He then moved to the University of Tübingen, where he took up a professorship in systematic theology. His work in the years from 1900 to 1918 focused on historical theology. From 1919 Adam's work dealt predominantly with systematic theology. In these years he advocated ecumenism and criticised structures and hierarchies in the church that he saw as outmoded. Upon taking the position at Tübingen in 1919 he publicly declared his intention to continue the tradition of the Tübingen school, which emphasised scholarly dialogue between Catholic and Protestant theologians. He would remain at Tübingen for three decades, where his work focused on the critique of the church, the critique of modernity, and the development of a contemporary theology. In this period he also drew on the tradition of Lebensphilosophie, a school of thought rooted in German Romanticism that emphasised the interconnectedness of life. This aspect of his work, along with his use of the German language rather than Latin and his emphasis on the humanity of Jesus, once again drew scrutiny from the Holy Office, and his book The Spirit of Catholicism (1924) was threatened with placement on the Index Librorum Prohibitorum in 1932. Eventually, however, he was informed that neither The Spirit of Catholicism nor Christ Our Brother (1927) or The Son of God (1933) would be condemned provided he made certain revisions to the texts, which he did in 1933. Nazi era Adam was one of several German Catholic theologians who sought rapprochement between the church and Nazi Germany after Adolf Hitler's rise to power. He saw his role as that of a mediator between the church and the Nazi regime, and envisioned a new relationship between the church and state in which the church would exert a greater influence as part of a corporatist or communitarian system. While other Catholic theologians at Tübingen did not publicly oppose the Nazi regime, Adam was unusual in publicly seeking to mediate between the church and the regime. Nonetheless, he never became a member of the Nazi Party. Early 1930s In his 1933 essay "German Nationality and Catholic Christianity" ("Deutsches Volkstum und katholisches Christentum") Adam argued that the German nation should be primarily the domain of Christians of German heritage, rather than being a pluralistic, secular society. The essay examined the relationship between Catholicism and the "German race" in terms of the relationship between nature and grace. Building on an argument made