Quantum physics is believed to be the fundamental theory underlying our understanding of the physical universe. However it is based on concepts & principles that have always been difficult to understand & controversial in their interpretation. This book aims to explain these issues using a minimum of technical language & mathematics. After a brief introduction to the ideas of quantum physics the problems of interpretation are identified & explained. The rest of the book surveys describes & criticises a range of suggestions that have been made with the aim of resolving these problems; these include the traditional or Copenhagen interpretation the possible role of the conscious mind in measurement & the postulate of parallel universes. This new edition has been revised throughout to take into account developments in this field over the past fifteen years including the idea of consistent histories to which a completely new chapter is devoted.