Very few people can claim to have read and understood in its entirety Martin Heidegger's masterwork, Being and Time . And most of them are liars. The standard joke about Heidegger's extraordinarily convoluted language is that it is impossible to translate, even into German.

And yet it's no great exaggeration to say that pretty much any cultured person over the past 50 years has been touched by Heidegger's thought. If you've read any great postwar novel, or seen any play that follows on from Samuel Beckett's Waiting for Godot , or even enjoyed any of the movies or TV dramas that reflect their ideas at one remove, some bit of Heidegger has lodged in your brain. Which is awkward, because, as the publication for the first time of his philosophical notebooks now reveals, he was a thoroughgoing Nazi.

That Heidegger was a Nazi in a literal sense is not news: he joined the Nazi party in 1933 and remained a member until its dissolution, in 1945. Nor is it news that he behaved atrociously throughout the Hitler period. He took over as rector of Freiburg University in April 1933, after it had been "cleansed" of Jews, specifically in order to carry out the Gleichschaltung , or "bringing into line" of its teaching with that of the Hitler state.

He told students in November 1933 that “the Führer and he alone is the present and future German reality and its law”. He presided over a public book-burning. And he consistently minimised the Holocaust, categorising it as another of the distortions created by the modern technology he deplored.

So why is Heidegger’s Nazism even up for discussion? Because he had the extraordinary good luck to have an apparently unimpeachable advocate. Heidegger’s former student and lover Hannah Arendt was not just a brilliant and hugely influential thinker in her own right. She was also Jewish.

Arendt led the rehabilitation of her old professor’s reputation by arguing that his involvement in Nazism was not essential to his thought. It was an “escapade”. If it contained a moral, it was merely that great thinkers are unworldly creatures who should stay out of politics. Heidegger’s mistake resulted from the naive way in which he “succumbed to the temptation . . . to ‘intervene’ in the world of human affairs”. The active Nazi and the thinking philosopher were two entirely different people.

Arendt's rationalisations were always pretty weak, but they have gradually become untenable. The weight of evidence from scholars, such as Emmanuel Faye in Heidegger: The Introduction of Nazism i nto Philosophy , showed conclusively that the Nazism and the philosophy were utterly intertwined. Heidegger used his own seminars to make his ideas into tools of Nazi indoctrination.

But there was still one last redoubt. These seminars were from the period 1933 to 1935. It could still, just about, be maintained that he was then in the first flush of an enthusiasm that subsequently waned.

Now this last redoubt has fallen in the most shocking way. As part of the continuing official edition of his collected works, his estate has published Heidegger’s philosophical notebooks. These are not diaries; they are workings-out of his thought. The shock is that in this context, we find the great thinker denouncing the “rootlessness” and spirit of “empty rationality and calculability” of the Jews.

One of the greatest thinkers of the 20th century sounds indistinguishable from any other Nazi ideologue, whingeing about the power of the Jews and blaming them for the war. “World Jewry”, Heidegger writes in the notebooks, “is ungraspable everywhere and doesn’t need to get involved in military action while continuing to unfurl its influence, whereas we are left to sacrifice the best blood of the best of our people”.

He even seems to blame the Jews for the Nazi’s racial theories. He writes that the Jewish people, with their “talent for calculation”, were opposing Nazi theories while “they themselves have lived according to the race principle for longest”.

These are not casual remarks: Heidegger makes them in the context of his argument against democracy and modernity itself (which the Jews embody) and about “authentic” and “inauthentic” modes of being. (No prizes for guessing which category the Jews occupy.)

In the light of all of this, it is not just the case that admirers of Heidegger have a Nazi problem. It is also the case that much of western culture has a Heidegger problem. It is hard to overstate his cultural influence. Heidegger rethought metaphysics as radically as Einstein rethought physics. His basic ideas, for all the convolution of the way he teases then out, are simple. Consider the following propositions: that human beings are not isolated subjects but exist inextricably in a world; and that we exist in time and therefore our existence is shaped by moving inexorably towards death.

If these ideas seem obvious it is because Heidegger, who invented them, is everywhere in western culture: from Catch-22 to Breaking Bad . They can't be dumped, but they do have to be rethought in the knowledge that the great thinker who expounded them was also a moral idiot.

fotoole@irishtimes.com