In this book the author analyses the philosophical problems and nature of science, technology and medicine. It is argued that the goal of basic science (truth) makes it important to distinguish it from other types of research. The methodology of science can be viewed as a useful tool for scientific research and it should therefore be evaluated with respect that goal. But the main focus of the book is on the structure and dynamics of technological change. What implications do the goals of technology have for its rationality? How can the pragmatic problem of induction be solved within a fallibilist and skeptical context? The social context is shown to be of vital importance for the goal of technology (usefulness) and its rational development. This has important consequences for how to design a techno policy in society. A rational technological development needs technological pluralism since knowledge of what is useful is scattered among millions of users. The central themes and conclusions of this discussion can also be applied in analyzing the structure and dynamics of medicine. What is the goals and means of medicine? How can we increase the rationality of medical decisions and make use of all available knowledge, not just medical and scientific knowledge? How should we make a distinction between rational medicine and quackery?