If I had to rate the best intellectual experiences of my life, choosing the two or three most profound—a tendentious task, but there you are—one of them would be reading Heidegger. I was in my late twenties, and struggling with a dissertation on the nature of consciousness (what it is, where it comes from, how it fits into the material world). This had turned out to be an impossible subject. Everything I read succeeded only by narrowing the world, imagining it to be either a material or a spiritual place—never both.

Then, in the course of a year, I read Heidegger’s 1927 masterwork, “Being and Time,” along with “The Essence of Truth,” a book based on a series of lectures that Heidegger gave in 1932. It was as if, having been trapped on the ground floor of a building, I had found an express elevator to the roof, from which I could see the stars. Heidegger had developed his own way of describing the nature of human existence. It wasn’t religious, and it wasn’t scientific; it got its arms around everything, from rocks to the soul. Instead of subjects and objects, Heidegger wanted to talk about “beings.” The world, he argued, is full of beings—numbers, oceans, mountains, animals—but human beings are the only ones who care about what it means to be themselves. (A human being, he writes, is the “entity which in its Being has this very Being as an issue.”) This gives us depth. Mountains might outlast us, but they can’t out-be us. For Heidegger, human being was an activity, with its own unique qualities, for which he had invented names: thrownness, fallenness, projection. These words, for him, captured the way that we try, amidst the flow of time, to “take a stand” on what it means to exist. (Thus the title: “Being and Time.”)

In “The Essence of Truth,” meanwhile, Heidegger proposed a different and, to my mind, a more realistic idea of truth than any I’d encountered before. He believed that, before you could know the truth about things, you had to care about them. Caring comes first, because it’s caring about things that “unconceals” them in your day-to-day life, so that they can be known about. If you don’t care about things, they stay “hidden”—and, because there are limits to our care, to be alive is “to be surrounded by the hidden.” (A century’s worth of intellectual history has flowed from this insight: that caring and not caring about things has a history, and that this history shapes our thinking.) This is a humble way to think about truth. It acknowledges that, while we claim to “know” about a lot of things intellectually, we usually seek and know the deeper truth about only a few. Put another way: truth is as much about what we allow ourselves to experience as it is about what we know.

When I read Heidegger’s books, I “knew”—but didn’t particularly care—that he had been a Nazi. (He joined the party in 1933, the year after giving the lectures behind “The Essence of Truth.”) I was so fascinated by his philosophy that his Nazism stayed “hidden”; though his ideas felt vivid and present, his biography belonged to the past. But, over the past few months, not caring has become more difficult. That’s largely because of a philosophy professor named Peter Trawny, who has begun publishing some of Heidegger’s anti-Semitic writings. Trawny is the director of the Martin Heidegger Institute at the University of Wuppertal, in Germany, and the editor of Heidegger’s “black notebooks,” some of which were published for the first time this spring. (Heidegger wrote in the small, black-covered notebooks for nearly forty years—publishing them all could take decades.)

It’s always been safe to assume that Heidegger, being a Nazi, was also an anti-Semite (though not necessarily a “virulent” one, whatever that term might mean). But, as my colleague Richard Brody wrote a few weeks ago, the passages reveal a particularly unsettling kind of anti-Semitism—one which hasn’t been fully visible before. They show that, even as Heidegger held the most banal and ignorant anti-Semitic beliefs (he wrote about a worldwide conspiracy of “calculating” Jews “unfurl[ing] its influence”), he also tried to formulate a special, philosophical, and even Heideggerian kind of anti-Semitism. (Jews, he writes, are “uprooted from Being-in-the World”—that is, incapable of authentically caring and knowing.) The passages, some of which were written during the Second World War, account for only a few pages out of more than a thousand. But they have alarmed and disgusted Heideggerians because they show that Heidegger himself had no trouble using his own philosophy for anti-Semitic ends. Philosophy has a math-like quality: it’s not just a vocabulary, but a system. A failure in one part of the system can suggest a failure everywhere. And so, earlier this year, in a book called “Heidegger and the Myth of Jewish World Conspiracy,” Trawny asked the inevitable question: could Heidegger’s philosophy as a whole be “contaminated” by Nazism?

When Trawny came to New York, during the second week of April, for a panel on Heidegger and Nazism hosted by the Goethe Institute, in the East Village, all sorts of Heideggerians, from the casual to the committed, came to hear him speak. The general rule seemed to be that the more time you’d spent thinking about Heidegger, the more unnerved you were by the controversy. Relaxed, curious undergrads gathered near the sunlit windows at the back of the audience. (One couple had their arms around each other, apparently on a date.) Further up, the grad students, in their too-old or too-young outfits, looked alert and inquisitive: for them, this was an issue of professional interest. A few rows on, an explosion of gray marked where the older professors huddled together. And at the front sat the panelists: Trawny, along with two American professors of philosophy, Roger Berkowitz and Babette Babich, from Bard and Fordham, respectively. Outside, it was spring. Inside, it was dim, airless, and funereal.

Because Trawny was from Germany, no one knew what he would be like in person—an incomprehensible hermeneutist? A cool judge of history? He turned out to be a tall, disarming man of fifty who sounded less like a judge than a disappointed lover. In a soft German accent, he explained what it had been like to read the notebooks for the first time. “Of course, you have passages about Hölderlin, about Nietzsche, about Bolshevism,” he said—the usual Heideggerian subjects. “But then, suddenly, a passage about the Jews.… You think, Okay, whatever.… And then suddenly you have the second, and you have the third, and you have the fourth, and you have the sixth, and you think, What the hell! Why is he doing this?” As a lifelong Heideggerian, reading and publishing these passages had been “very painful,” Trawny said; it had also introduced all sorts of practical complications into his life. “I’m the director of the Martin Heidegger Institute, and I actually want to be that for a longer time,” he said, to laughter from the audience. (“You cannot be the director of the Adolf Hitler Institute,” a colleague had warned him.) He went on, “If we would say that Heidegger really was an anti-Semitic philosopher, then, yeah, that would be really a catastrophe, in a certain way, for me.” This was true, to varying degrees, for many in the room. It was good to hear someone admit that the controversy wasn’t a matter of purely intellectual interest.