In some ways this is also a very German book: long, earnest, plodding. Yet it is not really up to the exacting standards of German scholarship (or of English narrative sparkle), relying, as it does, largely on other scholars’ accounts of the great thinkers in question, and quoting the secondary sources far more than the original works of “genius.” Too often Watson urges us to revere people or books “now recognized,” “widely viewed” or “generally regarded” as brilliant. Readers may grow weary of being told what to think.

In effect, Watson has given us a kind of Dictionary of German Biography, along with a great deal of name-dropping. There were many German geniuses. But what was “the German genius”? To understand what was special about Germany, we need to know more than Watson tells us about the world that produced these thinkers. He does offer some valuable hints, insisting, for example, on the importanceof the 17th- and 18th-century religious revival known as Pietism, which urged believers to devote themselves to improving life on earth. Certainly he is right to emphasize Germany’s Protestant heritage (and the many preachers’ sons who populate his pages), but secularized Protestantism shaped other lands as well — notably Britain, where Catholics and Jews played smaller roles than in Germany.

More helpful is his emphasis on the role of universities in creating new knowledge and a new class defined by education. At Göttingen and Halle in the 18th century, and at Berlin and Bonn in the 19th, Germany invented the modern university, combining teaching with research in both humanities and science — at a time when Harvard and Oxford were conservative and theology-centered. University grads staffed a new bureaucracy of experts, and their work in laboratories and archives made research “a rival form of authority in the world.” The universities also enshrined a new ideal of individual cultivation (the fetishized German word is “Bildung”). Germans from Kant to Mann embraced this “secular form of Pietism,” turning inward to find truths not anchored in reason or revelation — and often, like Mann in 1915, choosing mystical wholeness over messy liberal politics.

This is modern subjective individuality, as expounded by philosophers like Martin Heidegger. Even if Heidegger hadn’t been a Nazi, we would still face the question of whether Hitler was the nemesis or the culmination of German genius. Just as Mann had to acknowledge Goebbels as his bastard child, Watson knows that Germany cannot disown the Nazis. He borrows many different and contradictory theories of the German catastrophe, variously suggesting that the educated middle class was too weak to stop Hitler, that it abdicated its responsibility to do so and that its antipolitical ideals taught a nation to welcome a charlatan’s promises of a redemptive community.

Yet no history of ideas can explain the tragedy of German genius. Hitler may have fancied himself a great thinker, but his success came from his brilliance as a political tactician in a troubled time. Intellectuals admired (or feared) him for his ability to seduce millions of voters who knew nothing of Kant or Heidegger. Watson gives us a compilation of German ideas; a history of the German genius would be a different and dicier matter.

Watson’s chapters on the anguish of postwar German intellectuals remind us that he is a world away from the ­mystical nonsense of his countryman Houston Stewart Chamberlain. Nonetheless, his attempt to exalt a national character suggests that he is offering something not altogether different for our chastened time.