Julia Webers book demonstrates how Aristotles understanding of virtual forces as undetectable but nonetheless effective has shaped philosophical discourse up until the modern age. It traces developments from philosophical debate about the existence of virtual forces in antiquity and the Middle Ages to the emergence of virtual spaces in the early modern period, and the appearance of virtual worlds in 18th-century literature. In this way, it reveals the seldom traced continuities and shifts between ancient philosophical discussion of forces and contemporary virtual realities.