According to Christian theology, fallen angels share key similarities with human beings because they share our outcast condition. Cast to Earth and wandering in search of respite, their chief activity is their engagement and dialogue with humanity. With this probing new contribution to the study of Christianity, Armando Maggi examines this dialogue, exploring how evil spirits interacted with mankind during the early modern period. Reading innumerable treatises on demonology written during the Renaissance, including Thesaurus exorcismorum, the most important record of early modern exorcisms, Maggi finds repeated attempts to define the language exchanged between the fallen progeny of Adam, and the most notorious fallen angel of them all, Satan. Using points of departure taken from de Certeau and Lacan, Maggi shows that Satan articulates his language first and foremost in the mind. More than speaking, the devil tries to make human beings understand his language and speak it themselves. Through sodomites, infidels, and witches, then, the devil is able to infect humanity as it appropriates his seductive rhetoric.