It takes a strong philosopher to assume control of a preposition and propel it into a foreign language. That is what Friedrich Nietzsche did with the word über. In German, it can mean “over,” “beyond,” or “about.” You are reading an essay über Nietzsche. As a prefix, über is sometimes equivalent to the English “super”—übernatürlich is “supernatural”—but it has less of an aggrandizing effect. Nietzsche altered the destiny of the word when, in the eighteen-eighties, he began speaking of the Übermensch, which has been translated as “superman,” “superhuman,” and “overman.” Scholars still debate what Nietzsche had in mind. A physically stronger being? A spiritual aristocrat? A kind of cyborg? “Overperson” might be the most literal equivalent in English, although it is unlikely that DC Comics would have sold many comic books using that title.

In 1903, three years after Nietzsche’s death, George Bernard Shaw published his play “Man and Superman,” in which he equated the Übermensch with an overflowing “Life Force.” Three decades later, Jerry Siegel and Joe Shuster, two Cleveland teen-agers, created the first “Super-Man” story, depicting the character not as a caped hero but as a bald, telepathic villain bent on “total annihilation.” Super-Man soon reëmerged as a muscle-bound defender of the good, and during the Second World War he jumped into the fight against the Nazis. It’s unclear whether Siegel and Shuster knew of Nietzsche in 1933, but the word “superman” hardly existed in English before the philosopher’s ideas began to spread.

As Nietzsche worked his wiles on generations of English-speaking college students, the word Übermensch increasingly stood on its own, and “über” slipped into English as a prefix. In the nineteen-eighties, Spy described the Hollywood agent Michael Ovitz as an “über-agent.” The umlaut-free car-sharing service Uber, originally known as UberCab, is a related development, hinting at Silicon Valley fantasies of world domination. In the late twentieth century, the word “super” rebounded into German as all-purpose slang for “very”; if you wish to describe something as really, really cool, you say that it is super super toll. Somewhere, Nietzsche is laughing hysterically while screaming in anguish.

The adventures of “super” and “über” are a case study in the inescapability of Nietzsche’s philosophy, which has affected everyday discourse and modern political reality like no body of thought before it. Countless books on Nietzsche are published in dozens of languages each year, linking him to every imaginable zone of life and culture. One can read about the French Nietzsche, the American Nietzsche, the pragmatic Nietzsche, the analytic Nietzsche, the feminist Nietzsche, the gay Nietzsche, the black Nietzsche, the environmentalist Nietzsche. Lurking amid the crowd of avatars is the proto-fascist Nietzsche—the proponent of pitilessness, hardness, and the will to power who is cited approvingly by such far-right gurus as Alain de Benoist, Richard Spencer, and Aleksandr Dugin. Can a philosopher who has sown such confusion be said to possess a coherent identity? Or, as Bertrand Russell once argued, is Nietzsche merely a literary phenomenon?

When I was in college, in the nineteen-eighties, the French Nietzsche held sway. It was the heyday of post-structuralism, and Nietzsche appeared to anticipate one of the central insights of that era: that we are at the mercy of ever-shifting systems and perspectives. The work of Michel Foucault, Gilles Deleuze, and Jacques Derrida is all but inconceivable without Nietzsche’s example. So many professors distributed photocopies of the 1873 essay “On Truth and Lie in an Extra-Moral Sense” that we could have recited it as a postmodern pledge of allegiance: “What, then, is truth? A mobile army of metaphors, metonyms, and anthropomorphisms. . . . Truths are illusions about which one has forgotten that this is what they are.”

In the past few decades, other Nietzsches have come to the fore. Anglo-American philosophers have aligned him with various schools of post-analytic thought, seeing him as an idiosyncratic kind of psychologist or sociologist. Nietzsche’s political thinking is also a trending topic, although his ideas are devilishly difficult to reconcile with modern conceptions of left and right. He raged against democracy and egalitarianism, but also against nationalism and anti-Semitism. Nietzsche is often quoted in the chat rooms of the far right, and he also surfaces regularly in leftist discussions about the future of democracy.

Walter Kaufmann, the German-American émigré whose translations of Nietzsche were long the standard versions in English, once declared that the philosopher’s writings are “easier to read but harder to understand than those of almost any other thinker.” Ideologues keep trying to appropriate him because they want his rhetorical firepower on their side. Yet Nietzsche, like his fallen idol Richard Wagner, is at once emphatic and ambiguous, overbearing and elusive. Nietzsche’s famous adage that there are “no facts, only interpretations” is among his more debatable propositions, but it applies perfectly well to his own infuriating, invigorating body of work.

The itinerant, solitary, sickly life of Nietzsche has been told many times, most recently in English by the biographer Sue Prideaux, in “I Am Dynamite!” The title comes from an unnerving passage in “Ecce Homo,” Nietzsche’s autobiographical book of 1888, which was completed a couple of months before he descended into insanity, at the age of forty-four:

I know my lot. One day my name will be linked to the memory of something monstrous [etwas Ungeheueres]—to a crisis like none there has been on earth, to the most profound collision of conscience, to a verdict invoked against everything that until then had been believed, demanded, held sacred. I am no man, I am dynamite.

How a Lutheran pastor’s son, trained in classical philology, ended up on that precipice of brilliance and madness is the essential drama of Nietzsche’s life. The passage has been read as an eerie premonition of his future appropriation by the Nazis—although there is no way of knowing exactly what kind of crisis is meant. Ungeheuer is an ambiguous word, hovering between the monstrous and the gigantic. Kaufmann translated it as “tremendous,” which takes away too much of the ominousness. Here is the sumptuous difficulty of Nietzsche: when you drill down on a word, an abyss of interpretation opens.

Nietzsche grew up in the village of Röcken, outside Leipzig. The church where his father preached still stands; Nietzsche, the scourge of Christianity, is buried in a plot next to the building. The elder Nietzsche, like his son, was afflicted by severe physical and mental problems—violent headaches, epileptic strokes, amnesiac episodes—and died at the age of thirty-five, when Friedrich was four. Nietzsche himself had a mental breakdown in middle age. The old story that his breakdown stemmed from syphilis is now widely doubted; a likelier explanation is a hereditary neurological or vascular disorder. Neurologists in Belgium and Switzerland have concluded that he had cadasil, a genetic condition that causes repeated strokes.