This book was written to try to integrate various strands of concern about communication, language, and thinking. There are two related questions that have served to initiate the enquiries that resulted in this book: Why do people hold false beliefs? And why do they accept and use inadequate arguments in support of their beliefs? The author has provided a clear conceptual framework to address these issues and in doing so he folds into the arguements the marvelous richness of language as a vehicle of communication.