A general introduction to physical phenomena and the way they are related to each other and to mental phenomena. The purpose of this book is to show that the study of both mental phenomena and physical phenomena is indispensable for the development of the eightfold Path. The quotations from the scriptures provide the reader with lively examples of the way the physical phenomena, which are depending on conditions, perform their functions in daily life. The study of this book will help the reader to understand the Buddha's teaching of non-self. This book is suitable for those who already have some knowledge of Buddhism.