When the Eyes Are Shut: The Strange Case of Girolamo Cardano’s Idolum in Somniorum Synesiorum Libri IIII (1562)

In his treatise on dreams Somniorum Synesiorum Libri IIII, published in 1562, the Italian Renaissance philosopher and physician Girolamo Cardano distinguishes between idola and visiones (or visa). Historians have discussed the reasons for such a distinction without taking into account Cardano’s original theory of sense-perception. In this article I shall argue that, in order to interpret the meaning of idola and visiones in Cardano’s theory of dreams, one should bear in mind his view that hearing is superior to sight and that while idola are essentially based on sound, visiones depend on images.