Berkeley's "new theory of vision" and, In particular, His sensationalist solution to the problem of judging distance and magnitude were discussed by many eighteenth-Century authors who faced a variety of problem situations. More specifically, Berkeley's theory fed into the debate over whether the phenomena of vision were susceptible to mathematical analysis or were experientially determined. In this paper a variety of responses to berkeley are examined, Concluding with thomas reid's attempt to distinguish physical optics (which can be analyzed geometrically) from (...) the psychology of vision (in which experience plays a major role). (shrink)

An explication is offered of Reid’s claim (discussed recently by Yaffe and others) that the geometry of the visual field is spherical geometry. It is shown that the sphere is the only surface whose geometry coincides, in a certain strong sense, with the geometry of visibles.

In his 'Inquiry', Reid claims, against Berkeley, that there is a science of the perspectival shapes of objects ('visible figures'): they are geometrically equivalent to shapes projected onto the surfaces of spheres. This claim should be understood as asserting that for every theorem regarding visible figures there is a corresponding theorem regarding spherical projections; the proof of the theorem regarding spherical projections can be used to construct a proof of the theorem regarding visible figures, and vice versa. I reconstruct Reid's (...) argument for this claim, and expose its mathematical underpinnings: it is successful, and depends on no empirical assumptions to which he was not entitled about the workings of the human eye. I also argue that, although Reid may or may not have been aware of it, the geometry of spherical projections is not the only geometry of visible figure. (shrink)

In a brief but remarkable section of the Inquiry into the Human Mind, Thomas Reid argued that the visual field is governed by principles other than the familiar theorems of Euclid—theorems we would nowadays classify as Riemannian. On the strength of this section, he has been credited by Norman Daniels, R. B. Angell, and others with discovering non-Euclidean geometry over half a century before the mathematicians—sixty years before Lobachevsky and ninety years before Riemann. I believe that Reid does indeed have (...) a fair claim to have discovered a non-Euclidean geometry. However, the real basis of Reid’s geometry of visibles is subtle and easy to misidentify. My main aim in what follows is to make clear what the real basis is, separating it from several fallacious or irrelevant considerations on which Reid may seem to be relying. A secondary aim is to air the worry that Reid’s case for his geometry can succeed only at the cost of compromising the achievement for which Reid is best known—his direct realist theory of perception. (shrink)

The subject of this investigation is the role of conventions in the formulation of Thomas Reid’s theory of the geometry of vision, which he calls the ‘geometry of visibles’. In particular, we will examine the work of N. Daniels and R. Angell who have alleged that, respectively, Reid’s ‘geometry of visibles’ and the geometry of the visual field are non-Euclidean. As will be demonstrated, however, the construction of any geometry of vision is subject to a choice of conventions regarding the (...) construction and assignment of its various properties, especially metric properties, and this fact undermines the claim for a unique non-Euclidean status for the geometry of vision. Finally, a suggestion is offered for trying to reconcile Reid’s direct realist theory of perception with his geometry of visibles.While Thomas Reid is well-known as the leading exponent of the Scottish ‘common-sense’ school of philosophy, his role in the history of geometry has only recently been drawing the attention of the scholarly community. In particular, several influential works, by N. Daniels and R. B. Angell, have claimed Reid as the discoverer of non-Euclidean geometry; an achievement, moreover, that pre-dates the geometries of Lobachevsky, Bolyai, and Gauss by over a half century. Reid’s alleged discovery appears within the context of his analysis of the geometry of the visual field, which he dubs the ‘geometry of visibles’. In summarizing the importance of Reid’s philosophy in this area, Daniels is led to conclude that ‘there can remain little doubt that Reid intends the geometry of visibles to be an alternative to Euclidean geometry’;1 while Angell, similarly inspired by Reid, draws a much stronger inference: ‘The geometry which precisely and naturally fits the actual configurations of the visual field is a non-Euclidean, two-dimensional, elliptical geometry. In substance, this thesis was advanced by Thomas Reid in 1764...’, 2 The significance of these findings has not gone unnoticed in mathematical and scientific circles, moreover, for Reid’s name is beginning to appear more frequently in historical surveys of the development of geometry and the theories of space., 3Implicit in the recent work on Reid’s ‘geometry of visibles’, or GOV, one can discern two closely related but distinct arguments: first, that Reid did in fact formulate a non-Euclidean geometry, and second, that the GOV is non-Euclidean. This essay will investigate mainly the latter claim, although a lengthy discussion will be accorded to the first. Overall, in contrast to the optimistic reports of a non-Euclidean GOV, it will be argued that there is a great deal of conceptual freedom in the construction of any geometry pertaining to the visual field. Rather than single out a non-Euclidean structure as the only geometry consistent with visual phenomena, an examination of Reid, Daniels, and Angell will reveal the crucial role of geometric ‘conventions’, especially of the metric sort, in the formulation of the GOV. Consequently, while a non-Euclidean geometry is consistent with Reid’s GOV, it is only one of many different geometrical structures that a GOV can possess. Angell’s theory that the GOV can only be construed as non-Euclidean, is thus incorrect. After an exploration of Reid’s theory and the alleged non-Euclidean nature of the GOV, in 1 and 2 respectively, the focus will turn to the tacit role of conventionalism in Daniels’ reconstruction of Reid’s GOV argument, and in the contemporary treatment of a non-Euclidean visual geometry offered by Angell. Finally, in the conclusion, a suggestion will be offered for a possible reconstruction of Reid’s GOV that does not violate his avowed ‘direct realist’ theory of perception, since this epistemological thesis largely prompted his formulation of the GOV. (shrink)

We can make a good prima facie case for the inconsistency of Reid's theory of perception with his rejection of the Ideal Theory. Most scholars believe Reid adopts a theory on which the immediate object of perception is a physical body. Reid is thought to do this in order to avoid problems generated by the veil of perception in the Ideal Theory, a conjunction of commitments Reid closely associates with Hume and Locke. Reid explains that the Ideal Theory "leans with (...) its whole weight upon a hypothesis...[t]hat nothing is perceived but what is in the mind which perceives it". Reid attributes to the Ideal Theory thesis. (shrink)

We cannot imagine two straight lines intersecting at two points even though they may do so. In this case our abilities to imagine depend upon our abilities to visualise.

Reid's Inquiry into the Human Mind on the Principles of Common Sense devotes more space to double vision than to any other topic. In what follows, I examine why this subject was so important to Reid and why he dealt with it as he did. I also consider whether his argument for his position begs the question against his main opponents, Berkeley and Robert Smith. I show that, as Reid presented it, it does, but that he could have said more (...) than he did in reply to Smith. My discussion of why double vision was important for Reid begins with an exposition of the relevance of the theory of vision for one of Reid's principal concerns in the Inquiry: the concern to respond to scepticism concerning our knowledge of an external world. I then turn to consider how Reid's account of double vision contributes to his epistemological realism and why the alternative account offered by Berkeley and Smith challenges it. (shrink)

(Originally published in _Reid Studies_ 4 (2000-01): 35-51.) Reid and Berkeley disagreed over whether we directly perceive objects located outside of us in a surrounding space, commonly revealed by both vision and touch. Berkeley considered a successful account of erect vision to be crucial for deciding this dispute, at one point calling it ‘the principal point in the whole optic theory.’ Reid's critique of Berkeley's position on this topic is very brief, and appears to miss Berkeley's point. I argue that (...) there is more to Reid's response to Berkeley than at first meets the eye. Reid's rival account of erect vision draws on evidence that makes a compelling case for the position that we see the same space that we touch. (shrink)

This paper contrasts three different positions taken by 18th century British scholars on how sensations, particularly sensations of colour and touch, come to be localized in space: Berkeley’s view that we learn to localize ideas of colour by associating certain purely qualitative features of those ideas with ideas of touch and motion, Hume’s view that visual and tangible impressions are originally disposed in space, and Reid’s view that we are innately disposed to refer appearances of colour to the end of (...) a line passing through the centre of the eye and originating from the spot on the back of the retina where the material impression causing that appearance was received. Reid’s reasons for rejecting the Berkeleian and Humean views are examined. It is argued that Reid’s position on visual localization is ultimately driven by his dualistic metaphysical commitments rather than by an empirically grounded investigation of the phenomena of vision. To this extent, his position sits uncomfortably with his own methodological commitments. (shrink)

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 ...

In the chapter “The Geometry of Visibles” in his ‘Inquiry into the Human Mind’, Thomas Reid constructs a special space, develops a special geometry for that space, and offers a natural model for this geometry. In doing so, Reid “discovers” non-Euclidean Geometry sixty years before the mathematicians. This paper examines this “discovery” and the philosophical motivations underlying it. By reviewing Reid’s ideas on visible space and confronting him with Kant and Berkeley, I hope, moreover, to resolve an alleged impasse in (...) Reid’s philosophy concerning the contradictory characteristics of Reid’s tangible and visible space. (shrink)

(This article was republished in lightly re-edited form in _Journal of Scottish Philosophy_ 16 (2018) 175-91.) Reid and Berkeley disagreed over whether we directly perceive objects located outside of us in a surrounding space, commonly revealed by both vision and touch. Berkeley considered a successful account of erect vision to be crucial for deciding this dispute, at one point calling it ‘the principal point in the whole optic theory.’ Reid's critique of Berkeley's position on this topic is very brief, and (...) appears to miss Berkeley's point. I argue that there is more to Reid's response to Berkeley than at first meets the eye. Reid's rival account of erect vision draws on evidence that makes a compelling case for the position that we see the same space that we touch. (shrink)