 The fourth book of Del senso delle cose is devoted to natural magic. Approaching the theme of magic, Campanella begins by deploring the vile and decadent condition into which this very noble science has fallen. In modern times, the name magician is given to “superstitious friends of demons” who, instead of dedicating themselves to the patient study of nature, prefer to take a “short cut” by asking demons for things that they cannot provide but that they promise and pretend to be able to do. Della Porta’s attempt to restore this doctrine was entirely praiseworthy but remained insufficient, because he restricted himself to speaking about these arguments solely in a descriptive and empirical manner without supplying philosophical explanations of phenomena. In listing the most bizarre occult properties of minerals, plants and animals in the magical tradition, della Porta maintained that it was not possible to offer a rational explanation of the relations of sympathy and antipathy, of affinity and repulsion, that exist between natural entities and limited himself to delighting in the spectacle and entertainment provided by nature. Campanella, however, took it on himself to reinterpret this tradition in light of his doctrine of the sense of things and of the spiritus. As Pliny the Elder had noted (Natural History, XXX.i-ii), magic, an ancient form of wisdom of Persian origin, is constructed from the convergence of three doctrines: religion, that purifies the soul and imprints faith, honor and reverence on the souls of those toward whom the magical operation is directed; medicine, that makes it possible to understand the powers of herbs, stones and metals; and, finally, astrology, a knowledge of which is indispensable for producing well-timed actions by selecting the most favorable disposition of the stars. Magic is a wisdom that is at the same time speculative and practical, that applies its own body of knowledge to works that are useful to humankind. It can be divided into three types: divine, natural, deceitful and diabolical. Essential both for divine and natural magic is a genuine faith, which requires purity of heart and an intrinsic adherence on the part of the soul to the divinity. Such faith, which renders human beings divine, confers on them the capacity to perform operations on things and transform them according to their own desires (Del senso delle cose, pp. 221–22, 226–29). At the opposite pole to divine magic is the type that is playful and deceitful, thanks to which charlatans skillfully produce effects that stupefy ignorant people. These swindlers cause a leg to burst into flames, though in truth the leg is artificial; they place a nail in their eye and another in their mouth, pretending that it has passed from one to the other; they seem to be pierced by fake daggers and swords; and, using the laws of optics, they make it possible to see distant images.