 If Weber was the first decisive personal influence and Kant was the first decisive philosophical influence on Jaspers, in the early 1920s he encountered a further figure who assumed a decisive role in his formation: that is, Martin Heidegger. It cannot be claimed without qualification that Heidegger directly determined the conceptual structure or underlying preconditions of Jaspers’s work, nor that Heidegger assimilated aspects of Jaspers’s thought into his own philosophy. Throughout their theoretical trajectories, the differences between Heidegger and Jaspers were in many ways greater than the similarities. Indeed, the theoretical controversies between them eventually culminated in an embittered personal and political altercation, caused by Heidegger’s publicly declared sympathy for the National Socialists in 1933. Jaspers felt himself personally threatened by Heidegger’s infamous decision to support the Nazis, as he was married to a Jewish woman, and he had previously attached himself to eminent liberal politicians and philosophers, most notably Weber, who were now vilified by Heidegger and other intellectuals attached to the NSDAP. In 1933, Jaspers himself was briefly tempted into making certain incautiously optimistic statements about the Hitler regime. Indeed, these were remarks were not entirely out of keeping with his other publications of the early 1930s. In the last years of the Weimar Republic he published a controversial political work, Die geistige Situation der Zeit (The Spiritual Condition of the Age, 1931), which—to his later acute embarrassment—contained a carefully worded critique of parliamentary democracy. Throughout this period, he also stressed the relevance of Weberian ideas of strong leadership for the preservation of political order in Germany. The souring of his relations with Heidegger, however, seems to have hardened his mind into a strict and sustained opposition to National Socialism, and, unlike Heidegger, his works of the 1930s avoided political themes and were largely concentrated on elaborating the interior or religious aspects of his philosophy. In 1932, he published his trilogy Philosophie, consisting of three separate volumes, each based on its own object of transcending: Weltorientierung (Orientation of the World), Existenzerhellung (Illumination of Existence) and Metaphysik (Metaphysics). This book is generally considered as his magnum opus and he testified in retrospect that is was the closest work to his heart. The choice not to grant the book the expected title of “Existential Philosophy”, despite the extensive use of the term Existenzphilosophie, reflects his discontent about its narrowing his guiding ideal of Philosophia Perennis. Later in his Vernunft und Widervernunft in unserer Zeit (Reason and Anti-Reason in Our Time), from 1950 he would express his preference for the expression ‘philosophy of reason’.