This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book deals with concepts and techniques used in the identification, analysis and assessment of arguments. It introduces the concept of argument as it should be understood for the purposes of critical thinking. The book also deals with a detailed discussion of various ways in which language can obscure an arguer’s intended meaning. It also introduces validity and soundness, the main concepts required for the analysis and assessment of deductive arguments. The book explores the techniques required for reconstructing arguments and discusses specific issues that tend to arise in practice. It is concerned with further concepts and techniques for argument-assessment. The book considers some of the philosophical issues underlying the concepts and techniques used and provide some connections to philosophical questions in the theory of knowledge.