Guillermo Willis (Warburg Institute)
Pierre Gassendi and monocular vision

In 1637, the French philosopher Pierre Gassendi (1592–1655) sought to console Galileo Galilei, who had recently lost sight in one eye, by proposing an unconventional idea: that distinct visual perception arises solely from the retinal image of a single eye. Between the 1630s and 1650s, Gassendi drew upon Epicurus’s theory of matter to erect a natural philosophical framework that explained sensorial qualities only in terms of atoms and the void. This presentation delves into Gassendi’s account of the causes of our perception of two visual qualities, magnitude and distance, as affected by monocular vision. I examine two of his propositions: first, that the left and right eyes possess dissimilar powers in the apprehension of visual species; and second, contrary to conventional knowledge, that the visual axes of both eyes run parallel through the visual field rather than converging at a focal point.

By analysing Gassendi’s correspondence with Galileo Galilei and Fortunio Liceti, along with the portrayal of visual qualities that the French philosopher delivered in his later works, this talk explores the humanistic foundations of these stances on monocular vision and explains their significance towards validating visual perception in the seventeenth century, amidst the epistemological challenges resulting from the contemporary astronomical advances and the emergence of Cartesian optics.