As one of the few books in English on Christian Thomasius (1655–1728) – at the time of writing there is only one other – the present work carries significant responsibilities on behalf of its readers. It must render accessible a life and mind shaped by circumstances now quite unfamiliar – those of an academic jurisconsult to a princely state of the Holy Roman German Empire – while simultaneously doing justice to the most recent scholarship on Thomasius, most of which is in German. Above all, though, it must show what it is about Thomasius's writings that makes them historically significant, and why they should claim the interest of Anglophone readers today, three hundred years after his life and times.

The historical significance of Thomasius's writings has been much contested, fluctuating, sometimes radically, with shifts in the cultural and political circumstances of their reception, and with the forms of historiography and philosophy dominant in these circumstances. During his life he was attacked as a heterodox innovator by those whom he attacked for their authoritarian scholasticism and ‘political papalism’: the juristic and theological defenders of the Lutheran confessional state. Yet, among his students and in ‘enlightened’ circles in Protestant Germany and Scandinavia, he was widely admired in terms that Thomasius himself had helped to popularise.