Excepting some hints by Descartes, Malebranche was among the first dimly to anticipate Berkeley, in resolving our supposed power of seeing outness into an interpretation [pg 105] of visual signs which we learn by experience to understand. The most important part of Malebranche's account of seeing is contained in the Recherche de la Vérité (Liv. I. ch. 9), in one of those chapters in which he discusses the frequent fallaciousness of the senses, and in particular of our visual perceptions of extension. He accounts for their inevitable uncertainty by assigning them not to sense but to misinterpretation of what is seen. He also enumerates various visual signs of distance.
That the Recherche of Malebranche, published more than thirty years before the Essay, was familiar to Berkeley before the publication of his New Theory, is proved by internal evidence, and by his juvenile Commonplace Book. I am not able to discover signs of a similar connexion between the New Theory and the chapter on the mystery of sensation in Glanvill's Scepsis Scientifica (ch. 5), published some years before the Recherche of Malebranche, where Glanvill refers to “a secret deduction,” through which—from motions, &c., of which we are immediately percipient—we “spell out” figures, distances, magnitudes, and colours, which have no resemblance to them.
An approach to the New Theory is found in a passage which first appeared in the second edition of Locke's Essay, published in 1694, to which Berkeley refers in his own Essay (sect. 132-35), and which, on account of its relative importance, I shall here transcribe at length:—
“We are further to consider concerning Perception that the ideas we receive by sensation are often, in grown people, altered by the judgment, without our taking notice of it. When we set before our eyes a round globe of any uniform colour, e.g. gold, alabaster, or jet, it is certain that the idea thereby imprinted in our mind is of a flat circle, variously shadowed, with several degrees of light and brightness coming to our eyes. But, we having by use been accustomed to perceive what kind of appearance convex bodies are wont to make in us, what alterations are made [pg 106] in the reflection of light by the difference in the sensible figures of bodies—the judgment presently, by an habitual custom, alters the appearances into their causes; so that, from that which is truly variety of shadow or colour, collecting the figure, it makes it pass for a mark of figure, and frames to itself the perception of a convex figure and an uniform colour, when the idea we receive from them is only a plane variously coloured, as is evident in painting.
“To which purpose I shall here insert a problem of that very ingenious and studious promoter of real knowledge, the learned and worthy Mr. Molyneux, which he was pleased to send me in a letter some months since, and it is this:—Suppose a man born blind, and now adult, and taught by his touch to distinguish between a cube and a sphere of the same metal, and nighly of the same bigness, so as to tell, when he felt the one and the other, which is the cube and which the sphere. Suppose then the cube and the sphere placed on a table, and the blind man be made to see: quere, whether, by his sight, before he touched them, he could not distinguish and tell, which is the globe and which the cube? To which the acute and judicious proposer answers: ‘Not.’ For, though he has obtained the experience of how a globe, how a cube affects his touch; yet he has not obtained the experience that what affects his touch so and so, must affect his sight so and so; so that a protuberant angle in the cube, that pressed his hand unequally, shall appear to his eye as it does in the cube.—I agree with this thinking gentleman, whom I am proud to call my friend, in his answer to this his problem, and am of opinion that the blind man, at first sight, would not be able to say with certainty which was the globe and which the cube, whilst he only saw them; though he would unerringly name them by his touch, and certainly distinguish them by the difference in their figures felt.
“This I have set down, and leave with my reader, as an [pg 107] occasion for him to consider how much he may be beholden to experience, improvement, and acquired notions, where he thinks he had not the least use of, or help from them: and the rather because this observing gentleman further adds that, having, upon the occasion of my book, proposed this problem to divers very ingenious men, he hardly ever met with one that at first gave the answer to it which he thinks true, till by hearing his reasons they were convinced.
“But this is not I think usual in any of our ideas but those received by sight: because sight, the most comprehensive of the senses, conveying to our minds the ideas of light and colours, which are peculiar only to that sense; and also the far different ideas of space, figure, and motion, the several varieties of which change the appearance of its proper object, i.e. light and colours; we bring ourselves by use to judge of the one by the other. This, in many cases, by a settled habit, in things whereof we have frequent experience, is performed so constantly and so quick, that we take that for the perception of our sensation, which is an idea formed by our judgment; so that one, i.e. that of sensation, serves only to excite the other, and is scarce taken notice of itself; as a man who reads or hears with attention and understanding takes little notice of the character or sounds, but of the ideas that are excited in him by them.
“Nor need we wonder that this is done with so little notice, if we consider how very quick the actions of the mind are performed; for, as itself is thought to take up no space, to have no extension, so its actions seem to require no time, but many of them seem to be crowded into an instant. I speak this in comparison of the actions of the body.... Secondly, we shall not be much surprised that this is done with us in so little notice, if we consider how the facility we get of doing things, by a custom of doing, makes them often pass in us without notice. Habits, [pg 108] especially such as are begun very early, come at last to produce actions in us which often escape our observation.... And therefore it is not so strange that our mind should often change the idea of its sensation into that of its judgment, and make the one serve only to excite the other, without our taking notice of it.” (Essay concerning Human Understanding, Book II. ch. 9. § 8.)
This remarkable passage anticipates by implication the view of an interpretation of materials originally given in the visual sense, which, under the name of “suggestion,” is the ruling factor in the New Theory of Vision.
The following sentences relative to the invisibility of distances, contained in the Treatise of Dioptrics (published in 1690) of Locke's friend and correspondent William Molyneux, whose son was Berkeley's pupil, illustrate Locke's statements, and may be compared with the opening sections of the Essay on Vision:—