What do all languages have in common, and what gives each language its individuality? Language typology, which has developed in response to these fundamental questions, is concerned with the construction of theoretical frameworks capable of delimiting the range of possible human languages and of capturing constraints on cross-linguistic variation. Language typology is a major concern of all contemporary schools of linguistics, yet a coherent image of the field is difficult to form because of the diversity of theoretical orientations and practical methodologies. This collection brings together for the first time original contributions from major schools of typological research, from the Prague School to the Generative Grammar tradition. Leading scholars offer first-hand accounts of the theoretical foundations and substantive findings of their particular school of thought, clarifying basic assumptions which are often not explicitly stated in the literature. The collection as a whole provides both a survey of the place of individual typological schools in the historiography of the subject and a comprehensive account of the present state of language typology in an international context. It gives an overview of both the underlying unity of and the differences in the methods employed in the field.