This book is about the conduct of cognitive science, rather than what cognitive science is. The objectives of the book are essentially three. Firstly, the book describes the birth of cognitive science. Secondly, it outlines the method of inquiry which characterizes cognitive science, and through which it is defined. The method employed is constructive, and is carried out by means of the techniques of artificial intelligence, relying on the assumption that mental activity is in principle reproducible by a computer program. Thirdly, the book describes the state of the art in the relevant domains, with a particular attention to application fields like pedagogic, human/machine interaction and psychotherapy. The developmental approach is emphasized and each chapter highlights the fact that developmental aspects are essential to comprehend the steady mode of functioning that is achieved once a person has reached total maturity.Cognitive science is not presented as a definitive method for the analysis of themind. However the author's conclusion is that it is the best of all possible methods today.The technical sections of the book are introduced without presuming that the reader has a greater understanding of the subject than that of a high school student. This means that the book is readable both by experts for its methodological and original parts, and by novices as a coherent critical introduction to the field.