It has long been noted that towards the end of the sixteenth century the Catholic Church began to use its instruments of censorship – the Inquisition and the Index of Forbidden Books – to prosecute magic with increased vigour. These developments are often deemed to have had important consequences for the development of modern science in Italy, for they delimited areas of legitimate investigation of the natural world. Previous accounts of the censorship of magic have tended to suggest that the (...) Church as an institution was opposed to, and sought to eradicate, the practice of magic. I do not seek to contest the fact that ecclesiastical censors prosecuted various magical and divinatory practices with greater enthusiasm at this time, but I suggest that in order to understand this development more fully it is necessary to offer a more complex picture of the Church. In this article I use the case of the Neapolitan magus Giambattista Della Porta to argue that during the course of the century the acceptable boundaries of magical speculation became increasingly clearly defined. Consequently, many practices and techniques that had previously been of contested orthodoxy were categorically defined as heterodox and therefore liable to prosecution and censorship. I argue, however, that this development was not driven by the Church asserting a ‘traditional’ hostility towards magic, but was instead the result of one particular faction within the Church embedding their conception of orthodox philosophical investigation of the natural world within the machinery of censorship. (shrink)