The Molyneux Problem - Jraissatijraissati.com/PHIL201/Davis_1960_TheMolyneuxProblem.pdf · THE MOLYNEUX PROBLEM . 393 . to reduce the Lockean dualism of sensation and reflection to

The Molyneux ProblemAuthor(s): John W. DavisReviewed work(s):Source: Journal of the History of Ideas, Vol. 21, No. 3 (Jul. - Sep., 1960), pp. 392-408Published by: University of Pennsylvania PressStable URL: http://www.jstor.org/stable/2708144 .

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THE MOLYNEUX PROBLEM

BY JOHN W. DAViS

"Preparer et interroger un aveugle ne, n'efut point et6 une occupation in- digne des talens reunis de Newton, Descartes, Locke et Leibnitz."-Diderot

I. INTRODUCTION

The general conditions of the Molyneux problem are as follows: assume a man born blind, who while blind has learned to distinguish a globe from a cube. Would he, upon having his sight restored, be able to distinguish the globe from the cube by sight before he had touched them? Because of its theoretical significance the problem was discussed by some of the most eminent thinkers of the XVIIIth century including Locke, Berkeley, Leibniz, Voltaire, Diderot, and Condillac. Like many great problems, it has not been solved, appear- ing full-blown as a subject of occasional comment throughout the XIXth century, although by then the terms of reference of the issues at stake became that of the nativism-empiricism controversy in psychology. The attitudes toward the problem are worth tracing in some detail because of the light thrown on some important issues of XVIIIth-century theories of knowledge, and because of the instruc- tiveness of its results in the history of psychology.' The present article does not pretend to be a full chronicle of the problem. I have tried, however, to take account of all significant discussions.

The problem is primarily an epistemological one, involving the nature of the transition from sensation to judgment. A definitive answer to the problem would presumably provide an answer to some of the most vexing questions of empiricism, sensationalism and rationalism, as we have come to name these issues. Empiricism is the doctrine that all our ideas-the materials of knowledge-come from experience. As Locke, who may serve as our principal exponent of the empirical doctrine, expounded it, experience has two sides: sensation and reflection. On this view, all knowledge arises in connection with sense experience, but the mind, through its simple ideas of reflection, is able to work on the data thus furnished by the senses and at the same time is able to be aware of its own operations. Sensationalism, a variant of empiricism with Condillac as its prototype, is an attempt

1 The Molyneux problem is also one of the main sources of the conceit of the blind man so popular in XVIIIth-century literature, although this paper does not treat this phase of the problem. See Marjorie Hope Nicolson, Newton Demands the Muse (Princeton, 1946) 83-85, and Kenneth MacLean, John Locke and English Literature of the Eighteenth Century (New Haven, 1936), 106-108 and passim. It should be noted that Miss Nicolson errs in stating that Molyneux discussed this problem more fully in the Dioptrica Nova. There is no mention of the problem either in the edition of 1692 or in the reprint of 1709.

392



THE MOLYNEUX PROBLEM 393

to reduce the Lockean dualism of sensation and reflection to a monism in which sensation is primary and reflection is only transformed sensation. For the sensationalist, all knowledge is given in sensation. Rationalism, as held for example by Leibniz, would grant that data are obtained from both sensation and reflection, but would also insist that certain knowledge can be obtained only by means of self-evident principles of which sensation and reflection give us only a confused and provisional view.

Stated in this way, it can be seen readily that those who answered the Molyneux problem negatively would tend to be classified as either empiricists or sensationalists and that those who gave an affirmative answer would tend toward rationalism. One must, of course, beware of reading more precision into this classification than it will bear, since the terms 'rationalism' and 'empiricism' are best understood as names for general tendencies in thought and not as descriptive of mutually exclusive alternatives.

II. MOLYNEUX, LOCKE, AND BERKELEY: THE NEGATIVE ANSWER

William Molyneux, author of the Dioptrica Nova (1692), an influ- ential early XVIIIth-century treatise in optics, was a man very much aware of the problems of the blind because of his wife's loss of sight. He proposed what he referred to as a 'jocose problem' in a letter to Locke on March 2, 1692: Suppose a man born blind, and now adult, and taught by his touch to distinguish between a cube and a sphere (suppose) of ivory, nighly of the same bigness, so as to tell when he felt one and t'other, which is the cube, which the sphere. Suppose then, the cube and sphere placed on a table, and the blind man to be made to see; query whether by his sight, before he touch'd tllem, he could now distinguish and tell which is the globe, which the cube. I answer not; for tho' he has obtained the experience of how a globe, how a cube affects his touch, yet he has not yet attained the experience, that what affects my touch so or so, must affect sight so or so; or that a protuberant angle in the cube that press'd his hand unequally, shall appear to his eye as it does in the cube.2

In the latter part of March of the same year Locke replied to this letter, saying that " your ingenious problem will deserve to be published to the world." 3 Thereupon Locke inserted the problem in the second edition (1693) and all remaining editions of the Essay Con- cerning Human Understanding, presenting Molyneux's problem as just given without substantial difference. Molyneux refers to his problem briefly once more in print.4

2 Some Familiar Letters between Mr. Locke and several of his Friends (London, 1708), 37-38. 3Ibid., 43.

4 In December of 1695, after his correspondence with Locke had ripened into warm friendship, Molyneux enclosed a letter from Edward Synge to a Dr. Quayl, in



394 JOHN W. DAVIS

It is generally assumed that Locke's position and that of Molyneux in regard to the query are identical, since both reply to it in the negative. Both Jurin 5 and Priestley 6 conclude quite correctly that although Molyneux and Locke agreed on the answer their grounds seem different. Locke, in commenting upon Molyneux's query, says: I agree with this thinking gentleman ... and am of opinion that the blind man, at first sight, would not be able with certainty to say which was the globe, which the cube, whilst he only saw them; though he could unerringly name them by his touch, and certainly distinguish them by the difference of their figures felt.7

As Jurin points out, in Molyneux's original statement of the problem, the blind man is debarred only from touching the globe and the cube, whereas Locke imposes the additional condition that the blind man make the identification at first sight, i.e., presumably wlthout walking around and viewing the objects from various sides. The possible dif- ferences in the solution thus generated are better considered after Leibniz's affirmative solution to the Molyneux problem has been can- vassed.

Berkeley commented on the problem negatively both in its original version and in versions he constructed to exploit for various philosophical purposes.8 For Locke the Molyneux problem served to illustrate the " mental interpretation of the data of sense "; 9 for Berkeley it plays a much wider role. Cassirer goes so far as to say that " The New Theory of Vision, which forms the prelude to Berkeley's philosophy, and contains all his ideas implicitly, is nothing but an attempt at a complete systematic development and elucidation of Molyneux's problem." 10 In Berkeley's early notebooks, the Philosophical Com- mentaries (written from 1707-1708), there are thirteen specific references to the problem; Berkeley uses it for a variety of purposes, the

which Synge answered the question in the affirmative. After noting that he has enclosed a copy of Synge's letter, Molyneux adds that he is not budged by Synge's contentions.

r James Jurin (1684-1750) edited Vols. XXXI-IV of the Philosophical Trans- actions. In an age of great polemicists, he was one of its best-known. He was an ardent Newtonian and a defender of the theory of fluxions, which involved him in a famous controversy with Berkeley.

6 Joseph Priestley (1773-1809), Vision, Light, and Colours (London, 1772), 720. 7John Locke, Essay Concerning Human Understanding, ed. A. C. Fraser (Oxford,

1894), I, 187. 8 Berkeley's remarks on the Molyneux problem in his published writings should

be studied in conjunction with Luce's references and comments on entries 27 and 28 of the Philosophical Commentaries, ed. A. A. Luce (London, 1944). Cf. Colin Tur- bayne, "Berkeley and Molyneux on Retinal Images," this Journal, XVI (1955), 339-355. 9 Ibid., editor's note to entry 27, 326.

10 Ernst Cassirer, Philosophy of the Enlightenment (Princeton, 1950), 109.




main one being to illustrate the heterogeneity of sight and touch. We can best summarize his comments by considering only those works which Berkeley meant for publication, and limiting ourselves to considering his works on the psychology and philosophy of vision, for it is here that Berkeley gives his fullest and most interesting remarks on the problem; elsewhere he either refers to these works on vision or recapitulates his argument without adding new material.

Berkeley's Essay towards a New Theory of Vision (1709) has a precise purpose indicated in its opening section: My design is to shew the manner wherein we perceive by sight the distance, magnitude, and situation of objects. Also to consider the difference there is betwixt the ideas of sight and touch, and whether there be any idea common to both senses.1"

Consider first the latter thesis. As Karl Aschenbrenner strikingly puts it, Berkeley " construes the outcome of the famous 'experiment ' with Molyneux's blindman in such a way that it must always be false to say ' I see what I touch.' 1' 12 This heterogeneity of sight and touch is Berkeley's most original contribution to the psychology of vision. He states the thesis as follows: The extension, figures, and motions perceived by sight are specifically dis- tinct from the ideas of touch called the same names, nor is there any such thing as one idea or kind of idea common to both senses.13 The demonstration of this thesis consists of three arguments. In the first, Berkeley employs one of his own versions of the Molyneux problem, alleging that " a man born blind would not at first reception think the things he saw were of the same nature with the objects of touch, or had anything in common with them." 14 The second argument urges that because visual appearances are qualitatively different from tactual appearances, there can be nothing common to both senses; this is similar to his third argument that the visible and tangible are not 'homogeneous' and thus cannot be added. In section

llGeorge Berkeley, Essay towards a New Theory of Vision, section 1 in The Works of George Berkeley, ed. A. A. Luce and T. E. Jessop (London, 1948), I, 222-3. All quotations from Berkeley, save quotations from the previously cited edition of the Philosophical Commentaries, will be from this edition.

12 George Berkeley; Lectures delivered before the Philosophical Union of the University of California in honor of the two hundredth anniversary of the death of George Berkeley (Berkeley, 1957), 44.

13 Berkeley, Essay, section 127, ed. cit., 222-223. Boring suggests that Berkeley's doctrine of heterogeneity helps to fix upon psychology one of its most important principles of classification, the doctrine of sensory attributes. It develops out of Aristotle's classification of the senses and Locke's characteristic stress on the sensory nature of ideas. See E. G. Boring, History of Experimental Psychology (2nd ed.; New York, 1950), 182-183. 14 Berkeley, Essay, section 128, 223.



396 JOHN W. DAVIS

132, Berkeley offers Locke's and Molyneux's solution to the Molyneux problem as " a further confirmation of our tenet." 15 It is not, however, until section 135 that Berkeley's own attitude toward the Moly- neux problem comes to the fore. His aniswer is in the negative, but his denial is far more sweeping than that of either of his predecessors. For Berkeley, the blindman would not even understand the question; it would seem to him " downright bantering and unintelligible." 16

Berkeley wished also to show how distance, magnitude, and situation (orientation) are perceived by sight. In each case, the Molyneux problem is used to support his contentions. In the case of distance, Berkeley argues that we do not immediately see distance; an object itself is seen immediately as part of the data of consciousness, but how far the objects are from us is not immediately known by sight. His well-known solution is, of course, that perception of distance is " an act of judgment grounded on experience." 17 His classic account men- tions most of the primary and secondary criteria that are recognized today.'8 Berkeley uses his own version of the Molyneux problem in this discussion of distance: ... it is a manifest consequence that a man born blind, being made to see, would at first have no idea of distance by sight; the sun and stars, the re- motest objects as well as the nearer, would all seem to be in his eye, or rather in his mind.19

Berkeley's discussion of magnitude and situation follow similar lines, and in sections 79 and 106 there are corresponding passages in which the Molyneux problem is a test case in Berkeley's demonstration.

III. THE AFFIRMATIVE ANSWER

Leibniz, after a full discussion of the problem in the New Essays,20 responds to the query with a carefully qualified affirmative. In his answer he explicitly imposes a condition implicit in the original problem; the man with restored sight must know that objects before him to be distinguished are respectively a globe and a cube. The judgment is made, according to Leibniz, " by the principles of reason,

15 Ibid., section 132, 225. In the following section, 133, Berkeley further maintains that the solutions of Locke and Molyneux require to be valid a heterogeneity between sight and touch which Locke had denied. For Locke, there are " simple ideas of divers senses " such as those of space and extension which " we can receive into our minds ... both by seeing and feeling."' Locke, Essay, II, Ch. 5, 158.

16 Berkeley, Essay, section 135, 226. 17 Ibid., 171. 18 For an analysis of Berkeley's contribution to the psychology of space-percep-

tion, see Boring, History, 179-186. 19 Berkeley, Essay, section 41, 186. 20Gottfried Leibniz, New Essays Concerning Human Understanding, tr. A. G.

Langley (New York, 1896), II, ix, 8.




united with that sense knowledge which touch has before furnished him." 21 The data furnished by sense upon which reason could oper- ate to make the correct judgment are that . . . in the globe there are no points distinguished by the side of the globe itself, all there being level and without angles, while in the cube there are eight points distinguished from all the others.22

Proof of this thesis, Leibniz contends, comes from the fact that the blind have " rudiments of a certain natural geometry." 23 Suppose, further, a blind man and a paralytic learn geometry. Their two ge- ometries " must meet and agree, and indeed return to the same ideas, although there are no common images." 24 Here Leibniz admits the heterogeneity insisted upon by Berkeley, but claims it to be a heterogeneity of images, not a heterogeneity of exact ideas " which consist in definitions." 25 By this distinction Leibniz saves himself from the confusion over imaginability and conceivability so common in Locke and Berkeley.

Furthermore, Leibniz specifically excludes from his answer the condition that the judgment be made at 'first sight' which Locke had imposed. Leibniz grants that the blindman at first would be " dazzled and confused by the novelty." 26 Such a qualification does in fact modify Leibniz's affirmative answer.

Jurin, whose distinction between the views of Locke and Molyneux has already been commented upon, accepted the Berkeleian doctrine of the heterogeneity of sight and touch.2 He agreed with Berkeley that it is only suggestion and experience that connects the two. For Jurin, however, the Molyneux problem does not tend to support the Berkeleian theory. His statement of the problem amplifies the account of Leibniz somewhat. For Jurin, there would be a similarity in our sense-data (called 'ideas' in the terminology of the period) of the globe no matter from what perspective it were touched or viewed. Such a similarity would be lacking in the case of the cube with its eight points. Thus the individual might reason out which were which, particularly if he knew that an absolute distinction existed between them. This same point was also made by Edward Synge.28

21 Ibid., 139. 22Ibid. 23 This suggestion foreshadows the famous case of Saunderson, the blind mathe-

matician of Cambridge, discussed more fully later by Diderot. The notion of 'natural geometry' is as old as Kepler and is made famous by Descartes.

24Leibniz, New Essays, 139. 25Ibid. 28Ibid. 27 James Jurin, " Remarks " in Robert Smith, A Compleat System of Opticks (4

bks.; Cambridge, 1738), II, 27-29. 28 Edward Synge (1649-1741) was the author of the Gentleman's Religion. For

an account of Synge's writings, see John Nichols, Literary Anecdotes (9 vols.; Lon- don, 1812-1816), I, 378.



398 JOHN W. DAVIS

Let us pause to draw the threads together. The positions of Locke and Leibniz differ by but a hair's breadth. This is because Locke's empiricism is broadly conceived. Despite some commentators to the contrary, Locke's philosophy of mind, and more particullarly his doctrine of our knowledge of the external world, is not a view of the mind as a purely passive instrument, but rather of a mind pregnant with the capacity to function with data which sense supplies. Leibniz in- vokes specifically his own ' principles of reason' which are perhaps tacitly assumed in Locke. Berkeley, on the other hand, although not appropriately called a sensationalist since he does not attempt to reduce all perception and judgment to transformed sensation, has a nar- rowly conceived empiricism as far as our knowledge of the external world is concerned. Berkeley allows two classes of ideas, ideas of sense and ideas of imagination.29 The ideas of sense by which we know the external world " are not excited at ra-ndom . . . but in a reg- ular train or series, the admirable connexion whereof sufficiently testifies the wisdom and benevolence of its Author." " Although Leibniz grants Berkeley's thesis of the heterogeneity of sight and touch as far as images (or what we would call sense-data) are concerned, his 'exact definitions' have no analogue for Berkeley in connection with the Molyneux problem. Berkeley's denial is in fact more sweeping than either Locke's denial or Leibniz's qualified affirmation.

IV. THE EXPERIMENTAL TEST

In 1728 there appeared in the Philosophical Transactions an account by William R. Chesselden, a famous anatomist and surgeon, of the successful operation for cataract on a thirteen- or fourteen-year- old boy who had lost his sight very early in life. This was the first of a number of such cases,31 and though it is the most famous, it is by

29Cf. Berkeley, Principles of Human Knowledge, section 1 in Works, II, 41, with editor's footnote thereto.

30 Berkeley, Principles, section 30, 53. Knowledge of mind for Berkeley is not, of course, ideational but notional. Whether or not this notional knowledge is to be called empirical is a debatable problem. On Berkeley's doctrine of notional knowledge, see the present author's article, " Berkeley's Doctnrne of the Notion," Review of Metaphysics (March 1959), 378-389.

31 The Chesselden case is reproduced in full in Fraser's edition of Berkeley's works. George Berkeley, Berkeley's Complete Works, ed. A. C. Fraser (4 vols.; Oxford, 1901), II, 411-413. Fairly complete accounts of the classical cases with commentaries are to be found in William Preyer, The Development of the Intellect (New York, 1889), appendix C and in B. Bourdon, La Perception visuelle de l'espace (Paris, 1902), 359-391. A bibliography of cases is to be found in W. IUhthoff's contribution to T. Engelman's et al., Beitrage zur Psychologie und Physio- logie der Sinnesorganes; Hermann von Helmholtz als Festgruss zu seimem siebzig- sten Geburtstag (Hamburg and Leipzig, 1891). To these cases should be added that commented on by Robert Latta in the British Joural of Psychology, (1904),




no means the best reported in the literature. The boy in this case failed to recognize by sight his cat which he had known prior to the operation by touch. Upon seizing her, he said, " So, puss, I shall know you another time." One fact, however, comes forth clearly in this case, although its significance for the Molyneux problem does not seem to have been appreciated fully because of the atomistic psychology of the time. We know now that space-perception is slowly acquired; it is, as it were, 'built up' over a considerable period of time. The terms of the problem, in requiring the subject to answer immediately upon restoration of sight, ask for an answer to what is not, and can never in the nature of the case be, an experimentum crucis. But Berkeley and a host of others took the Chesselden case as a confirmation of their own views. After summarizing the Chesselden case in an incomplete and somewhat inexact way, Berkeley wrote: " Thus, by fact and experiment, those points of the theory which seem the most remote from common apprehension were not a little confirmed, many years after I had been led into the discovery of them by reasoning." 32

From an extensive literature, an extract from one of the best reported and most interesting cases is perhaps worth quotation; it indicates the general style of all the cases. The investigator in this case was Franz and the date was 1841:

The windows of the room were darkened with the exception of one, toward which the patient, closing his eye, turned his back. At the distance of three feet, and on a level with the eye, a solid cube and a sphere, each of four inches in diameter were placed before him. I now let him open his eye. After attentively examining these bodies, he said he saw a quadrangular and a circular figure, and after some consideration he pronounced the one a square and the other a disk. His eye being closed, the cube was taken away, and a disk of equal size substituted and placed next to the sphere. On again opening his eye he observed no difference in these objects, but regarded them both as disks. The solid cube was now placed in a somewhat oblique position before the eye, and close beside it a figure cut out of pasteboard, representing a plane outline prospect of the cube when in this position. Both objects he took to be something like flat quadrates. ... On the conclusion of these experiments I asked him to describe the sensations the objects had produced, whereupon he said that immediately upon opening his eye he had discovered a difference in the two objects, the cube and the sphere, placed before him, and perceived that thev were not drawings; but that he had not been able to form from them the idea of a square and a disk, until he perceived a sensation of what he saw in the points of his fingers, as if he really touched the objects. When I gave the three bodies, the sphere, cube, and

I, 135-150. Test-cases are largely confined to the XIXth century, for, as Parsons points out, " such cases now rarely escape operation in infancy." Sir John H. Par- sons, An Introduction to the Theory of Perception (Cambridge, 1927), 157-158.

32Berkeley, Theory of Vision Vindicated, section 71, 276.



400 JOHN W. DAVIS

pyramid, into his hand, he was much surprised that he had not recognized them as such by sight, as he was well acquainted with them by touch.83

V. THE MOLYNEUX PROBLEM IN FRANCE

The Molyneux problem reached France with Voltaire's populariza- tion of the new philosophy of Newton, Locke, and Berkeley. Vol- taire's Elements of Newton's Philosophy (1738) treats the Molyneux problem in a passage following a terse summary of the Berkeleian theory of vision. Voltaire, after having expounded Berkeley's views of perception of distance, magnitude, and situation, writes:

All this could only be explained, and made incontestable by some Person born blind, and restored to the sense of Sight. For if this blind Person, at the Moment he received Sight, had judged of Distances, Magnitudes, and Situations, it had been true that the optick Angles formed that instant in his Retina, had been the immediate Causes of his Thoughts. Dr. Barclay [Berkeley] accordingly has assured us after Mr Locke (and indeed has gone beyond Mr Locke on this Point) that neither Situation, Magnitude, Dis- tance, nor Figure, would be at all discerned by a Blind Person, at the In- stant his Eyes should receive Light.34

After thus accepting Berkeley's opinions, Voltaire further maintains that the Chesselden case " confirmed all that Locke and Berkeley had foreseen." 35 His brief summary, however, has a lucidity and clarity in what it suggests that is quite lacking in the record as published by Chesselden, although it might be remarked that the clarity results because the subtleties of the problem have been missed.

Condillac, who was familiar with Berkeley and the Chesselden case by way of Voltaire's Elements, considered the Molyneux problem at some length in his first work, the Essais sur l'origine des connoissances humaines (1746). At this stage of his work, Condillac was a faithful Lockean empiricist, admitting two sources of knowledge in sensation and reflection. The individual will be able to reflect on that which sensation had occasioned in him and will be able " se former des idees de differentes operations de son ame." 36 In 1746, Condillac is unwilling to accept Locke's analysis of perception or Berkeley's theory of vision because each involves unconscious judgments which for Con- dillac are unempirical.37 This stress on a rigorous empiricism, which will later become sensationalism, is characteristic of Condillac. The

93 J. C. A. Franz, communicated to Philosophical Transactions by Sir Benj. C. Brodie (London, 1841), I, 59-69, quoted from Preyer, Development of Intellect, 310-311.

34 F. M. A. Voltaire, Elements of Sir Isaac Newton's Philosophy, trans. J. Hanna (London, 1738), 59-71. 35 Ibid.

36 Etienne Condillac, Essais sur l'origine des connoissances humaines in Oeuvres de Condillac, ed. G. LeRoy (Paris, 1947), I, part I, section 4, 6.

37 Ibid., section 6, 54-56 deal with Condillac's criticisms of Locke and Berkeley.




most interesting feature of Condillac's early treatment of the Moly- neux problem is that he accuses of bias those who find in the Ches- selden case co firmation of their speculations. He writes: C Ceux qui observolent cet aveugle-n6 au moment qu'on lui abaissoit les cata- ractes, esperoient de voir confirmer au sentiment pour lequel ils etoient prevenus."} 38

In his Treatise on the Sensations (1754), a work in which the Molyneux problem is the linch-pin of the whole, Condillac offers several interesting crticisms of Locke. In the first place, Condillac points out that the Locke-Molyneux condition that the cube and globe be of approximately the same size is superfluous. Secondly, as- suming that they must be of the same size seems to entail that sight without the aid of touch can give different ideas of size. This contention, however, contradicts the Locke-Molyneux assumption that shape cannot be diseriminated by sight alone. Thirdly, Condillac criticizes Locke as inconsistent in maintaining that an eye which could discern position, size, and distance could not discern shape. For Condillac, the eye alone could judge none of these; the upshot for him in 1754 is a thoroughgong adherence to the Berkeleian theory of vision. For him, "Berkeley was the first to think that sight alone could not judge of these things (i.e., position, size, distance and shape)." 3 Lastly, Locke is chastised for not recognizing that " judgments have some part in all our sensations."y 0 This point is of some interest because it shows the general manner in which Condillac reduces Locke's dualism of sensa-tion and reflection to a sensationalism in which reflection is only transformed sensation. After a fairly full summary of the Chesselden case, Condillac in Chapter 6 of Part III details the precau- tions necessary if one is properly to interrogate the blind. In this chapter, Condillac shows more sophistication about the difficulties involved in such test-cases than anyone had hitherto displayed.

Diderot's Letter on the Blind for the use of those who would see (1749), referred to by authorities as the first scientific study of the blind,4' studies the Molyneux problem as an issue between Locke and Condillac. His tendency to side with Locke was the main factor in the modification of Condillac's view from the Essais to the Treatise.42

38 Ibid., 59 39 Etienne CondiHac, Treatie on the Sensations, tr. Geraldine Carr (Los Angeles,

1930), Part II, Chapter 4, section 3, 171. 40Ibid. 41 Cf. Pierre Vley, who was himself a blind professor at Caen University, "A

propos de la Lettre sur les Aveugles," Revue du Dix-It?eme Scte, I, (1913), 412, 421-422, and the remarks of Gabriel Farrell, one-time director of the Perkins Insti- tution for the Blind, quoted in A. M. Wilson, Diderot: The Testing Year, 1713- 1759 (New York, 1957), 99.

42 Cf. Denis Diderot, Lettre sur les Aveugles, ed. Robert Niklaus (Geneva, 1951), editor's introduction, xlvi.



402 JOHN W. DAVIS

His real contribution to the Molyneux problem is, however, in his suggestion that the blind live in a different world from the sighted and that questioning them is a matter of infinite patience and care before an answer can be obtained which is in any sense conclusive. Although one does not have to follow Diderot in his suggestion that because the ideas of the blind are different from the sighted so must their morality and religion be different, it was undoubtedly speculation upon such a question that led Diderot to consider that perhaps the crucial case might be that of a highly intelligent and gifted blind person. He found such an elite subject in Nicholas Saunderson,43 who is the mouthpiece for Diderot's scepticism in the Letter. Diderot's own answer to the Molyneux problem is that the first time the eyes of one born blind open to the light, he will see nothing at all; some time will be necessary for his eye to pra;ctise sight; it will prac- tise alone and without the aid of touch, and will eventually distinguish not only colours but the main outlines of objects.44

Contrary to most French philosophy of the XVIIlth century, which was empiricist or sensationalist,45 it is clear that Diderot in this passage, representing his considered opinion on the Molyneux problem, has chosen the rationalist option, since there is no mutual education of the senses enabling us to learn spatial form and it is not only the eye which experiments, but the brain.48

43 icholas Saunderson (1682-1739), Lucasian Professor of Mathematics at Cambridge, lost his sight at one year of age. Appended to Saunderson's Elements of Algebra (Cambridge, 1740), I, l-xix, is "an account of the author's life and character." The facts relative to the life of Saunderson and examples of his abilities were available to Diderot from this source. His account of the death of Saunderson in the Letter on the Blind, however, is fictional.

44Denis Diderot, " The Letter on the Blind," Diderot's Early Philosophical Works, tr. Margaret Jourdain (Chicago, 1916), 131.

45 There are three other comments on the Molyneux problem in the sensationalist French philosophy of the XVIIIth century which deserve mention. LaMettrie (1709-1751), one of the more extreme sensationalist philosophers of the period, con- cluded that the Chesselden case, which he knew through Voltaire's Elements, confirmed Locke's position on the problem. The title of Ch. XV of his Traite de I'Ame, "Histoires qui confirment que toutes les idees viennent des sens," gives an accurate indication of his viewpoint. Julien LaMettrie, Oeuvres Philosophiques (London, 1751), 186. A fuller and more accurate account of the Chesselden case than Vol- taire had provided is given by Georges Buffon, " Histoire naturelle de l'homme," Oeuvres Completes (Paris, 1846), Tome 4, Part 2, 138-139. Condorcet asserted that the Chesselden case confirmed Locke's contention; " il faut que l'homme ap- prenne a voir comme 'a marcher." M. J. A. Condorcet, Oeuvres, ed. O'Connor & Arago (Paris, 1847), II, 121.

46 This point became clear to me only after I had read the excellent introduction to the Letter in Oeuvres Philosophiques de Diderot, ed. Paul Verniere (Paris, n.d.), esp. 76-77.




V. LATER HISTORY OF THE MOLYNEUX PROBLEM IN GREAT BRITAIN

The Molyneux query in Great Britain is closely tied to the history of the influence of Berkeley's New Theory of Vision and its com- panion piece, the Theory of Vision Vindicated (1733).47 The first traceable mention of the Molyneux problem in Scotland was in Wil- liam Porterfield's A Treatise on the Eye (1759), one of the standard works on vision in the first half of the century. Porterfield, who denied the Berkeleian theory that judgments of distance and orientation were made by " custom and experience," and instead asserted that such judgments occurred by " an original, connate and immut- able Law, to which our minds have been subjected from the Time they were first united to our Bodies "1 48 gave his affirmative solution to the Molyneux query in the following words: ... the Idea which a Blind man must needs form of a Globe by his Touch, will be this, that it is a body which is exactly alike on all sides; for let him roll it as often as he will between his Hands, he can find no manner of Dif- ference between the one Side and the other: But this is the very Idea which at first Sight such a Man will form of it by his Eyes, and consequently he must at first sight know it to be a Globe, and not a Cube.49

We have met this position before, but Porterfield expresses it with clarity.

Reid in his Inquiry into the Human Mind (1764) takes the empiricist stand that the blind man could not " discern that this was a cube, that a sphere." 50 Sir William Hamilton, who can write of Berkeley's theory of vision " that nothing in the compass of inductive reasoning appears more satisfactory," although demurring its value in the case of lower animals,5' nevertheless, in commenting on the passage from Reid quoted above, answers the Molyneux query in the affirmative. His position, similar to that of Jurin and Leibniz, is that:

A sphere and a cube would certainly make different impressions on him; but it is probable that he could not assign to each its name, though, in this par-

47 An important early full-scale report of a blind and deaf boy, James Mitchell, was made by Dugald Stewart, first published in Transactions of the Royal Society of Edinburgh (1815), Vol. VII, Part 1 and included in The Collected Works of Dugald Stewart, ed. Sir Wm. Hamilton (Edinburgh, 1854), IV, 300-370. Stewart does not deal with the Molyneux problem directly, but asserts that the " result appears, on the whole, as favourable as could reasonably have been expected, to the Berkeleian theory of vision." Stewart, Works, IV, 309.

48 Wm. Porterfield, Treatise on the Eye. The Manner and Phaenomena of Vi- sion (2 vols.; Edinburgh, 1759), II, 414.

49 Ibid., 415. 0 Thomas Reid, Works, ed. Wm. Hamilton (6th ed.; Edinburgh, 1863), I, 136.

5' Hamilton in Reid, Works, I, 182.



404 JOHN W. DAVIS

ticular case, there is good ground for holding that the slightest consideration would enable a person, previously acquainted with these figures, and aware that the one was a cube and the other a sphere, to connect them with his anterior experience, and to discriminate them by name.52 The only way that these two quoted statements can be rendered con- sistent is to assume that all Reid means by the Berkelelan theory is the contention that sight and touch have no connection except that formed by experience, rather than the more sweeping Berkeleian as- sertion that the question would be unintelligible to the blindman whose sight was restored.

Adam Smith, a faithful Berkeleian in the theory of vision, grants that although there be " no resemblance between visible and tangible objects," there " seems to be some affinity or correspondence between them sufficient to make each visible object fitter to represent a certain precise tangible object than any other tangible object." 5 This affinity or correspondence, however, between the visible and the tangible "could not alone, and without the assistance of observation and experience, teach us, by an effort of reason, to infer what was the precise tangible object which each visible one represented." 54

The first thoroughgoing examination of Berkeley's theory of vision that reaches a negative verdict concerning its main points was that of Samuel Bailey in 1842.55 Among his other anti-Berkeley arguments, Bailey denies that the Chesselden case supports the Berkeleian doctrine of the heterogeneity of the two senses. He further believes that the Home case of cataract operation on John Salter,56 in which the boy asserted correctly after some thought ten minutes after the operation that a piece of paper was round, "in fact, solved the problem proposed by Mr. Molyneux to Mr. Locke." 57 Balley then goes on to give the standard affirmative answer to the query:

52Ibid., 137. 53 Adam Smith, Essays on Philosophical Subjects (London, 1795), 227. 64 Ibid., 229. 55 Samuel Bailey, A Review of Berkeley's Theory of Vision designed to show the

unsoundness of that celebrated speculation (London, 1842). Although Mill does not treat the Molyneux problem directly, his review of Bailey should be noted at this point. See John Stuart Mill, Dissertations and Discussions (London, 1859), II, 84- 119.

56Everard Home, Philosophical Transactions of the Royal Society (London, 1807), I, 83-87. An adequate extract of Home's two cases is to be found in Preyer, Development of the Intellect, 296-300.

57Bailey, Review of Berkeley, 218. One can hardly consider the Home case of John Salter as conclusive as Bailey does, since the boy had sufficient sight despite the cataracts to distinguish colors "' with tolerable accuracy.' Home in Preyer, Development of Intellect, 297. It is thus difficult to know how much vision the child had before the operation.




It is surprising that these two philosophers should have answered the question so absolutely in the negative. If we admit, as Locke does ... that the eye naturally distinguishes plane figures, it follows that it can consequently perceive angles and curves in all their variety. The touch can do the same. There are, then, relations existing between lines, which both these senses are capable of perceiving. The identity of form, therefore, between a visible right angle, and a tangible right might be recognized, although these two objects had never been simultaneously received.58 Bailey then quotes Diderot favorably and asserts that the quickness of recognition of form " in the case of a blind person suddenly en- dowed with sight, would doubtless vary with circumstances." '9

T. K. Abbot in Sight and Touch (1864) offers an instructive suggestion concerning the Molyneux problem in the course of his detailed and destructive criticism of Berkeley: Let the reader reflect how much handling and consideration of an unfamiliar form would be necessary, if the eyes were shut, before we could obtain anything like an accurate idea of its visible appearance.60 After suggesting that an affirmative answer is possible to the query because of the difference in the deliverances to sight of the cube from the globe, Abbot goes on to suggest: ... if the blind are capable of acquiring the ideas in question, they will, on being made to see, be competent to name correctly the globe and cube which they have previously felt. Consequently, if upon being fairly examined they appear incapable of doing so, it will follow that the defect is not in sight but in touch; not in their new sense, but in their old ideas.6'

Monck in Space and Vision (1872) suggests that in attempts to verify the Molyneux query experimentally circles and squares be substituted for spheres and cubes since the visual appearances of the former would vary less from different perspectives. Secondly, he suggests that neutral terms like 'alpha' and 'beta' be substituted for ' circle ' and 'square' since it is "too often forgotten that different men may employ the same terms with the same denotation, but with totally different connotations," and this "may be the case with the space-perception of the blind man and the seeing man." 62 Lastly, a triangle and a square should be used rather than a circle and a square to eliminate the fact that "the uniformity of the circular outline would give considerable scope for guessing if the patient was at all quick." 68

58 Bailey, Review of Berkeley, 220. " Ibid. I Thomas K. Abbot, Sight and Touch: An Attempt to disprove the received (or

Berkeleian) Theory of Vision (London, 1864), 141. 61 Ibid., 142. 62 W. H. S. Monck, Space and Vision: An Attempt to deduce all our knowledge

of space from the sense of sight (Dublin, 1872), 80. 6 Ibid., 81.



406 JOHN W. DAVIS

VI. THE QUERY AND THE NATIVISM-EMPIRICISM CONTROVERSY

The Molyneux problem of the XVIlIth century is the progenitor of the nativism-empiricism controversy of the latter half of the XlXth century. The nativism-empiricism controversy was concerned over whether knowledge of space was innate or learned. The proxi- mate source of the debate was Kant's doctrine of the a priori character of spatial intuition.04 The debate over nativism and empiricism was inconclusive, as most such debates are, since most sophisticated nativists came to recognize that the perceiver's spatial organization was modified and developed in experience, and empiricists recognized that something congenital was brought by the perceiver in his organization of space.

So far as any precision can be brought to the issues, they may be stated a la Berkeley. Berkeley had contended that the immediate objects of vision are light and colors, that visual data are arbitrary signs which suggest to the mind ' outness ' by repetition in the same fashion in which words come to suggest things by repetition, and that tactual data are indispensable as an auxiliary aid to visual data-a position maintained by all empirical theories.65 As in the Molyneux problem, the empiricists gave to experience as much function as possible in spatial organization, whereas the nativists tended to minimize the role of experience and maximize the role of unmodified congenital intuition. Ribot has pointed out that the debate may be summed up in Berkeleian terms. He writes: What is the peculiar object of sight? This very simple question sums up the debate. If we reply: color, we are empiricists. If we reply: colored extension, we cast our lot with the nativists.06

Let us consider the arguments of empiricism against nativism and vice versa to see whether the substantive issues will throw some light upon the Molyneux problem. The main arguments offered by the empiricists against the nati+vists were, first, the logical argument that nativism introduced an unnecessary hypothesis, an innate intuition of space. Secondly, the empiricists contended that facts were burked in the nativrist analysis since nativists are compelled to grant that " in the great majority of cases, these (original) sensations must be sup- plemented by very profound experiential knowledge." 67

Against empiricism, nativism contended, first with a factual argument, that evidence from the fact that animals could see depth upon

64Although Kant's name gave prestige to many nativists, actually the controversy was over the psychological genesis of the idea of space, a purely phenomenal question, and not a problem of a transcendent order concering the ultimate origin of the notion of space. On this point, see Theodore Ribot, German Psychology To- day (New York, 1886), 133 and J. von Kries in Helmholtz's Treatise on Physio- logical Optics, tr. James P. C. Southall (Optical Society of America, 1925), III, 635f.

65 Ribot, German Psychology, 121. 66 Ibid., 126-127. 6 Ibid., 130.




seeing light for the first time 68 implied that human beings could do the same; spatial perception, therefore, was innate. Secondly, the nativist might argue that the empiricist's argument is logically incomplete. The empiricist explains visual spatial perceptions ultimately in terms of tactual data, i.e., we know what we see by touch. The nativist then asks: are not these primitive tactual representations innate? The upshot of one of psychology's dreariest chapters was that neither the empiricists nor the nativists had a clear field. The controversy over nativism and empiricism is as inconclusive as the controversy over the Molyneux problem, its XVIIIth century counterpart.

VII. OBSERVATIONS ON THE STUDY

Three general observations may be made on the preceding study. Let us first consider certain methodological issues involved in the attempts at verifying the Molyneux problem experimentally. That the reports on those who have acquired vision after operation for congenital cataract are not decisive seems well-attested. The reports were made by oculists untrained in avoiding leading and suggestive questions. The difference in the replies, dependent upon the pre- sumed intelligence of the patients, supports the contention that this is a factor. Furthermore, cataract cases are not usually totally blind; many of the cases involved patients who were not blind at birth, but had visual experiences of various degrees before the operation. For example, Parsons cites the evidence that an intelligent cataracted blind person is not entirely without visual experience. He may apply pressure to the nasal side of the eyeball producing a brilliant display of colors called the phosphene phenomenon, which is projected in space.69

Replies must be carefully evaluated because the verbal description is from a patient with experience totally alien to the oculist, who may as a result be interpreting the replies in the light of his own experience. Then too, the patient's eyes are sensitive and inflamed after the operation, and as Leibniz recognized, he may be confused at the time as well as being in considerable pain. As Carr says, " the data are somewhat ambiguous and indecisive in import." 70 The most authori- tative recent report concerning those who have acquired vision late in life is by Young. He writes in parts as follows:

68 See Bailey, Review of Berkeley, 151. Cf. also Abbot, Sight and Touch, 163- 173. For modern confirmation, see Vernon Grant, Psychological Optics (Chicago, 1938), 118. Grant, however, draws no conclusions concerning human vision. Mill, an avowed follower of Berkeley's theory of vision, recognized this as " the most serious difficulty which the theory of Berkeley has to face." Mill, Dissertations and Discussions, II, 110.

69 Sir John H. Parsons, An Introduction to the Theory of Perception (Cam- bridge, 1927), 158.

70 Harvey A. Carr, Introduction to Space Perception (New York, 1935), 1415. The account here of the difficulties involved in experimental verification of the issues is very much indebted to Carr.



408 JOHN W. DAVIS

During the present century the operation (i.e., cataract removel) has been done often enough for systematic and accurate reports to be collected. The patient on opening his eyes for the first time gets little or no enjoyment; indeed he finds the experience painful. He reports only a spinning mass of lights and colours. He proves to be quite unable to pick out objects by sight, to recognize what they are, or to name them. He has no conception of a space with objects in it, although he knows all about objects and their names by touch. . . . His brain has not been trained in the rules of seeing. ... For many weeks and months after beginning to see, the person can only with the greatest difficulty distinguish between simple shapes, such as a triangle and a square.71

Such contemporary evidence bears out the Leibnizian conception that the patient will be confused and unable to answer immediately. An even stronger point against the conclusiveness of the experimental evidence in answering the Molyneux problem is mentioned by the opthalmologist Murray:

... many people with normal sight fail to recognize an object in a bad light, or in unfamiliar surroundings, or in unusual positions.72

But that this evidence can be used to answer the Molyneux problem with a decisive negative seems doubtful. The reason is simply that the terms of the problem require an answer within a span of time too short for space perception to develop. If time is allowed for such space perception to develop, however, then the terms of the problem are changed radically. The answer, if an answer must be given, is to reject the problem as being unamenable to experimental test.

Two more general comments are in order. The controversy over the Molyneux problem provides a forum for the classic debate among the rationalists, the empiricists, and the sensationalists. According to their answers to the problem, their positions can be identified, and in a more definite manner than has hitherto been possible. Finally, the problem illustrates a phenomenon which has occurred more than once in the history of ideas -the shift of a problem from a speculative philosophical issue through a phase as a psychological problem to an ending as a problem for the physiologist. During its career, the problem undergoes such changes in its terms of reference that a definitive answer to the original question cannot be provided. It is doubtful, for example, if anyone who had taken up the rationalist or empiricist option would be unable to defend it on the basis of any facts or hy- potheses that might be alleged against it. This is not to despair of speculation, but to show the need for it as a stimulus to experiment and empirical inquiry.

University of Western Ontario. 71 J. Z. Young, Doubt and Certainty in Science (London, 1951), 61ff. (Italics

mine). 72 Michael Murray, " An Introduction to Bishop Berkeley's 'Theory of Vision,"'

British Journal of Opthalmology, 28 (1944), 606.



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