This well-edited collection of papers responds to the theoretical issues that concerned Clive Perdue throughout his productive career. The 29 Chapters examine similarities and differences between monolinguals, childhood bilinguals, and adult and child learners of a second language. We see how learner productions are influenced by perceptual abilities, l 1 transfer, and explicit learning as they operate across the lifespan, rather than some uniform expiration of a critical period.Brian MacWhinney, Carnegie Mellon University, USAIn this volume, written by collaborators and friends of Clive Perdue, we find both familiar themes such as the expression of meaning in language, and unfamiliar ones such as the critical period, evolution, and signed language. Well-studied migrant workers provide data as do new populations (tutored learners, child l 2ers, near native adult l 2ers, bilinguals). What binds the contributions is a concern with simpler linguistic systems. A worthy tribute to Clive's intellectual legacy.Susanne Carroll, University of Calgary, Canada