Othmar Maeser, MD, is a specialist in psychiatry and neurology and has been in private practice and as an expert witness in Feldkirch, Austria, for over 27 years. In this book the basic principles of diagnostics, classification and systematics in psychiatry and medicine are presented. This is possible with the help of the philosophy of Immanuel Kant. Through the basis of knowledge, the difference between university medicine and psychiatry as well as that to alternative medicine, complementary medicine and psychosomatics can be made clear. The consequences of the basis of knowledge are presented and discussed for practice and science. Because psychiatry has not paid attention to the basis of its knowledge for several decades, it is in danger of losing its rationally based structure and fragmenting as a science. The book is primarily addressed to physicians, but also to all others who are interested in the fundamentals of knowledge in the field of medical science and other disciplines of healing.