  One of the most complex questions in Cardano’s philosophy as a whole concerns the relationship between nature and the soul. This is a point where Cardano’s multiple allegiances (scholastic Aristotelianism, Plotinian Platonism, medicine and astrology) come to the fore. Inevitably, it is also an area where not a few frictions among different traditions come to the fore. Among Cardano’s desiderata there was the plan to devote a specific philosophical treatise to the notion of nature. It is an unfinished work that in all likelihood he sketched at the beginning of the 1560s, De natura liber unicus. It can be seen as part of a series of treatises devoted to the exploration of the most recondite aspects of the natural, supernatural and moral worlds (De libris propriis, OO, I, 119; ed. Maclean, 293). De natura demonstrates Cardano’s lifelong engagement with notions of naturalism, universal animation, and teleology. The discussion is opaque at times because of the topic’s difficulty, the characteristic obscurity of Cardano’s disjointed and elliptical writing, and the precarious condition of the text, left unfinished, with several gaps and marks of typographical sloppiness (typos, mistakes, and missing words). On the other hand, being a monographic treatment of the meaning of nature, the treatise holds great significance, all the more so because, as Cardano explains, the investigation of nature (inquisitio naturae) sheds light on the very origin of things, including human beings (De natura, OO, II, 283a). In this sense, fragmentary as it may be, Cardano’s De natura is an attempt to outline the ultimate principles of reality (on the relationship between natural and supernatural phenomena in Cardano, see Siraisi 1997, 149–173).