ABSTRACT
This book is about thinking and reasoning construed as a scientific project. That is, it presents the most up-to-date account of current scientific thinking on the human activity of thinking and reasoning. Thus conceived, this is clearly a descriptive project. One might therefore query why this chapter and Chapter 19 introduce fundamentally normative concepts like logic and probability. These are theories of how people should reason, not how they actually reason. However, there are important reasons why understanding these normative projects is crucial in this area.
