One of the peculiarity literary productions of Capuchins in the Seventeenth Century was El ente dilucidado, written by Priest Antonio de Fuentelapena. It is a composition that pursues a philosophical nature to unravel the nature of metaphysical entities (particularly the nature of the elves) and contains the final dissertation on the man’s air capabilities. One of the aims of the author was to banish the fear for elves, as it was popularly believed; they were evil spirits, ghosts or souls harmful to man. The article discusses how Fuentelapena argued the nature of the elves and their role in the metaphysical world. We will finish with some considerations on the rereading that the text deserves in the light of the history.