 Thought experiments are basically devices of the imagination. They are employed for various purposes such an entertainment, education, conceptual analysis, exploration, hypothesizing, theory selection, theory implementation, etc. Some applications are more controversial than others. Few would object to thought experiments that serve to illustrate complex states of affairs, or those that are used in educational contexts. The situation is different, however, with respect to the appropriation of imagined scenarios to investigate reality (very broadly conceived to include things like electrons, tables, rain, beliefs, morals, people, numbers, universes, and even divine beings). It is this use of thought experiments that attracts most of the attention inside and outside of philosophical discourse. Significant is the overlap here with many other central philosophical topics, such as the nature of the imagination, the importance of understanding in contrast to explanation, the role of intuition in human cognition, and the relationship between fiction and truth. Moreover, thought experiments are interdisciplinary in two important respects. Firstly, not only philosophers study them as a research topic, but also historians, cognitive scientists, psychologists, etc. Secondly, they are used in many disciplines, including biology, economics, history, mathematics, philosophy, and physics (although, interestingly, not with the same frequency in each).