This compendium of terms is testament to the fact that critical thinking entails a body of concepts and principles which, when internalized and practiced, enable people to raise their thinking to a higher level. It entails the primary terms in critical thinking as well as many secondary terms, and illuminates these terms as a network of interrelated meanings. The authors have also included a significant number of terms that illuminate the barriers to the development of critical thought — for example those terms which center around the problems of sociocentric and egocentric thought. For most entries the authors provide a brief definition followed by elaboration and exemplification of the concept. In a number of cases the authors link the terms to instruction, for the benefit of readers who are educators or students.