Marx's crucial experience at Berlin was his introduction to Hegel's philosophy, regnant there, and his adherence to the Young Hegelians. At first he felt a repugnance toward Hegel's doctrines; when Marx fell sick it was partially, as he wrote his father, “from intense vexation at having to make an idol of a view I detested.” The Hegelian pressure in the revolutionary student culture was powerful, however, and Marx joined a society called the Doctor Club, whose members were intensely involved in the new literary and philosophical movement. Their chief figure was Bruno Bauer, a young lecturer in theology, who was developing the idea that the Christian Gospels were a record not of history but of human fantasies arising from emotional needs and that Jesus had not been a historical person. Marx enrolled in a course of lectures given by Bauer on the prophet Isaiah. Bauer taught that a new social catastrophe “more tremendous” than that of the advent of Christianity was in the making. The Young Hegelians began moving rapidly toward atheism and also talked vaguely of political action.
The Prussian government, fearful of the subversion latent in the Young Hegelians, soon undertook to drive them from the universities. Bauer was dismissed from his post in 1839. Marx's “most intimate friend” of this period, Adolph Rutenberg, an older journalist who had served a prison sentence for his political radicalism, pressed for a deeper social involvement. By 1841 the Young Hegelians had become left republicans. Marx's studies, meanwhile, were lagging. Urged by his friends, he submitted a doctoral dissertation to the university at Jena, which was known to be lax in its academic requirements, and received his degree in April 1841. His thesis analyzed in a Hegelian fashion the difference between the natural philosophies of Democritus and Epicurus. More distinctively, it sounded a note of Promethean defiance:
Philosophy makes no secret of it. Prometheus' admission: “In sooth all gods I hate,” is its own admission, its own motto against all gods, . . . Prometheus is the noblest saint and martyr in the calendar of philosophy.
In 1841 Marx, together with other Young Hegelians, was much influenced by the publication of Das Wesen des Christentums (1841; The Essence of Christianity) by Ludwig Feuerbach. Its author, to Marx's mind, successfully criticized Hegel, an idealist who believed that matter or existence was inferior to and dependent upon mind or spirit, from the opposite, or materialist, standpoint, showing how the “Absolute Spirit” was a projection of “the real man standing on the foundation of nature.” Henceforth Marx's philosophical efforts were toward a combination of Hegel's dialectic—the idea that all things are in a continual process of change resulting from the conflicts between their contradictory aspects—with Feuerbach's materialism, which placed material conditions above ideas.