived in Israel the morning after October 7” when “Tel Aviv and Jerusalem seemed like dead cities.” He invokes the “barbarians coming out of nowhere; the breathless, silent savagery.” He discerns in October 7 “an event whose shockwaves and blast effect” would change the world. 

Mr. Lévy calls Hamas’s attacks a “hostage taking without precedent since the rape of the Sabine women by Romulus’s Romans,” a mythical event from the dawn of the history of the Eternal City. He gives October 7 a history by noting the “eternal propensity of democracies, when faced with unthinkable barbarity, to know without believing, to possess the data without drawing conclusions.” Savagery is most visible when it hides in plain sight.

The Frenchman is particularly persuasive when he describes the aftershocks of October 7 in the Fifth Republic. He calls it a “terrible moral debacle to cede the country of Chrétien de Troyes, Rashi, Racine, and Marcel Proust to illiterates.” He cites the philosopher Emmanuel Levinas, who warned of an “‘an icy wind’ blowing through the rooms of well-to-do Jews in Paris and Berlin” and of the “small splendors” of the Jews ransacked by mobs. 

While Mr. Lévy reckons that even the depredations of October 7 did not put the Jewish state in mortal danger, he invokes another “geography, that of dreams, fears, and imagination.” In this dimension, “October 7 marks the alignment, for the worse, of Israel with the diaspora.” He calls this new vulnerability the “revenge of Amalek, of the oldest enemy of the Jewish people.” That old foe has “come out of limbo to bang on our doors and drum in our ears.”

“Israel Alone” works to convince the world that the attacks on Nahal Oz, Be’eri, and other communities were not only a “monstrous pogrom that sent Jewish memory back eighty years” but also “another crack in the fragile veneer of civilization.” For a moment, but only for a moment, the “world was gripped by a brutal, ravaging, stunning fear” of a barbarism unbound. Such empathy, though, was short-lived.

Mr. Lévy embeds his account of the October 7 assaults within a broader portrait of a free world threatened by rapacious autocrats. He calls President Putin the “KGB man of a thousand ruses” and a “postmodern Mad Max who has replaced the motorcycles of the apocalypse with tanks and hypersonic missiles.” He calls Hamas the “sword and toy of a counter-empire.” Israel is “not a pawn, but a point” in a world swimming in savagery.

The style of “Israel Alone” — loose and free associative — will leave some readers adrift in Mr. Lévy’s stream of consciousness. His frank love for the Jewish state and his championing of a “radiant, luminous, exemplary Zionism,” though, amount to sturdy and welcome bedrock beliefs. His passion for “this little world of people stranded on the tiny strip of land” discloses that this  Jacques Lacan-quoting intellectual feels Jerusalem in his kishkes.