The Introduction outlines the book’s six chapters. Chapter 1 presents the theoretical foundations of Generative Grammar and discusses the ‘prehistory’ of the concept of parameter in the late seventies and early eighties up to the formulation of the Principles and Parameters model of the Government and Binding (GB) framework. Chapter 2 examines the individual formulation of the main parameters that were proposed during that period, summarizing many of the central empirical concerns of research in the 1980s. Chapter 3 traces the development of the concept of parameter in early Minimalism, focusing on the debate over macro- vs. microparameters, the main criticisms raised against the parametric approach, and the latter’s subsequent reformulation within recent hierarchical models. Chapter 4 returns to the parameters of the GB Theory and evaluates their status in current generative theory. Chapter 5 is devoted specifically to the head-complement parameter, whose history arguably embodies the development of the parametric approach to linguistic variation. Chapter 6 draws the conclusions of the historical review conducted in the previous chapters and critically reconsiders the notion of parameter.

Chapter 9 focuses on the claim that the language input that children are exposed to is not rich enough to explain how they can construct a mental grammar. This leads to the poverty of the stimulus argument in support of the Innateness Hypothesis, which holds that if the input is insufficient, children must be born with an innate system that bridges the gap between the poor input and the richness of their knowledge of language. We will examine in detail in which ways the input could be called poor. We then turn to Chomsky’s Principles and Parameters model of language acquisition, paying attention to certain developments in this model that reduced the role of innate knowledge. Along the way we also introduce two additional arguments. The argument from convergence is based on the fact that all learners that grow up in the same speech community end up with (essentially) the same mental grammar despite having received different input. We also mention the argument from speed of acquisition, which is based on the fact that language acquisition is “fast,” no matter how you measure it. We then review alternative, more empiricist, approaches to language acquisition.