One of the most influential developments in the cognitive sciences in the last 20 years is Phil Johnson-Laird's theory of mental models. This theory aims to provide a detailed account of both reasoning and inference, on the one hand, and language processing on the other. Mental models theory can therefore be regarded as a step toward the much-sought-after unified theory of cognition. This book, to be published on the occasion of Phil Johnson-Laird's sixtieth birthday, provides an overview of the current state of mental models research. It also reflects Phil's influence on the development of cognitive science at a more personal level. The authors include some of Phil's most distinguished collaborators and the majority of his former graduate students, many of whom are now eminent psychologists in their own right. The book contains contributions from North America, Britain, and the rest of Europe, and covers all the main strands of mental models theory.