One of the things that make Eichmann in Jerusalem a distinctively Arendtian work, and not simply a piece of journalism, is the close analysis of the philosophy of Immanuel Kant at the midpoint of the book. Immanuel Kant was a philosopher during the German Enlightenment, who, in his Groundwork of the Metaphysics of Morals in 1785, argued that the only basis for true moral action is what he refers to as the "categorical imperative," that is, acting in such a way that one's actions could form the basis of a universal law. This philosophical concept is invoked by Eichmann, who claims, rather absurdly, that he had always lived his life according to the categorical imperative.
Rather than dismiss this claim, Arendt chooses to take it seriously. From the mid-1940s up through the 1960s, Kant had largely fallen out of favor among the politically-engaged philosophers of Germany. Indeed, Nazism had called the entire canon of German thought into question: if philosophy, music, and literature were supposed to lift up and enlighten, then why had they failed so spectacularly? In their book Dialectic of Enlightenment in 1946, the philosophers Theodor Adorno and Max Horkheimer argued that Kant's emphases on rationality, order, systematic thinking, the suppression of feeling, and obedience to the law already contained within them the roots of fascism. For Kant, it is simply the way a moral action is formulated, and not its actual substance or consequences, that makes it moral. In that way, Adorno and Horkheimer argued, the icy rationalism of his thought led to the iron-clad logic of fascism, which determined that the highest good was to obey the Führer. For many thinkers of that generation, Kant was associated with an attitude of submission; the 1960s, in particular, saw a philosophical search for alternate philosophical figures of revolution and liberation, like Friedrich Nietzsche.
Eichmann's self-characterization seems at first to be a case in point for Adorno and Horkheimer's argument. But Arendt quickly points out the flaws in his "reading" of Kant. Murder can obviously never be the basis for a universal law. What Arendt finds striking is the half-way enlightenment that seems to have taken place: the way that Eichmann, as a social climber, has identified Kant as someone worth imitating and quoting, but he has perverted his thought by substituting an outside authority for his own reason: that of the Führer. Arendt observes that this tendency is common to Germans, without saying why. By painting this as a "German" tendency, Arendt implicitly draws a line between Nazism and previous forms of German authoritarianism, like the aristocratic military culture of Prussia at the end of the nineteenth century.
By charging Eichmann with a failure to "think," that is, to recognize the authority of his own reason, Arendt is defending precisely the autonomy of moral judgment for which Kant advocates with his categorical imperative. To act in such a way that our actions could be the basis of a universal law means that we are free to reflect morally without the intermediary of a religious or political authority. Freedom of thought, when it is exercised, becomes the basis for the kinds of moral judgments that successfully resisted Nazism: the brave actions of the Danish and Italian governments, for example, who refused to turn over their Jewish populations. Arendt's later work would build on this insight, and the centrality of the actions of thought and judgment, to paint Kant as a political philosopher, though he never wrote a work of political philosophy.
