In the centuries since Descartes famously proclaimed, ''I think, therefore I am,'' science has often overlooked emotions as the source of a person''s true being. Even modern neuroscience has tended until recently to concentrate on the cognitive aspects of brain function, disregarding emotions. This attitude began to change with the publication of <i>Descartes'' Error</i>. Antonio Damasio challenged traditional ideas about the connection between emotions and rationality. In this wonderfully engaging book, Damasio takes the reader on a journey of scientific discovery through a series of case studies, demonstrating what many of us have long suspected: emotions are not a luxury, they are essential to rational thinking and to normal social behaviour.