Can one do evil without being evil? This was the puzzling question that the philosopher Hannah Arendt grappled with when she reported for The New Yorker in 1961 on the war crimes trial of Adolph Eichmann, the Nazi operative responsible for organising the transportation of millions of Jews and others to various concentration camps in support of the Nazi’s Final Solution.

Arendt found Eichmann an ordinary, rather bland, bureaucrat, who in her words, was “neither perverted nor sadistic”, but “terrifyingly normal”. He acted without any motive other than to diligently advance his career in the Nazi bureaucracy. Eichmann was not an amoral monster, she concluded in her study of the case, Eichmann in Jerusalem: A Report on the Banality of Evil (1963). Instead, he performed evil deeds without evil intentions, a fact connected to his “thoughtlessness”, a disengagement from the reality of his evil acts. Eichmann “never realised what he was doing” due to an “inability...to think from the standpoint of somebody else”. Lacking this particular cognitive ability, he “commit[ted] crimes under circumstances that made it well-nigh impossible for him to know or to feel that he [was] doing wrong”.

Arendt dubbed these collective characteristics of Eichmann “the banality of evil”: he was not inherently evil, but merely shallow and clueless, a “joiner”, in the words of one contemporary interpreter of Arendt’s thesis: he was a man who drifted into the Nazi Party, in search of purpose and direction, not out of deep ideological belief. In Arendt’s telling, Eichmann reminds us of the protagonist in Albert Camus’s novel The Stranger (1942), who randomly and casually kills a man, but then afterwards feels no remorse. There was no particular intention or obvious evil motive: the deed just “happened”.

This wasn’t Arendt’s first, somewhat superficial impression of Eichmann. Even 10 years after his trial in Israel, she wrote in 1971:

I was struck by the manifest shallowness in the doer [ie Eichmann] which made it impossible to trace the uncontestable evil of his deeds to any deeper level of roots or motives. The deeds were monstrous, but the doer – at least the very effective one now on trial – was quite ordinary, commonplace, and neither demonic nor monstrous.

The banality-of-evil thesis was a flashpoint for controversy. To Arendt’s critics, it seemed absolutely inexplicable that Eichmann could have played a key role in the Nazi genocide yet have no evil intentions.

Gershom Scholem, a fellow philosopher (and theologian), wrote to Arendt in 1963 that her banality-of-evil thesis was merely a slogan that “does not impress me, certainly, as the product of profound analysis”. Mary McCarthy, a novelist and good friend of Arendt, voiced sheer incomprehension: “[I]t seems to me that what you are saying is that Eichmann lacks an inherent human quality: the capacity for thought, consciousness – conscience. But then isn’t he a monster simply?”

The controversy continues to the present day. The philosopher Alan Wolfe, in Political Evil: What It Is and How to Combat It (2011), criticised Arendt for “psychologising” – that is, avoiding – the issue of evil as evil by defining it in the limited context of Eichmann’s humdrum existence. Wolfe argued that Arendt concentrated too much on who Eichmann was, rather than what Eichmann did. For Arendt’s critics, this focus on Eichmann’s insignificant, banal life seemed to be an “absurd digression” from his evil deeds.

Other recent critics have documented Arendt’s historical errors, which led her to miss a deeper evil in Eichmann, when she claimed that his evil was “thought-defying”, as Arendt wrote to the philosopher Karl Jaspers three years after the trial. The historian Deborah Lipstadt, the defendant in David Irving’s Holocaust-denial libel trial, decided in 2000, cites documentation released by the Israeli government for use in the legal proceeding. It proves, Lipstadt asserts in The Eichmann Trial (2011), that Arendt’s use of the term “banal” was flawed:

The memoir [by Eichmann] released by Israel for use in my trial reveals the degree to which Arendt was wrong about Eichmann. It is permeated with expressions of Nazi ideology...[Eichmann] accepted and espoused the idea of racial purity.

Lipstadt further argues that Arendt failed to explain why Eichmann and his associates would have attempted to destroy evidence of their war crimes, if he was indeed unaware of his wrongdoing.

In Eichmann Before Jerusalem (2014), the German historian Bettina Stangneth reveals another side to him besides the banal, seemingly apolitical man, who was just acting like any other “ordinary” career-oriented bureaucrat.

Drawing on audiotapes of interviews with Eichmann by the Nazi journalist William Sassen, Stangneth shows Eichmann as a self-avowed, aggressive Nazi ideologue strongly committed to Nazi beliefs, who showed no remorse or guilt for his role in the Final Solution – a radically evil Third Reich operative living inside the deceptively normal shell of a bland bureaucrat. Far from being “thoughtless”, Eichmann had plenty of thoughts – thoughts of genocide, carried out on behalf of his beloved Nazi Party. On the tapes, Eichmann admitted to a sort of Jekyll-and-Hyde dualism:

I, “[t]he cautious bureaucrat,” that was me, yes indeed. But...this cautious bureaucrat was attended by a...a fanatical [Nazi] warrior, fighting for the freedom of my blood, which is my birthright...

Arendt completely missed this radically evil side of Eichmann when she wrote 10 years after the trial that there was “no sign in him of firm ideological convictions or of specific evil motives”. This only underscores the banality – and falsity – of the banality-of-evil thesis. And though Arendt never said that Eichmann was just an innocent “cog” in the Nazi bureaucracy, nor defended Eichmann as “just following orders” – both common misunderstandings of her findings on Eichmann – her critics, including Wolfe and Lipstadt, remain unsatisfied.

So what should we conclude about Arendt’s claim that Eichmann (as well as other Germans) did evil without being evil?

The question is a puzzle because Arendt missed an opportunity to investigate the larger meaning of Eichmann’s particular evil by not expanding her study of him into a broader study of evil’s nature. In The Origins of Totalitarianism (1951), published well before the Eichmann trial, Arendt said: “It is inherent in our entire [Western] philosophical tradition that we cannot conceive of a “radical evil”...”

Instead of using the Eichmann case as a way forward to advance the tradition’s understanding of radical evil, Arendt decided that his evil was banal, that is, “thought-defying”.

By taking a narrow legalistic, formalistic approach to the trial – she emphasised that there were no deeper issues at stake beyond the legal facts of Eichmann’s guilt or innocence – Arendt automatically set herself up for failure as to the deeper why of Eichmann’s evil.

Yet in her writings before Eichmann in Jerusalem, she actually took an opposite position. In The Origins of Totalitarianism, she argued that the evil of the Nazis was absolute and inhuman, not shallow and incomprehensible, the metaphorical embodiment of hell itself: “[T]he reality of concentration camps resembles nothing so much as medieval pictures of Hell.”

By declaring in her pre-Eichmann trial writings that absolute evil, exemplified by the Nazis, was driven by an audacious, monstrous intention to abolish humanity itself, Arendt was echoing the spirit of philosophers such as FWJ Schelling and Plato, who did not shy away from investigating the deeper, more demonic aspects of evil. But this view changed when Arendt met Eichmann, whose bureaucratic emptiness suggested no such diabolical profundity, but only prosaic careerism and the “inability to think”. At that point, her earlier imaginative thinking about moral evil was distracted, and the “banality of evil” slogan was born. Moreover, Arendt died in 1975, perhaps if she had lived longer she could have clarified the puzzles surrounding the banality-of-evil thesis, which still confound critics to this day. But this we shall never know.

Thus we are left with her original thesis as it stands. What is the basic confusion behind it? Arendt never did reconcile her impressions of Eichmann’s bureaucratic banality with her earlier searing awareness of the evil, inhuman acts of the Third Reich. She saw the ordinary-looking functionary, but not the ideologically evil warrior. How Eichmann’s humdrum life could co-exist with that “other” monstrous evil puzzled her. Nevertheless, Arendt never downplayed Eichmann’s guilt, repeatedly described him as a war criminal, and concurred with his death sentence as handed down by the Israeli court. Though Eichmann’s motives were, for her, obscure and thought-defying, his genocidal acts were not. In the final analysis, Arendt did see the true horror of Eichmann’s evil.

This article first appeared on Aeon.