Sulle orme di Tolomeo: fato e previsione secondo Alberto Magno nel De fato

Probably written in the early 1260s, De fato offers a privileged vantage point from which it is possible to get an insight into Albert the Great’s views on celestial causality and its effects on the terrestrial domain: indeed, while on the one hand the text systematizes the ideas put forward in the Parisian theological works and in the previous commentaries of natural philosophy, on the other hand it heralds the developments of later writings such as the late Summa theologiae. In De fato, Albert gives his investigation a distinctly scientific character, as is evident from the astrological definition of fate that he adopts. Moreover, he shows keen interest in the knowability of fate, reflecting on the legitimacy and status of astrology. Albert’s concern with the nature of the astrological prognostication can be explained in light of the profound influence that Ptolemy’s works exerted upon De fato: from the Quadripartitum and pseudo-Ptolemy’s Centiloquium Albert derives distinctive characteristics of fate (namely, the notions that fate is not compelling; that it lies halfway between the perfection of the celestial spheres and the imperfection of the sublunary matter; and that its influence is received according to the capacity of the inferior beings and can be modified) and key features of astrology (namely, the ideas that astrological predictions have a practical usefulness and a conjectural nature; and that astronomy and astrology are distinct sciences with different subjects and methods). Albert systematically uses Ptolemy’s works, quoting them explicitly or implicitly, and captures their meaning through famous phrases: “per aliud et per accidens”, “homo sapiens dominatur astris”, “elector non nisi probabiliter et communiter iudicare debet”, “forma media est inter necessarium et possibile”, “stellae secundae”.