The knowledge of the secrets of nature was in fact central to magic, a field which had an ambiguous relationship to natural philosophy. If a natural philosopher wanted to describe and understand nature, a practitioner of magic wanted to investigate it and its occult properties in order to master it. The Neoplatonic correspondences between macrocosmus—the world—and microcosmus—man—allow magic to exercise its power on a reality which was seen in vitalistic and transcendental terms: the book of nature for practitioners of magic was not the same one as that of the Aristotelians or of Galileo, but it is written with signs and allusions. Magical doctrines had a wide circulation throughout the Middle Ages, but were enriched in the fifteenth century by the rediscovery of the Corpus Hermeticum. The Corpus was a collection of heterogeneous texts, dealing both with practical magic and the mystical teachings attributed to Hermes Trismegistus, an Egyptian sage who purportedly lived at the time of Moses and was first in the lineage of a tradition of wisdom (the so-called sapientia perennis). The alleged antiquity of the Corpus represented the strongest evidence of its authority and reliability, and thinkers like Marsilio Ficino in his De vita, and then Cornelius Agrippa (1486–1535) in his De occulta philosophia, proposed doctrines based on it. Their readers were encouraged to carve talismans and images, and surround themselves with precise colors or herbs connected to planetary influences in order to exploit the conjunction of the whole, a living being of which man is both part and lord. Magical treatises included recipes and empirical descriptions, and in his De augmentis Scientiarum even Francis Bacon described magic as an operative knowledge of hidden forms and the harmony of things, which displays the wonderful works of nature. The connection between micro and macrocosmus also underlay medical practice—as in the case of Ficino himself and later Paracelsus—and disciplines like physiognomy, which was considered part of the Aristotelian natural encyclopedia. Della Porta’s De physiognomia humana (1586), which was mainly a collection of past authorities that included ethical problems and was accompanied by illustrations, became the standard text on the topic until Lavater.  There were also expressly hermetic approaches to the subject, including the one by Robert Fludd (1574–1637).