Il "De substantia orbis" nell’averroismo ebraico (Isaac Albalag, Moshè Narboni, Elia del Medigo)

The Sermo de substantia orbis (Discourse on the Substance of the Celestial Sphere) is an original work by Averroes (1126-1198), no longer extant in Arabic, that has been preserved in Latin and Hebrew translations (the latter with the title Ma’amar be-‘Eṣem ha-Galgal). This work is a collection of treatises dealing with the nature and the properties of the heavens, according to the principles of Aristotelian cosmology. In this paper, I firstly explain the complex history of the text, the subject and the reception of the De substantia orbis in both Latin and Jewish traditions. I then examine the interpretation of this work offered by three renowned Jewish Averroists: Isaac Albalag, Moshe Narboni and Elijah Del Medigo. Finally, I show that Uriel da Costa shares with these thinkers a path of philosophical radicalism, with particular reference to some themes that are crucial in his Examination of Pharisaic Traditions, namely, the doctrine of eternal creation, the necessary order of nature and the resulting negation of miracles.