Preface Ibn Sina, or Avicenna as he was known in Christian Europe, wrote many books, including some about psychology. His main work on psychology is in Arabic. It was translated into Latin as the Liber de Anima by Dominicus Gundissalinus and Ibn Dawud in the last half of the twelfth century. To the best of my knowledge, there has been no translation into any other language. It seemed to me odd that this important book about psychology had no English translation, as English, for better or worse, is unquestionably the language of present-day psychology. Hence, very reluctantly, I decided to attempt it myself. The main part of this book is a translation from the Latin of the Liber de Anima, not from the original Arabic. This is mainly because I cannot read Arabic. However, Gundissalinus’s Latin version, produced around 1150 CE, is important in itself because of its great influence on thinking about psychology in Christian Europe. Gundissalinus’s Latin translation has appeared in a two-volume critical edition, and my English version is based on that text. There are also critical editions of the work in Arabic dating back to the 1950s. If someone were to prepare an English translation from these, I, at least, would welcome it. It would be interesting to know what Gundissalinus and I have got wrong. However, to date no one has undertaken this task, although it has been possible for many years. In the meantime, I offer this version, thinking that Avicenna’s major historical contribution to psychology ought to be more widely available, and particularly to people interested in psychology. I think Avicenna was one of the world’s great psychologists and what he wrote is interesting and important. Many people helped me in this work. I should particularly mention Usman Afzili, who immediately saw the point of the project, and Chris Jones, whose early enthusiasm for it was decisive in my undertaking it at all. Lisa Rolston made helpful comments. A number of other colleagues at the University of Canterbury showed much more interest in the ideas than I had expected. Samantha Armitage and Aimee Claasens were of great help with marketing. My thanks are due to Talya Wilson for the cover design. Nicky Morton read and commented on much of the work. Finally, my wife, Cora Baillie, read an entire early draft, advised on a number of issues, and helped me to improve the sense.