How is it possible to imagine what is unknown and therefore unimaginable? How can the unimaginable be represented? On what materials do such representations rely? These questions lie at the heart of this book. Copernican theory redefined the role and importance of the imagination even as it implied the moment of its crisis. Based on this claim, Ladina Bezzola Lambert analyzes seventeenth-century astronomical texts – particularly descriptions of the moon and treatises written in support of the theory of the plurality of worlds – to show how early modern astronomers questioned the role of the imagination as a tool to visualize the unknown, but also how, pressed by the need to support their theories with convincing descriptions of other potential worlds, they sought to overcome the limitations of the imagination with a sophisticated rhetoric and techniques more commonly associated with poetic writing. The limitations of the imagination are at once a problem that all of the texts discussed struggle with and their recurrent theme. In the first and last chapter, the focus shifts to a more explicitly literary context: Ariosto’s Orlando furioso and the work of Italo Calvino. The change of focus from science to literature and from the narratives of the past to contemporary ones serves to emphasize that the issues relating to the imagination, its limitations and creative means, are basically the same both in science and literature and that they are still relevant today.