A thousand years ago, Ibn Sina, or Avicenna as he was later known in Europe, wrote one of the all-time most important and influential books on psychology. He wrote it in Arabic. It was translated into Latin a hundred and fifty years later, but until now there has been no English version, and so it has been unavailable to many people interested in psychology. The book covers a wide range of topics, from mathematics to mysticism, from biology to moral philosophy, but the major focus is on how we perceive and think about the world. Some of his theories foreshadow recent psychology. For example, his account of perception and memory follows an information-processing model. He uses this model to explain hallucinations, and how we often reconstruct rather than remember past events. On the other hand, some theories are very different. His account of vision, although explaining many everyday phenomena, is quite unlike the present-day one.

The book is historically important because of its great influence on medieval and early modern thinking about psychology. But many of the ideas are still relevant and thought-provoking today.