As any quick survey of the syntactic literature will show, there are almost as many different views of ergativity as there are so-called ergative languages (languages whose basic clause structure instantiates an ergative case-marking or agreement pattern). While ergativity is sometimes referred to as a typological characteristic of languages, research on the phenomenon has made it more and more clear that (a) languages do not fall clearly into one or the other of the ergative/absolutive vs. nominative/accusative categories and (b) ergative characteristics are not consistent from language to language. This volume contributes to both the theoretical and descriptive literature on ergativity and adds results from experimental investigations of ergativity. The chapters cover overview approaches within generative, typological, and functional paradigms, as well as approaches to the core morpho-syntactic building blocks of an ergative construction (absolutive case and licensing, and ergative case and licensing); common related constructions (anti-passive); common related properties (split-ergativity, syntactic vs. morphological ergativity, word order, the interaction of agreement patterns and ergativity); and extensions and permutations of ergativity (nominalizations, voice systems). While the editors all work within the generative framework and investigate the syntactic properties of ergativity through fieldwork, and many of the chapters represent similar research, there are also chapters representing different frameworks (functional, typological) and different approaches (experimental, diachronic). The theoretical chapters touch on many different languages representing a wide range of language families, and there are sixteen case studies that are more descriptive in nature, attesting to both the pervasiveness and diversity of ergative patterns.