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?