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Marburg (1924–1926)

In Berlin, Guardini had introduced her to Kierkegaard, and she resolved to make theology her major field. At Marburg (1924–1926) she studied classical languages, German literature, Protestant theology with Rudolf Bultmann and philosophy with Nicolai Hartmann and Heidegger. She arrived in the fall in the middle of an intellectual revolution led by the young Heidegger, of whom she was in awe, describing him as "the hidden king reigned in the realm of thinking".

Heidegger had broken away from the intellectual movement started by Edmund Husserl, whose assistant he had been at University of Freiburg before coming to Marburg. This was a period when Heidegger was preparing his lectures on Kant, which he would develop in the second part of his Sein und Zeit (Being and Time) in 1927 and Kant und das Problem der Metaphysik (1929). In his classes, he and his students struggled with the meaning of " Being " as they studied Aristotle 's and Plato 's Sophist concept of truth, to which Heidegger opposed the pre-Socratic term ἀλήθεια. Many years later Arendt would describe these classes, how people came to Marburg to hear him, and how, above all he imparted the idea of Denken ("thinking") as activity, which she qualified as "passionate thinking".

Arendt was restless, finding her studies neither emotionally nor intellectually satisfying. She was ready for passion, finishing her poem Trost (Consolation, 1923) with the lines:

Die Stunden verrinnen, Die Tage vergehen, Es bleibt ein Gewinnen Das bloße Bestehen. (The hours run down. The days pass on. One achievement remains: merely being alive.)

Her encounter with Heidegger represented a dramatic departure from the past. He was handsome, a genius, romantic, and taught that thinking and "aliveness" were but one. The 18-year-old Arendt then began a long romantic relationship with the 35-year-old Heidegger, who was married with two young sons. Arendt later faced criticism for this because of Heidegger's support for the Nazi Party after his election as rector at Freiburg University in 1933. Nevertheless, he remained one of the most profound influences on her thinking, and he would later relate that she had been the inspiration for his work on passionate thinking in those days. They agreed to keep the details of the relationship a secret while preserving their letters. The relationship was unknown until Elisabeth Young-Bruehl 's biography of Arendt appeared in 1982. At the time of publishing, Arendt and Heidegger were deceased but Heidegger's wife, Elfride, was still alive. The affair was not well known until 1995, when Elzbieta Ettinger gained access to the sealed correspondence and published a controversial account that was used by Arendt's detractors to cast doubt on her integrity. That account, which caused a scandal, was subsequently refuted.

At Marburg, Arendt lived at Lutherstraße 4. Among her friends was Hans Jonas, a Jewish classmate. Another fellow student of Heidegger's was Jonas' friend, the Jewish philosopher Günther Siegmund Stern, who would later become her first husband. Stern had completed his doctoral dissertation with Edmund Husserl at Freiburg, and was now working on his Habilitation thesis with Heidegger, but Arendt, involved with Heidegger, took little notice of him at the time.