“Back from Syracuse?” That was how Heidegger’s colleague greeted him when he returned to teach after the postwar government barred him from the profession for collaborating with the Nazi regime. Heidegger had, like Plato to the tyrant Dionysius of Syracuse, sought to “lead the leader.” He had set himself up to be Nazism’s philosophical preceptor. Shortly after the Nazis seized power, he maneuvered to become rector of the University of Freiburg. He carefully stage-managed his inaugural address. Flanked by SA and SS members, he outlined his view of nazified university life; then the whole room sang the Horst-Wessel-Lied, the anthem of National Socialism.

Later, Heidegger claimed that he had only been loyal to Nazism for a few months, having stumbled innocently into “error,” before he turned into a regime critic. His followers have uncritically repeated that line even in the face of mounting evidence, but the historical record cannot be dismissed.

The start of the publication of the Black Notebooks, a series of volumes that Heidegger compiled between 1930 and 1970, in 2014 made it impossible for his defenders to ignore his more unsavory opinions. Two recent books, Richard Wolin’s Heidegger in Ruins and Guillaume Payen’s Martin Heidegger’s Changing Destinies, draw on the discoveries of the notebooks to examine the extent of Heidegger’s reactionary views. Together, they make an incontrovertible case that there was nothing naive in his support for Adolf Hitler — his outlook reflects a clear and deep-seated commitment to the worldview of Nazism.

Between 1929 and 1930, Heidegger took what he described as a philosophical Kehre (turn), shifting focus to an examination of Dasein, a word comfortably translated as “existence” but which Heidegger uses to denote the mode of experiencing reality available to human beings who assume a familiarity and concern for the social world. Through this notion, Payen argues, Heidegger treats a volkish outlook as the natural mode of relating to the world. Payen thus writes that Being and Time, published in 1927, “turned out to be an upscale Blut und Boden [blood and soil] work.”

Wolin, who proceeds somewhat more thematically than Payen, shows the numerous close links between Heidegger’s philosophy and politics. Heidegger believed that Germans were “the most metaphysical of peoples” because they were uniquely rooted in their soil (Bodenständigkeit). This meant that they were fated to reconnect history with Being — he thus believed in the Nazi “New Awakening” with “inner conviction.” In the Notebooks, he praised Nazism as a “barbaric principle.” “Therein lies its essence and its capacity for greatness” — he worried only that it might “be rendered innocuous via sermons about the True, the Good, and the Beautiful” — metaphysical concepts that Heidegger sought to overturn in favor of his more grounded notion of Being. Solely by “complete and total devastation” could Germany “shatter the 2,000-year reign of metaphysics.” He referred to the Jews as “rootless” because of their supposedly “cosmopolitan” and “nomadic” racial nature; it threatened, he believed, the German Volk’s destiny.

The Spanish poet and philosopher George Santayana called T. S. Eliot’s ideas “subterranean without being profound” — the very same could be said of Heidegger’s. Rejecting universal history in favor of “primordial myth,” he believed that “rootedness-in-soil” (Bodenständigkeit) constituted “subterranean” knowledge. Germany, by reconnecting with its tribal Teutonic origin, could lead Europe toward a “new Beginning;” rekindling Greek glory — the linkage of Germany with Sparta was a mainstay of Nazi cliché. This “new Beginning” required a new philosophy — supplied by Heidegger himself, naturally — that encouraged struggle and “veneration of a Volk for the sake of hardness.” Accordingly, he believed in the redemptive power of Nazi violence: it served as a counterforce to Enlightenment “nihilism.” The Nazi movement could thus put an end to centuries of Seinsvergessenheit (forgetting of Being).

No one can now claim that Heidegger wasn’t enthusiastically pro-Hitler; to get a measure of the remaining controversies, look to where Wolin and Payen disagree. Wolin believes Heidegger endorsed the final solution in 1933; Payen is skeptical. By 1929, Heidegger had become obsessed with the “Jewification of the German spirit.” He thought that Chancellor Franz von Papen was controlled by Jewish capital and saw Hitler as a bulwark against “Judeo-Bolshevism.” It would be worth inquiring, he said, into “world Jewry’s predisposition toward planetary criminality.” Such was his state of mind when he called for the “total annihilation” of Jewishness.

The domestic enemy can attach itself to the innermost roots of the Dasein of a Volk; it can set itself against the Volk’s own essence and act against it. The Kampf is all the more fierce and all the more difficult . . . since it consists in a mutual coming to blows. It is often far more difficult and wearisome to catch sight of the [domestic] enemy as such, to bring the enemy into the open, to harbor no illusions about the enemy, to keep oneself ready for attack, to cultivate and intensify a constant readiness, and to prepare the attack, looking far ahead with the goal of total annihilation [völlige Vernichtung].

Wolin takes this to be a straight endorsement of the kind of genocidal program sanctioned by the Wannsee Conference. Payen, however, thinks that we should read this comment in light of a petition by the German student body to burn Jewish books. He thus believes that Heidegger merely spoke of cultural destruction, not genocide — nazifying the university and purging Jewish professors. That’s the most lenient possible interpretation, but it is hardly exculpatory. Heidegger’s rhetoric provided a rationale for genocide. Killing thought, in effect, meant killing the thinker. They were condemned not for what they wrote but for who they were, and Heidegger knew it. As Joseph Roth said, “They will burn our books and mean us.”

The Black Notebooks have eroded one of the last excuses defenders of Heidegger had. It used to be said, even by critics, that Heidegger opposed Nazi biological racism; by contrast, Heidegger thought of race in “spiritual” terms. But even that can no longer be maintained, as Wolin expertly shows. Heidegger believed in the “Nordic race” theory; he justified the Nazi euthanasia program; he invited the psychiatrist Heinz Riedel to lecture on “problems of the Rassenfrage [race question]” and Helmut Haubold of the SS was likewise invited to lecture on eugenics; and he lobbied to have the University of Freiburg purchase Ludwig Schemann’s papers on the scientific racism of the French aristocrat Arthur de Gobineau, reasoning that it would facilitate “race science” studies. When he criticized reductive “biologism,” he wasn’t saying that there were no biological races; rather, he was saying that there was more to race than biology. He simply opposed one Nazi race theory in favor of his own Nazi race theory.

In fact, Nazi race ideology was never based solely on biological claims. Numerous Nazi thinkers were open to spiritual views of race. Thus, the legal theorist Karl Larenz praised the Nazi “race mystic” synthesis of “blood” and “spirit.” Nazism had occult, irrational roots; they called their movement “idealist” in opposition to science and Marxist materialism. Heinrich Himmler, let’s remember, believed in the Cosmic Ice Theory, which held that an intergalactic clash between “ice planets” and “fire planets” could explain the disappearance of Atlantis. Alfred Rosenberg’s The Myth of the Twentieth Century explicitly praised irrationalism — it propounded a “spiritual” view of race that rejected science because it sought to “reduce blood to a chemical formula.” Heidegger could have signed on to that statement.

One can learn much from reading habits: in the morning, even before Hitler became chancellor, Heidegger would read the Nazi Völkischer Beobachter or the ultrareactionary Die Tat; in the evening, he would curl up in bed with some fascist tract. Ernst Jünger inspired him greatly, and he praised Hans Grimm’s Lebensraum novel Volk ohne Raum for its presentation of “the fate of our Volk.” By 1931, he had read Mein Kampf, recommending it heartily. He especially liked Werner Beumelburg’s revanchist Deutschland in Ketten. It “clear-sightedly” explained the “humiliation” of Germany; “it was open season on German women and girls,” Beumelburg lamented, because there were French colonial troops in the occupied Ruhr. Heidegger greeted the Reichstag Fire Decree, suspending civil liberties, with euphoria — he swiftly sent a copy of the hagiographic Hermann Göring: A Portrait of a Life to a friend.

What caused Heidegger to side with the Nazis? Payen places much emphasis on Heidegger’s fanatical wife Elfride, but also cites his experience in the First World War, which converted him to the cult of heroic violence. By the end of the war, he had become convinced that Germany needed a revolution from the Right that would usher in a new national spirit. His fascist imagination was further shaped by Friedrich Nietzsche and Heraclitus, whose epigram “War is the father of all things” he revered. His shift from Catholicism to Nazism was eased by his contempt for socialists and Jews.

Like Hitler, he never tired of pointing out that National Socialism, whatever compliments it paid “the worker,” had no connection with Marxist thought. But if Heidegger’s political and ethnic prejudices made him susceptible to Nazism, it was really his philosophical convictions that mattered most. It wasn’t merely what he believed but how he believed it; over time, he became increasingly vatic, increasingly irrational.

Wolin stresses that Heidegger’s critique of Western rationality was no ordinary skepticism but the full rejection of reason itself. The idea of validity, Heidegger claimed, issued into “confusion, perplexity, and dogmatism.” It was time, he said, to “put an end to philosophizing,” because philosophy was nothing but the “history of error.” Instead, Germany should turn to the “metapolitics of the historical Volk.” He thus replaced reason with blood mythology. “Truth,” he wrote, “is not for everyone, but only for the strong.” If he sounded esoteric, it was because truth emanated from a sphere beyond the rational; “Making itself intelligible is suicide for philosophy.” He wrote that “mysteriousness constitutes the authenticity and greatness of historical knowledge.” And he excoriated what he called “the dictatorship of the comprehensible.”

Quite knowingly, Heidegger nurtured a coterie of loyal students who treated his every sentence as oracular truth — he gave up on critical thought, instead channeling the “sendings of Being.” It felt, one student said, like a “rendezvous with destiny.” Even highly inquisitive followers fell for his charisma. Hannah Arendt eventually concluded that he had sunk into superstition, but she too felt the siren call: he taught them, she said, to “think passionately.” Heidegger thought that he had a mission to reconnect the German spirit with pure barbarity. He remained unrepentant; in the end, his critique of the Nazi regime was simply that it had failed the Nazi movement — it hadn’t ushered in a “new Beginning.”