 In his classes he and his students struggled with the meaning of "Being" as they worked together through Aristotle's concept of ἀλήθεια (truth) and Plato's "Sophist".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.