Combining empirical scrutiny and insightful theoretical discussion, Malte Rosemeyer provides an up-to-date analysis of perfect auxiliary selection in the history of Spanish. He takes into account a wide variety of potential determinants of the choice between HAVE and BE auxiliary forms, and offers a critical assessment of their relative importance and interrelatedness. More generally, this study significantly advances our understanding of the gradualness of morphosyntactic change, and of the role of frequency in diachronic explanation.

- Andreas Dufter, University of Munich,

This is a fascinating exploration of the diachronic change in the auxiliary selection system between Old and Early Modern Spanish. Drawing on work in linguistics, corpus analysis, and statistical modelling, the author presents an account that is not only comprehensive in its coverage of the interacting factors leading to increasing variation in auxiliary choice, but also rigorous in its theoretical reanalysis of this phenomenon. The book is invaluable and inspiring reading for linguists, variationists, and acquisitionists regardless of theoretical orientation.

- Antonella Sorace, The University of Edinburgh,