medieval theories of vision, extramission, Albert the Great, Roger Bacon, Peter Olivi

The history of premodern optics and visual theory is often narrated as a clash between two competing paradigms ? the intromission and the extramission ? we see either by receiving an entity from the outside, or by means of something issuing from our eyes. Although it is sometimes believed that the intromissionist theory developed by Ibn al-Haytham (Alhacen) renders the extramissionist account obsolete, it is worth noting that Medieval Latin scholars still take the extramission quite seriously. The paper investigates three different approaches towards the extramission that were common among the 13th century Latin philosophers ? refutation, syncretism, and reformulation. Four authors are especially examined ? Albert the Great with his thorough refutation of different extramissionist theories; Roger Bacon and his syncretic tendencies to incorporate some extramissionist tenets into a broader intromissionist framework; the anonymous author of the Summa philosophiae (once ascribed to Robert Grosseteste) suggesting that the extramission postulate describes rather the dynamics of our visual power; and, finally, Peter Olivi with his full-fledged reformulation of the extramission and his understanding of the (visual) attention as a ?virtual ray?. The paper thus argues that the extramission was not conceived as an antiquated theory by the 13th century thinkers, but it was carefully examined or even ? in some cases ? rethought and elaborated in an original way.