Averroes' De Substantia orbis: Critical Edition of the Hebrew Text with English Translation and Commentary

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At the end of the sixteenth century new anatomical knowledge led both empirically minded philosophers and philosophically minded anatomists to rethink theories of light, color, and vision in subtle but significant ways. In this paper I show how anatomy and philosophy conspired to understand the structure and the purpose of the parts of the eye in two important, but largely overlooked, works by professors at the University of Padua: the natural philosopher Jacopo Zabarella’s De visu (first published in 1590) and the anatomist and physician Hieronymus Fabricius ab Aquapendente’s De visione (1600). How they understood the roles of the various parts of the eye reveals much about the strategies different disciplines used to reconcile ancient authorities (particularly Galen and Aristotle) with new anatomical observations and experiments. Importantly, the two professors offer identical accounts of the size, shape, and clarity, as well as the usus (or Galeno-Aristotelian final cause), of the vitreous humor, the transparent gel that fills the space between the crystalline humor (or lens) and the retina. This account of the vitreous is at the center of a theory of vision that differs in crucial ways from previous perspectivists, natural philosophers, and anatomists. Given this striking similarity, I argue that the two must have interacted significantly at Padua. I also argue that (by way of a former student of Fabricius, the anatomist and physician Jan Jessenius) this theory of vision influenced Kepler’s revolutionary account in his Ad Vitellionem paralipomena (1604) in certain respects.
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How do the variegated forms of sublunar substances (the elements, homoeomerous substances, plants, animals) arise in prime matter? Averroes throughout his life believed that “a principle from without” was involved, but changed his mind over its identity. While in an early period of his life he maintained that all forms emanate from the active intellect, he later discarded that metaphysical notion and sought to develop a more naturalistic, astrologically inspired account, which identified the heavenly bodies as the source of sublunar forms. Comparing different versions of Averroean texts, this paper seeks to spell out how, in Averroes' view, the heavenly bodies generate forms in matter. Averroes claims that this is brought about by means of their “heats,” an answer that is however problematic seeing that in the Aristotelian cosmology the celestial realm is quality-less. The paper examines Averroes' ideas on the relationship between light and heat, concluding that the Commentator was unable to integrate the postulate that the heavenly bodies inform matter within his Aristotelian theory of matter.
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