Anjum P. Saleemi argues that the acquisition of language as a cognitive system can properly be understood by pairing the formal approach to learning, often known as learnability theory, with Chomsky's theory of Universal Grammar and its claim that human language is innately constrained, with some predefined space for variation. Focusing on specific areas of syntax, such as binding theory and the null subject parameter, Dr Saleemi unites learnability theory's methodology with Chomsky's principles-and-parameters model, and construes acquisition as a function of linguistic principles with largely domain-specific learning procedures, mediated by environmental input. The aim of this study is to show that a self-contained linguistic theory cannot by itself be psychologically plausible, but depends on a compatible theory of learning which embraces developmental as well as formal issues.