This article seeks the origin, in the theories of Ibn al-Haytham (Alhazen), Descartes, and Berkeley, of two-stage theories of spatial perception, which hold that visual perception involves both an immediate representation of the proximal stimulus in a two-dimensional ‘‘sensory core’’ and also a subsequent perception of the three dimensional world. The works of Ibn al-Haytham, Descartes, and Berkeley already frame the major theoretical options that guided visual theory into the twentieth century. The field of visual perception was the first area (...) of what we now call psychology to apply mathematics, through geometrical models as used by Euclid, Ptolemy, Ibn al-Haytham, and Descartes (among others). The article shows that Kepler’s discovery of the retinal image, which revolutionized visual anatomy and entailed fundamental changes in visual physiology, did not alter the basic structure of theories of spatial vision. These changes in visual physiology are advanced especially in Descartes' Dioptrics and his L'Homme. Berkeley develops a radically empirist theory vision, according to which visual perception of depth is learned through associative processes that rely on the sense of touch. But Descartes and Berkeley share the assertion that there is a two-dimensional sensory core that is in principle available to consciousness. They also share the observation that we don't usually perceived this core, but find depth and distance to be phenomenally immediate, a point they struggle to accommodate theoretically. If our interpretation is correct, it was not a change in the theory of the psychology of vision that engendered the idea of a sensory core, but rather the introduction of the theory into a new metaphysical context. (shrink)

Ce recueil presente la majeure partie des etudes consacrees par Pierre Costabel a l'oeuvre de Descartes, jusqu'alors dispersees dans des publications diverses. Le titre sous lequel elles se trouvent rassemblees n'est nullement factice, car c'est bien l'originalite de Descartes savant qui a constitue un objet de recherche pour Pierre Costabel, et le pluriel figurant dans ce titre indique que, durant quelque vingt-cinq ans, cette etude a porte sur divers aspects de Descartes savant, sans pretendre apporter davantage que des suggestions quant (...) a une synthese. Si les articles rassembles ici etudient dans le detail les textes scientifiques de Descartes et prennent en consideration la grande diversite des disciplines abordees par le savant, ils renoncent a une approche exhaustive ou systematique: c'est avant tout a l'audace de la pensee cartesienne que Pierre Costabel rend hommage. (shrink)

Mariotte's discovery of the blind spot is often quoted, but his contribution to the physiology of vision is generally underestimated. Surprised by the result of his fundamental experiment, Mariotte abandoned his starting hypothesis on the physiological role of the retina and came to the conclusion that the site of vision is the 'choroid'. This was the name not only for the choroid layer in the modern sense but also for the pigmentated part of the retina, where Mariotte localized the seat (...) of vision. Mariotte's 'heretical' assertion provoked an important public controversy with the anatomists Pecquet and Perrault. This debate is often misrepresented by historians, who, considering Mariotte's opinion basically mistaken, failed to enter into the details. Mariotte was the very first to measure the size of the unseen area in the visual field and to determine the corresponding optic disk on the fundus oculi. He proved that the central scotoma is not due to the vascular trunk, discovered the peripheric angioscotomas, explained the imperceptibility of the blind spot under ordinary conditions of binocular and monocular vision, posed the problem of filling-in, observed the phenomenon later known as staring-blindness and advanced a dioptric explanation of the luminous eye in some animals. The debate between Mariotte, Pecquet and Perrault is particularly instructive for the philosophy of science as an example of the intertwining of experimental reasoning and scholastic argumentation. (shrink)