Symbolism, allegory, and metaphor pervade Athanasius Kircher’s (1602–1680) Mundus Subterraneus (The Subterranean World). Elements from the communicative theory of semiotics are useful for exploring Mundus Subterraneus and for illuminating the modern reactions to his works. Kircher used Hermetic and Neoplatonic philos ophies as a bridge between medieval thought systems and the growing empirical movement of the Scientific Revolution. In Kircher’s studies, no event was taken in isolation, and his examination of Earth rested with Plato’s philosophy that the world was created by God as a manifestation of his own perfection. From a modern semiotic viewpoint, Kircher used indexical and iconic signs to combine rational and empirical techniques that sustained his holistic view of the cosmos. In the modern ideal formulation of scientific observation and inquiry, indexical signs are acceptable authoritative causal links between observation and interpretation. For Kircher, both indexical and iconic signs were legitimate articles to collect and employ because they were all manifestations of the Divine Mind. Iconic signs could be religious images or conceptual ideas that Kircher projects onto the workings of Earth.