Una quintuplice sfera : sulla seconda lezione oxoniense di Giordano Bruno

In this paper we first attempt to reconstruct the discussion about Bruno's second lecture at Oxford University in the summer of 1583. Next, we propose the reading of a passage of Insomnium (Paris 1586), in which a ‘vision' of the astronomical system is outlined, similar to what Bruno himself would describe a few years later in Articuli adversus mathematicos (1588) and then in De immenso (1591), and which has never been read by the critics in an astronomical sense. Starting from this brief account, we try to show how shortly after the publication of the Italian dialogues, Bruno already had in mind an idea of the ‘solar system' based on the centrality of the Sun and only four surrounding ‘orbits'. Although much time has passed since the Oxonian lectures, it is worth noting that the Insomnium system (more explicitly) and those proposed in the following texts presuppose a system formed by five ‘spheres', just like the title Bruno himself gave to that lecture. [Publisher's text]