Martin Heidegger: The philosopher embraced Nazism yet was rehabilitated after the war

Perhaps only if one is under mortal terror can one understand why highly civilised people endorse extreme dictatorships. One thinks of the fear in which Stalin forced Shostakovich to live; or the obedience that Furtwängler and Richard Strauss chose to show to the Nazi regime. Yet how does one explain why civilised people who not merely have the capacity for thought, but whose life is thinking, embrace evil? In her new book Hitler's Philosophers (Yale, £25) Yvonne Sherratt explores, among other things, this conundrum. She does not merely look at those who, literally, should have known better but who threw themselves and their learning behind the Nazis. She also looks at those, mainly but not exclusively Jewish, who maintained a sense of intellectual and moral integrity and took against Hitler, and shows what happened to them. It is, in the end, a peculiarly unedifying story, though exceptionally well told.

The industry that portrays and describes the Third Reich is now considerable, with many authors and publishers regarding the subject as inexhaustible. This aspect of Hitler's terror — how he sought to control the thought processes first of academia and then, presumably, of the rest of Germany who would defer to the eminent philosophers in the Reich's universities — has been insufficiently explored.

Dr Sherratt describes the influences on Hitler before he rose to power — notably Houston Stewart Chamberlain, from the Wagner family circle in Bayreuth, Feuerbach, Schopenhauer and (insofar as he could understand him) Nietzsche. Hitler does not really seem to have understood philosophy. Had he done so he would have recognised Chamberlain as a charlatan and seen that his reading of Nietzsche was superficial and selective. This leads inevitably to the main problem with Hitler: of all "his" philosophers, he was the philosopher-in-chief. Since his principal tract was the ragbag of prolix bigotries that is Mein Kampf, we know how warped and inadequate the quality of his "thought" was, and how little qualified he was to judge others.

Dr Sherratt provides compelling studies of the philosophers who fled or died rather than play along with Hitler. There was Walter Benjamin, a philosopher who was supposedly the finest writer in German, who went into exile shortly after Hitler came to power. It was his misfortune to have made France his home, and as the Gestapo closed in on him near the Spanish border in September 1940 he took enough morphine "to kill a horse". There was Theodore Adorno, a musicologist who went first to Oxford (where he was taken up by Maurice Bowra, but patronised and derided by Isaiah Berlin, in further proof that his judgment and humanity were not all his adorers claim them to have been) and then to America. He ended up in Los Angeles, immersed in Hollywood. There was also Hannah Arendt, brilliant student and sometime mistress of Martin Heidegger, who managed to escape round-ups in an almost miraculous fashion. And it is Arendt who brings us back to the most puzzling and disturbing feature of this story.