This chapter introduces philosophies of science based on the notion that science functions within structures of theories, where some theories are fundamental and protected from falsification. A short piece of fiction illustrates this notion. Building on this story, Kuhn’s paradigms are introduced, including the concepts of scientific revolutions, paradigm shifts and incommensurability between paradigms. Some problematic aspects of paradigms are mentioned, such as the seeming lack of real scientific revolutions historically and whether progress and preservation of knowledge in science are really possible given the incommensurability between paradigms that replace each other. It is acknowledged that paradigm thinking has had a strong lasting role both within science and in society, but not always in a way Kuhn would have recognised. Lakatos’ research programmes are introduced as a similar but different approach, and the ‘new experimentalism’ is mentioned as a quite different way of dealing with theory-dependence and theory structures in science.