Around two hundreds years ago philosophers and scientists began to think about thought experiments. Hans-Christian Ørsted introduced the technical term thought experiments in 1811. But it was Ernst Mach who coined the term "Gedankenexperiment" for philosophical debate at the beginning of the 20th century. Serious investigation into thought experiments began only in the 1980s. In this course the different epistemologies of thought experiments will be explored and many of the paradigmatic thought experiments will be discussed.