The objective of the book is to resolve one of the many enigmas posed by the history of Ibero-Romance dialects in general and Spanish in particular - the strange palatalization (unconditioned, sporadic and incomplete) of /s/. Over and above this central concern, the book also pursues a fundamentally theoretical aim inspired by two preoccupations of a metalinguistic nature, the delimitation of historical linguistics and the circumstantial nature of linguistic investigation.