This is the first discussion in English of the ethical implications of German liberal theology in the early years of the twentieth century. It avoids pejorative interpretative categories (such as `culture protestantism'), seeking instead to understand a much neglected period on its own terms. The leading figure, Ernst Troeltsch (1865-1923), is treated as a `public theologian', engaging at many different levels with his social and political context and trying to ensure that religion could continue to shape the future course of history. To understand his context he made use of the tools of the emergent discipline of sociology and also entered into dialogue with philosophers and historians. Troeltsch's public theology is contrasted with other liberal models of theology, particularly those of the New Testament scholar Wilhelm Bousset and the systematic theologian Wilhelm Herrmann, who were far more reluctant to engage seriously with their context and as a result isolated religion from its wider social and intellectual setting. Troeltsch's theological solution is also compared with Max Weber's sociological response to the problems of modernity: Troeltsch's ideas of cultural synthesis are seen as both constructive and critical and as having much to contribute to contemporary social and political theology.