While much of contemporary syntax equates grammatical structure with hierarchical organization, i.e. tree structures, this book argues for a critical reassessment of that premise. It argues that a crucial part of the description of German clausal syntax should be based on linear, rather than hierarchical concepts. This is done here by adopting 'topological fields'–a concept from traditional descriptive theory. Such fields are defined as syntactic position classes, that is, clusterings of continuous syntactic material, and are defined orthogonally to constituency. This idea is implemented in an extension of Head-Driven Phrase Structure Grammar that employs a separate level of flat linear organization called 'order domain'.