In her Letters on Natural Philosophy, published originally in Krakow in 1584, Camilla Erculiani proposed her new theory of the natural causes of the universal flood in the biblical book of Genesis. Erculiani weaves together her understanding of Aristotelian, Platonic, Galenic, and astrological traditions and combines them with her own observations of the world as seen from her apothecary shop in sixteenth-century Padua. This publication brought Erculiani to the attention of the Inquisition, which accused her of heresy, silencing her for centuries.  This edition presents the first full English translation of Erculiani’s book and other relevant texts, bringing to light the cultural context and scientific thought of this unique natural philosopher.