Integrational Linguistics (IL), developed by the German linguist Hans-Heinrich Lieb and others, is an approach to linguistics that integrates linguistic descriptions, construed as declarative theories, with a detailed theory of language that covers all classical areas of linguistics, from phonology to sentence semantics, and takes linguistic variation, both synchronic and diachronic, fully into account. The aim of this book is to demonstrate how some controversial issues in language description are resolved in Integrational Linguistics. The four essays united here cover nearly all levels of language systems: phonetics and phonology (The Case for Two-Level Phonology by Hans-Heinrich Lieb, on German obstruent tensing and French nasal alternation), morphology (Form and Function of Verbal Ablaut in Contemporary Standard German by Bernd Wiese), morphology and syntax (Inflectional Units and Their Effects by Sebastian Drude, on the person system in Guaran), and syntax and sentence semantics (Topic Integration by Andreas Nolda, on split topicalization in German).