Answer
The philosopher in question who corresponded with Morgenthau was Hannah Arendt. Arendt, renowned as a political theorist, is best known for her reflections on the concepts of totalitarianism, the banality of evil, and the nature of political power. Her interactions with Morgenthau, a fellow political thinker, provided a space for intellectual exchange and cross-disciplinary insights, contributing to the broader development of political thought in the 20th century.