Voltaire and Condillac gave currency to the New Theory in France, and it soon became a commonplace with D'Alembert, Diderot, Buffon, and other French philosophers. In Germany we have allusions to it in the Berlin Memoirs and elsewhere; but, although known by name, if not in its distinctive principle and latent idealism, it has not obtained [pg 112] the consideration which its author's developed theory of the material as well as the visible world has received. The Kantian a priori criticism of our cognition of Space, and of our mathematical notions, subsequently indisposed the German mind to the a posteriori reasoning of Berkeley's Essay.
Its influence is apparent in British philosophy. The following passages in Hartley's Observations on Man, published in 1749, illustrate the extent to which some of the distinctive parts of the new doctrine were at that time received by an eminent English psychologist:—
“Distance is judged of by the quantity of motion, and figure by the relative quantity of distance.... And, as the sense of sight is much more extensive and expedite than feeling, we judge of tangible qualities chiefly by sight, which therefore may be considered, agreeably to Bishop Berkeley's remark, as a philosophical language for the ideas of feeling; being, for the most part, an adequate representative of them, and a language common to all mankind, and in which they all agree very nearly, after a moderate degree of experience.
“However, if the informations from touch and sight disagree at any time, we are always to depend upon touch, as that which, according to the usual ways of speaking upon these subjects, is the true representation of the essential properties, i.e. as the earnest and presage of what other tangible impressions the body under consideration will make upon our feeling in other circumstances; also what changes it will produce in other bodies; of which again we are to determine by our feeling, if the visual language should not happen to correspond to it exactly. And it is from this difference that we call the touch the reality, light the representative—also that a person born blind may foretell with certainty, from his present tangible impressions, what others would follow upon varying the circumstances; whereas, if we could suppose a person to be born without [pg 113] feeling, and to arrive at man's estate, he could not, from his present visible impressions, judge what others would follow upon varying the circumstances. Thus the picture of a knife, drawn so well as to deceive his eye, would not, when applied to another body, produce the same change of visible impressions as a real knife does, when it separates the parts of the body through which it passes. But the touch is not liable to these deceptions. As it is therefore the fundamental source of information in respect of the essential properties of matter, it may be considered as our first and principal key to the knowledge of the external world.” (Prop. 30.)
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, [pg 114] 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 Berkeley, that many of those which appear to us at present to be instantaneous and primitive, can yet be shewn to be [pg 115] acquired; that most of the adult perceptions of sight are founded on the previous information of touch; that colour can give us no conception originally of those qualities of bodies which produce it in us; and that primary vision gives us no notion of distance, and, as I believe, no notion of magnitude.” Sir James Mackintosh, in his Dissertation, characterises the New Theory of Vision as “a great discovery in Mental Philosophy.” “Nothing in the compass of inductive reasoning,” remarks Sir William Hamilton (Reid's Works, p. 182, note), “appears more satisfactory than Berkeley's demonstration of the necessity and manner of our learning, by a slow process of observation and comparison alone, the connexion between the perceptions of vision and touch, and, in general, all that relates to the distance and magnitude of external things[281].”
The New Theory of Vision has in short been generally accepted, so far as it was understood, alike by the followers of Hartley and by the associates and successors of Reid. Among British psychologists, it has recommended itself to rationalists and sensationalists, to the advocates of innate principles, and to those who would explain by accidental association what their opponents attribute to reason originally latent in man. But this wide conscious assent is I think chiefly confined to the proposition that distance is invisible, and hardly reaches the deeper implicates of the theory, on its extension to all the senses, leading to a perception of the final unity [pg 116] of the natural and the supernatural, and the ultimate spirituality of the universe[282].