What Is Christianity?
Das Wesen des Christentums emerged from sixteen lectures Adolf von Harnack delivered at the University of Berlin during the winter semester of 1899-1900. The distinguished church historian addressed packed auditoriums that included not only theology students but professors from other faculties and members of the educated public. Harnack aimed to distill what he considered the essential core of Christianity from nearly two millennia of historical development, theological elaboration, and institutional accretion.
Harnack argues that Christianity's essence lies in the simple gospel Jesus preached: the fatherhood of God, the infinite value of the human soul, and the commandment of love. He contends that this original message became increasingly obscured by Greek philosophical influences, ecclesiastical hierarchy, and dogmatic formulations. The book traces how the religion of Jesus gradually transformed into a religion about Jesus, with metaphysical speculation replacing ethical transformation. Harnack presents the Reformation as a partial recovery of gospel simplicity, but argues that further stripping away of non-essential elements remains necessary. He champions an undogmatic Christianity focused on personal piety, ethical living, and social responsibility rather than credal orthodoxy or sacramental systems.
The work became one of the most influential and controversial theological books of the early twentieth century, sparking debates that shaped liberal Protestantism and provoked vigorous responses from orthodox theologians like Karl Barth. Harnack's historical-critical method and his attempt to separate the "kernel" of Christianity from its "husk" influenced generations of biblical scholars and church historians, even among those who rejected his conclusions.
Who should read this: Readers interested in the development of liberal Protestant theology, the history of biblical criticism, or the intellectual foundations of modern Christianity will find this essential. Those committed to traditional Christian orthodoxy should approach it as a significant historical document of theological liberalism rather than a constructive guide to faith.
