Book excerpt: Although the Petersens' name is quite known among specialists of Pietism, their work, their ideas and the development of their thought remain mostly unresearched. Elisa Belucci aims to shed more light on their works, analysing and interpreting them in relationship to the theological and socio-political context. In so doing, she fills some gaps present in the research on these authors: firstly, she analyses the positions presented in the Petersens' work until 1703 at length; secondly, she tries to unearth sources and influences; thirdly, she seeks to comment on the Petersens' ideas and positions in relationship to the historical context. The result is an entangled picture which questions the traditional distinction between "church Pietism" and "radical Pietism", "orthodoxy" and "radicalism/separatism", showing, instead, that these categories are sometimes too narrow to describe the position of certain authors, such as the Petersens.