 While in Berlin, Marcuse began reading Martin Heidegger’s newly published Being and Time with a friend in 1927. Although Marcuse was already a student of philosophy, his interest in philosophy had remained second to his interest in German literature up to this point. The excitement caused by Being and Time would lead Marcuse to a life-long serious engagement with philosophy. According to Douglas Kellner, this move from a primary concern with art to a deeper engagement with philosophy suggests that Marcuse was a bit skeptical about the power of art as a “cognitive source of knowledge and as an instrument of personal liberation and social change” (Kellner 1984: 36–37). The impact of Heidegger was so great that Marcuse returned to Freiburg in 1928 to study philosophy with Heidegger and Edmund Husserl. While in Freiburg Marcuse worked as Heidegger’s assistant and began work on his second dissertation, Hegel’s Ontologie und die Grundlegung einer Theorie der Geschichtlichkeit (Hegel’s Ontology and the Theory of Historicity) (1932 [1987]). Although this dissertation was never approved by Heidegger (and according to Marcuse, perhaps not read), it was published in 1932.