This illuminating book, by Daniel Kahneman, begins by noting that we have to name things before we can study them. The title indicates the objects of study – two different kinds of thinking. One of the pleasures of reading this book is that one recognizes immediately the thinking he is describing, both the fast and the slow.

Fast thinking he calls System 1: it is the intuitive thinking that enables us to operate instantaneously in a complex world; it is the thinking that constructs our understanding of space and time, our automatic comprehension of human feelings and responses, and our practice of habitual skills.  At its most rapid this kind of thinking takes evasive action in a potential road accident before it happens.System 2 is the slow thinking we call on when asked to weigh probabilities, do computations, fill in tax forms. Unlike System 1 it is effortful and, since we are all lazy, we only do it when we have to. It takes energy and excludes distracting happenings from our attention. We have to concentrate.

An interesting aspect of this book is the way this aspect of psychology has become scientific. (“Science is the mathematization of knowledge.”) It was discovered that there are several physical responses to switching on System 2. One is the dilation of the pupil; another is the reduction in blood sugar. Both of these can be measured and the reality of the two systems is thus objectively confirmed.

In education we call on our students to exercise System 2. It might be interesting to make them aware of the two systems (a background to ELLI?).