Reid and Wells on Single and Double Vision

Abstract

In a recent article on Reid’s theory of single and double vision, James Van Cleve considers an argument against direct realism formulated by Hume.1 In the Treatise of Human Nature, Hume argues for the mind-dependent nature of the objects of our perception from the phenomenon of double vision. As Hume says, ‘[w]hen we press one eye with a finger, we immediately perceive all the objects to become double, and one half of them to be remov’d from their common and natural position.’2 Since we cannot ascribe continued existence to either of these objects, they must both be mind-dependent. Reid does not address this particular argument, but Van Cleve considers possible answers Reid might have given to Hume. He finds some fault with all the answers he considers. In what follows, I will first present Van Cleve’s reconstruction of Hume’s argument. I will then suggest that both appearances in double vision could be considered visible figures of the object, and show how this solution might preserve Reid’s direct realism. However, this solution is not compatible with the single appearance of an object predicted by Reid’s theory of single and double vision. This consequence will appear evident, once we consider the critique of Reid’s theory of single and double vision formulated by William Charles Wells (1757 – 1817) in his Essay upon Single Vision with Two Eyes (1792).3