 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, preserving their letters but keeping them unavailable.The relationship was not known until Elisabeth Young-Bruehl's biography of Arendt appeared in 1982, by which time Arendt and Heidegger had both died, though Heidegger's wife, Elfride (1893–1992), was still alive.