Originally published in 1975, this volume contains original reports of new models and data in the areas of propositional reasoning, syllogistic reasoning, and transitive inference in children and adults of the time. A wide range of theoretical viewpoints is represented, and an effort is made to integrate the models and empirical findings, as well as place them in a common perspective and elucidate the general issues and questions relevant to these various approaches. The study of logical reasoning was undergoing rapid expansion at the time and this volume brings together the latest thinking in the area, in such a way that the relation between Piagetian and non-Piagetian traditions are examined, as well as the connection between the study of reasoning and the area of linguistic inquiry. The discussions of metatheoretical issues, such as the notion of logical competence and separability of representation and logical processing, as regards the various models presented herein, made this volume required reading for all those interested in reasoning in children and adults at the time.