The Works of George Berkeley Part 28

The closing sections (149-60), as I have said, are supplementary, and profess to determine the sort of extension-visible or tangible-with which Geometry is concerned. In concluding that it is tangible, he tries to picture the mental state of Idominians, or unbodied spirits, endowed with visual perceptions _only_, and asks what _their_ conception of outness and solid extension must be. Here further refinements in the interpretation of visual perception, and its organic conditions, which have not escaped the attention of latter psychologists and biologists, are hinted at.

Whether the data of sight consist of non-resembling arbitrary Signs of the tactual distances, sizes, and situations of things, is a question which some might prefer to deal with experimentally-by trial of the experience of persons in circ.u.mstances fitted to supply an answer. Of this sort would be the experience of the born-blind, immediately after their sight has been restored; the conception of extension and its relations found in persons who continue from birth unable to see; the experience (if it could be got) of persons always dest.i.tute of all tactual and locomotive perceptions, but familiar with vision; and the facts of seeing observed in infants of the human species, and in the lower animals.

Berkeley did not try to verify his conclusions in this way. Here and there (sect. 41, 42, 79, 92-99, 103, 106, 110, 128, 132-37), he conjectures what the first visual experience of those rescued from born-blindness is likely to be; he also speculates, as we have seen, about the experience of unbodied spirits supposed to be able to see, but unable to touch or move (sect. 153-59); and in the Appendix he refers, in confirmation of his New Theory, to a reported case of one born blind who had obtained sight. But he forms his Theory independently of those delicate and difficult investigations. His testing facts were sought introspectively. Indeed those physiologists and mental philosophers who have since tried to determine what vision in its purity is, by cases either of communicated sight or of continued born-blindness, have ill.u.s.trated the truth of Diderot's remark-"preparer et interroger un aveugle-ne n'eut point ete une occupation indigne des talens reunis de Newton, Des Cartes, Locke, et Leibniz(275)."

Berkeley's _New Theory_ has been quoted as a signal example of discovery in metaphysics. The subtle a.n.a.lysis which distinguishes _seeing_ strictly so called, from judgments about extended things, suggested by what we see, appears to have been imperfectly known to the ancient philosophers.

Aristotle, indeed, speaks of colour as the only proper object of sight; but, in pa.s.sages of the _De Anima_(276) where he names properties peculiar to particular senses, he enumerates others, such as motion, figure, and magnitude, which belong to all the senses in common. His distinction of Proper and Common Sensibles appears at first to contradict Berkeley's doctrine of the heterogeneity of the ideal visible and the real tangible worlds. Aristotle, however, seems to question the immediate perceptibility of Common Sensibles, and to regard them as realised through the activity of intelligence(277).

Some writers in Optics, in mediaeval times, and in early modern philosophy, advanced beyond Aristotle, in explaining the relation of our matured notion of distance to what we originally perceive in seeing, and in the fifteenth century it was discovered by Maurolyco that the rays of light from the object converge to a focus in the eye; but I have not been able to trace even the germ of the _New Theory_ in these speculations.

Excepting some hints by Descartes, Malebranche was among the first dimly to antic.i.p.ate Berkeley, in resolving our supposed power of seeing outness into an interpretation 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 Verite_ (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 a.s.signing 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 pa.s.sage 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 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 pa.s.s 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 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 s.p.a.ce, 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 s.p.a.ce, 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 pa.s.s in us without notice. Habits, 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 pa.s.sage antic.i.p.ates 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, ill.u.s.trate Locke's statements, and may be compared with the opening sections of the _Essay on Vision_:-

"In plain vision the estimate we make of the distance of objects (especially when so far removed that the interval between our two eyes bears no sensible proportion thereto, or when looked upon with one eye only) is rather the act of our judgment than of sense; and acquired by exercise, and a faculty of comparing, rather than natural. For, distance of itself is not to be perceived; for, 'tis a line (or a length) presented to our eye with its end toward us, which must therefore be only a point, and that is invisible. Wherefore distance is chiefly perceived by means of interjacent bodies, as by the earth, mountains, hills, fields, trees, houses, &c. Or by the estimate we make of the comparative magnitude of bodies, or of their faint colours, &c. These I say are the chief means of apprehending the distance of objects that are considerably remote. But as to nigh objects-to whose distance the interval of the eyes bears a sensible proportion-their distance is perceived by the turn of the eyes, or by the angle of the optic axes (_Gregorii Opt. Promot._ prop. 28). This was the opinion of the ancients, Alhazen, Vitellio, &c. And though the ingenious Jesuit Tacquet (_Opt. Lib. I._ prop. 2) disapprove thereof, and objects against it a new notion of Ga.s.sendus (of a man's seeing only with one eye at a time one and the same object), yet this notion of Ga.s.sendus being absolutely false (as I could demonstrate were it not beside my present purpose), it makes nothing against this opinion.

"Wherefore, distance being only a line and not of itself perceivable, if an object were conveyed to the eye by one single ray only, there were no other means of judging of its distance but by some of those hinted before.

Therefore when we estimate the distance of nigh objects, either we take the help of both eyes; or else we consider the pupil of one eye as having breadth, and receiving a parcel of rays from each radiating point. And, according to the various inclinations of the rays from one point on the various parts of the pupil, we make our estimate of the distance of the object. And therefore (as is said before), by one single eye we can only judge of the distance of such objects to whose distance the breadth of the pupil has a sensible proportion.... For, it is observed before (prop. 29, sec. 2, see also _Gregorii Opt. Promot._ prop. 29) that for viewing objects remote and nigh, there are requisite various conformations of the eye-the rays from nigh objects that fall on the eye diverging more than those from more remote objects." (_Treatise of Dioptrics_, Part I. prop.

31.)

All this helps to shew the state of science regarding vision about the time Berkeley's _Essay_ appeared, especially among those with whose works he was familiar(278). I shall next refer to ill.u.s.trations of the change which the _Essay_ produced.

The _New Theory_ has occasioned some interesting criticism since its appearance in 1709. At first it drew little attention. For twenty years after its publication the allusions to it were few. The account of Cheselden's experiment upon one born blind, published in 1728, in the _Philosophical Transactions_, which seemed to bring the Theory to the test of scientific experiment, recalled attention to Berkeley's reasonings. The state of religious thought about the same time confirmed the tendency to discuss a doctrine which represented human vision as interpretation of a natural yet divine language, thus suggesting Omnipresent Mind.

Occasional discussions of the _New Theory_ may be found in the _Gentleman's Magazine_, from 1732 till Berkeley's death in 1753. Some criticisms may also be found in Smith's _Optics_, published in 1738.

Essential parts of Berkeley's a.n.a.lysis are explained by Voltaire, in his _elemens de la Philosophie de Newton_. The following from that work is here given on its own account, and also as a prominent recognition of the new doctrine in France, within thirty years from its first promulgation:-

"Il faut absolument conclure de tout ceci, que les distances, les grandeurs, les situations, ne sont pas, a proprement parler, des choses visibles, c'est-a-dire, ne sont pas les objets propres et immediats de la vue. L'objet propre et immediat de la vue n'est autre chose que la lumiere coloree: tout le reste, nous ne le sentons qu'a la longue et par experience. Nous apprenons a voir precis.e.m.e.nt comme nous apprenons a parler et a lire. La difference est, que l'art de voir est plus facile, et que la nature est egalement a tous notre maitre.

"Les jugements soudains, presque uniformes, que toutes nos ames, a un certain age, portent des distances, des grandeurs, des situations, nous font penser qu'il n'y a qu'a ouvrir les yeux pour voir la maniere dont nous voyons. On se trompe; il y faut le secours des autres sens. Si les hommes n'avaient que le sens de la vue, ils n'auraient aucun moyen pour connaitre l'etendue en longueur, largeur et profondeur; et un pur esprit ne la connaitrait pas peutetre, a moins que Dieu ne la lui revelat. Il est tres difficile de separer dans notre entendement l'extension d'un objet d'avec les couleurs de cet objet. Nous ne voyons jamais rien que d'etendu, et de la nous sommes tous portes a croire que nous voyons en effet l'etendue." (_elemens de la Philos. de Newton_, Seconde Partie, ch. 7.)

Condillac, in his _Essais sur l'Origine des Connaissances Humaines_ (Part I. sect. 6), published in 1746, combats Berkeley's _New Theory_, and maintains that an extension exterior to the eye is immediately discernible by sight; the eye being naturally capable of judging at once of figures, magnitudes, situations, and distances. His reasonings in support of this "prejudice," as he afterwards allowed it to be, may be found in the section ent.i.tled "De quelques jugemens qu'on a attribues a l'ame sans fondement, ou solution d'un probleme de metaphysique." Here Locke, Molyneux, Berkeley, and Voltaire are criticised, and Cheselden's experiment is referred to. Condillac's subsequent recantation is contained in his _Traite des Sensations_, published in 1754, and in his _L'Art de Penser_. In the _Traite des Sensations_ (Troisieme Partie, ch. 3, 4, 5, 6, 7, 8, &c.) the whole question is discussed at length, and Condillac vindicates what he allows must appear a marvellous paradox to the uninitiated-that we only gradually learn to see, hear, smell, taste, and touch. He argues in particular that the eye cannot originally perceive an extension that is beyond itself, and that perception of trinal s.p.a.ce is due to what we experience in touch.

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 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 s.p.a.ce, 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 pa.s.sages in Hartley's _Observations on Man_, published in 1749, ill.u.s.trate 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 quant.i.ty of motion, and figure by the relative quant.i.ty 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 circ.u.mstances; 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 circ.u.mstances; whereas, if we could suppose a person to be born without feeling, and to arrive at man's estate, he could not, from his present visible impressions, judge what others would follow upon varying the circ.u.mstances. 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 pa.s.ses. 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 princ.i.p.al 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 a.s.sociation is explained, and the a.s.sociating circ.u.mstances 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 a.n.a.lysis 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 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 compa.s.s 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 a.s.sociates 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 a.s.sociation what their opponents attribute to reason originally latent in man. But this wide conscious a.s.sent 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 of the natural and the supernatural, and the ultimate spirituality of the universe(282).

Dedication

TO THE RT. HON. SIR JOHN PERCIVALE, BART.(283),

ONE OF HER MAJESTY'S MOST HONOURABLE PRIVY COUNCIL

IN THE KINGDOM OF IRELAND.

Sir,

I could not, without doing violence to myself, forbear upon this occasion to give some public testimony of the great and well-grounded esteem I have conceived for you, ever since I had the honour and happiness of your acquaintance. The outward advantages of fortune, and the early honours with which you are adorned, together with the reputation you are known to have amongst the best and most considerable men, may well imprint veneration and esteem on the minds of those who behold you from a distance. But these are not the chief motives that inspire me with the respect I bear you. A nearer approach has given me the view of something in your person infinitely beyond the external ornaments of honour and estate. I mean, an intrinsic stock of virtue and good sense, a true concern for religion, and disinterested love of your country. Add to these an uncommon proficiency in the best and most useful parts of knowledge; together with (what in my mind is a perfection of the first rank) a surpa.s.sing goodness of nature. All which I have collected, not from the uncertain reports of fame, but from my own experience. Within these few months that I have the honour to be known unto you, the many delightful hours I have pa.s.sed in your agreeable and improving conversation have afforded me the opportunity of discovering in you many excellent qualities, which at once fill me with admiration and esteem. That one at those years, and in those circ.u.mstances of wealth and greatness, should continue proof against the charms of luxury and those criminal pleasures so fashionable and predominant in the age we live in; that he should preserve a sweet and modest behaviour, free from that insolent and a.s.suming air so familiar to those who are placed above the ordinary rank of men; that he should manage a great fortune with that prudence and inspection, and at the same time expend it with that generosity and n.o.bleness of mind, as to shew himself equally remote from a sordid parsimony and a lavish inconsiderate profusion of the good things he is intrusted with-this, surely, were admirable and praiseworthy. But, that he should, moreover, by an impartial exercise of his reason, and constant perusal of the sacred Scriptures, endeavour to attain a right notion of the principles of natural and revealed religion; that he should with the concern of a true patriot have the interest of the public at heart, and omit no means of informing himself what may be prejudicial or advantageous to his country, in order to prevent the one and promote the other; in fine, that, by a constant application to the most severe and useful studies, by a strict observation of the rules of honour and virtue, by frequent and serious reflections on the mistaken measures of the world, and the true end and happiness of mankind, he should in all respects qualify himself bravely to run the race that is set before him, to deserve the character of great and good in this life, and be ever happy hereafter-this were amazing and almost incredible. Yet all this, and more than this, SIR, might I justly say of you, did either your modesty permit, or your character stand in need of it. I know it might deservedly be thought a vanity in me to imagine that anything coming from so obscure a hand as mine could add a l.u.s.tre to your reputation. But, I am withal sensible how far I advance the interest of my own, by laying hold on this opportunity to make it known that I am admitted into some degree of intimacy with a person of your exquisite judgment. And, with that view, I have ventured to make you an address of this nature, which the goodness I have ever experienced in you inclines me to hope will meet with a favourable reception at your hands. Though I must own I have your pardon to ask, for touching on what may possibly be offensive to a virtue you are possessed of in a very distinguishing degree. Excuse me, SIR, if it was out of my power to mention the name of SIR JOHN PERCIVALE without paying some tribute to that extraordinary and surprising merit whereof I have so clear and affecting an idea, and which, I am sure, cannot be exposed in too full a light for the imitation of others,

Of late I have been agreeably employed in considering the most n.o.ble, pleasant, and comprehensive of all the senses(284). The fruit of that (labour shall I call it or) diversion is what I now present you with, in hopes it may give some entertainment to one who, in the midst of business and vulgar enjoyments, preserves a relish for the more refined pleasures of thought and reflexion. My thoughts concerning Vision have led me into some notions so far out of the common road(285) that it had been improper to address them to one of a narrow and contracted genius. But, you, SIR, being master of a large and free understanding, raised above the power of those prejudices that enslave the far greater part of mankind, may deservedly be thought a proper patron for an attempt of this kind. Add to this, that you are no less disposed to forgive than qualified to discern whatever faults may occur in it. Nor do I think you defective in any one point necessary to form an exact judgment on the most abstract and difficult things, so much as in a just confidence of your own abilities.