A treatise concerning the principles of human knowledge -- An essay towards a new theory of vision -- Alciphron, the fourth dialogue (excerpts) -- The theory of vision.

touch 27 Thirrdly, the straining of the eye 28 The occasions which suggest distance have in their own nature no relation to it 29 A difficult case proposed by Dr. Barrow as repugnant to all the known theories 30 This case contradicts a ...

Independently of any eighteenth century work on the geometry of parallels, Thomas Reid discovered the non-euclidean "geometry of visibles" in 1764. Reid's construction uses an idealized eye, incapable of making distance discriminations, to specify operationally a two dimensional visible space and a set of objects, the visibles. Reid offers sample theorems for his doubly elliptical geometry and proposes a natural model, the surface of the sphere. His construction draws on eighteenth century theory of vision for some of its technical features (...) and is motivated by Reid's desire to defend realism against Berkeley's idealist treatment of visual space. (shrink)

The paper provides an account of necessary truths in Berkeley based upon his divine language model. If the thesis of the paper is correct, not all Berkeleian necessary truths can be known a priori.

: Berkeley's Essay Towards a New Theory of Vision presents a theory of various aspects of the spatial content of visual experience that attempts to undercut not only the optico-geometric accounts of e.g., Descartes and Malebranche, but also elements of the empiricist account of Locke. My task in this paper is to shed light on some features of Berkeley's account that have not been adequately appreciated. After rehearsing a more detailed Lockean critique of the notion that depth is a proper (...) object of vision, Berkeley directs arguments he takes to be entirely parallel against the notion that vision has two-dimensional planar contents as proper objects. I show that this argument fails due to an illicit slide unnoticed by both Berkeley and his commentators—a slide present but innocuously so in the case of depth. Berkeley's positive account, according to which the apparent spatial content of vision is a matter of associations between, on the one hand, tactile and motor contents, and on the other hand non-spatial visual contents, also fails because of an illicit slide—again, unnoticed by Berkeley and his commentators. I close by discerning the salvageable and correct core of Berkeley's theory of the spatiality of vision. (shrink)

Berkeley and Helmholtz proposed different indirect mechanisms for size perception: Berkeley, that size was conditioned to various cues, independently of perceived distance; Helmholtz, that it was unconsciously calculated from angular size and perceived distance. The geometrical approach cannot explain size-distance paradoxes (e.g., moon illusion). The dorsal/ventral solution is dubious for close displays and untestable for far displays.

Taking up John of Salisbury’s dictum that we read ancient texts to improve our eyesight, this article returns to an “old” book for “new” insight into the perennial philosophical problem of visual perception. A careful reading of Berkeley’s essay on vision improves our eyesight in at least four ways: First, it reminds us that the most interesting aspects of visual perception are not “primary” but “derivative.” Second, it reminds us that our relationship with the world is an interactive process of (...) making connections and proposes some ways in which those connections and the process of making them might be brought to consciousness and subjected to critical examination. Third, it reminds us of the extent to which making connections is a linguistic process: we live in language as surely as we live in the world, and the processes by which we take our places in the world are forms of language. Fourth, it introduces a concept of “levels” and movement between them that is particularly important to computational models that may result in nonhuman analogues of human vision. (shrink)

Berkeley thinks that we only see the size, shape, location, and orientation of objects in virtue of the correlation between sight and touch. Shadows have all of these spatial properties and yet are intangible. In Seeing Dark Things (2008), Roy Sorensen argues that shadows provide a counterexample to Berkeley's theory of vision and, consequently, to his idealism. This paper shows that Berkeley can accept both that shadows are intangible and that they have spatial properties.