Why do we do thought experiments? Philosophers, scientists, visionaries, artists, and creative writers across languages, religious traditions, and cultures have turned to the fascinating genre of the thought experiment, drawing upon its unique affordances of compressed imaginative thinking for a variety of reasons, and to many different ends. Questions that thought experiments address include: How do we know that we exist? How big is the universe? What is time, and can we actually experience the present moment of “now”? How do I know that everything around me is real? This course is intended as a guided tour of the thought experiment genre. We will consider various thought experiments proposed by ancient Greek and medieval Islamic philosophers, early modern poets, twentieth-century scientists, and contemporary fiction writers from around the world. In this course, we ask: how do thought experiments harness the work of metaphor, narrative, and fiction, and what does this imply about the interrelation between thought, knowledge, language, and imagination?