In other parts of Hartley’s book (e.g. Prop. 58) the relation of our visual judgments of magnitude, figure, motion, distance, and position to the laws of association is explained, and the associating circumstances by which these judgments are formed are enumerated in detail. Dr. Porterfield of Edinburgh, in his _Treatise on the Eye, or the Manner and Phenomena of Vision_ (Edinburgh, 1759), is an exception to the consent which the doctrine had then widely secured. He maintains, in opposition to Berkeley, that “the judgments we form of the situation and distance of visible objects, depend not on custom and experience, but on original instinct, to which mind is subject in our embodied state(279).” Berkeley’s Theory of Vision, in so far as it resolves our visual perceptions of distance into interpretation of arbitrary signs, received the qualified approbation of Reid, in his _Inquiry into the Human Mind on the Principles of Common Sense_ (1764). He criticises it in the _Inquiry_, where the doctrine of visual signs, of which Berkeley’s whole philosophy is a development, is accepted, and to some extent applied. With Reid it is divorced, however, from the Berkeleian conception of the material world, although the Theory of Vision was the seminal principle of Berkeley’s Theory of Matter(280). This Theory of Matter was imperfectly conceived and then rejected by Reid and his followers, while the New Theory of Vision obtained the general consent of the Scottish metaphysicians. Adam Smith refers to it in his _Essays_ (published in 1795) as “one of the finest examples of philosophical analysis that is to be found either in our own or in any other language.” Dugald Stewart characterises it in his _Elements_ as “one of the most beautiful, and at the same time one of the most important theories of modern philosophy.” “The solid additions,” he afterwards remarks in his _Dissertation_, “made by Berkeley to the stock of human knowledge, were important and brilliant. Among these the first place is unquestionably due to his _New Theory of Vision_, a work abounding with ideas so different from those commonly received, and at the same time so profound and refined, that it was regarded by all but a few accustomed to deep metaphysical reflection, rather in the light of a philosophical romance than of a sober inquiry after truth. Such, however, has since been the progress and diffusion of this sort of knowledge, that the leading and most abstracted doctrines contained in it form now an essential part of every elementary treatise on optics, and are adopted by the most superficial smatterers in science as fundamental articles of their faith.” The _New Theory_ is accepted by Thomas Brown, who proposes (_Lectures_, 29) to extend the scope of its reasonings. With regard to perceptions of sight, Young, in his _Lectures on Intellectual Philosophy_ (p. 102), says that “it has been universally admitted, at least since the days of