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Molyneux's Problem
Marjolein Degenaar
& Gert-Jan Lokhorst
William Molyneux (1656-1698)
On 7
July 1688 the Irish scientist and politician William Molyneux (1656-1698) sent a
letter to John Locke in which he put forward a problem which was to awaken great
interest among philosophers and other scientists throughout the Enlightenment
and up until the present day. In brief, the question Molyneux asked was whether
a man who has been born blind and who has learnt to distinguish and name a globe
and a cube by touch, would be able to distinguish and name these objects simply
by sight, once he had been enabled to see.
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As is apparent from both his writings and his lectures, Molyneux was highly
interested in optics and in the psychology of sight. To some extent this simply
reflects the general attitude of his time: optics was a subject that was then
engaging the attention of a number of leading scientists. His interest also had
a more personal background, however, for his wife had lost her sight in the
first year of their marriage. The immediate cause of his formulating the problem
and sending it to Locke is to be found in Locke's French extract of An Essay
Concerning Humane Understanding, published in 1688 in the Bibliothèque
Universelle & Historique. In this extract Locke distinguished between ideas
we acquire by means of one sense and those we acquire by means of more than one
sense. He maintained that someone who lacks a sense will never be able to
acquire the ideas pertaining to it. A blind man, for example, will never be able
to have any idea of colour. Among the ideas we are able to acquire by means of a
combination of senses, Locke reckoned those of space, rest, motion and figure. Molyneux's problem had to do with the last of these. Molyneux was probably
inspired by Locke's exposition of the ideas of persons born blind and the ideas
which can be acquired by means of both sight and touch. He was, moreover, a
great admirer of Locke.
On Saturday 7 July 1688 William Molyneux wrote a letter to John Locke setting
out for the first time his problem concerning the person born blind:
Dublin July. 7. 88
A Problem Proposed to the Author of the Essai
Philosophique concernant L'Entendement
A Man, being born blind, and having a Globe and a Cube, nigh of the same bignes, Committed into his Hands, and being taught or Told, which is Called
the Globe, and which the Cube, so as easily to distinguish them by his Touch
or Feeling; Then both being taken from Him, and Laid on a Table, Let us
Suppose his Sight Restored to Him; Whether he Could, by his Sight, and
before he touch them, know which is the Globe and which the Cube? Or Whether
he Could know by his Sight, before he stretch'd out his Hand, whether he
Could not Reach them, tho they were Removed 20 or 1000 feet from Him?
If the Learned and Ingenious Author of the Forementiond Treatise think
this Problem Worth his Consideration and Answer, He may at any time Direct
it to One that Much Esteems him, and is,
His Humble Servant
William Molyneux
High Ormonds Gate in Dublin. Ireland
For reasons unknown Locke never replied to the letter. However, a couple of
years later, after the two men had started an amicable correspondence, Molyneux
returned to his problem. This time with success. In his letter, dated 2 March
1693, Molyneux presented Locke with his problem, though in a somewhat altered
form, asking Locke if he could perhaps find some place in his Essay to
say something about it. This time Locke reacted with enthusiasm: "Your ingenious
problem will deserve to be published to the world." From the second edition of
his Essay (that of 1694) Locke included Molyneux's problem in his work
and thereby made it accessible to a wider audience:
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 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. Qaere, Whether by his sight, before he touch'd them, he could now distinguish, and tell, which is the Globe, which
the Cube.
In this formulation Molyneux's problem attracted the attention of lots of
philosophers and other men of learning, such as Berkeley, Leibniz, Voltaire,
Diderot, La Mettrie, Helmholtz and William James. In which ways did they
approach the problem?
In the first instance, philosophers considered it to be impossible that a man
born blind should be able to acquire sight. They regarded Molyneux's problem as
a kind of thought-experiment, which was to be dealt with by ratiocination alone.
The arguments put forward were usually concerned with the relation between
visual and tactual sensations or between visual and tactual notions of the form
of objects.
All these philosophers assumed that the visual and tactual sensations of an
object differ from each other, but there was no agreement concerning the
relation between the two. Some, Berkeley for instance, believed that this
relation is arbitrary and based only on experience. Others, such as Lee and
Synge, thought that it is necessary and perceived directly, while yet others,
such as Molyneux and Locke, thought that it is necessary and learned by
experience. Opinions were also divided concerning the relation between visual
and tactual notions of objects. Some philosophers defended the position that the
visual and tactual notions of a globe differ from one another, and can only be
related by either experience or reason (the latter view was defended by Reid).
Others believed that the visual and the tactual notion of a globe are actually
the same, or have something in common which is either observed directly
(Boullier and Hutcheson) or inferred by reason (Leibniz).
Investigating how the different positions correlate with the answers given to Molyneux's question, one can conclude as follows. Empiricists such as Molyneux,
Locke and Berkeley answered in the negative. More rationalist philosophers such
as Synge, Lee and Leibniz gave an affirmative answer. There was no unanimous
solution, amongst others because Molyneux's problem was interpreted in different
ways. Some philosophers thought that the man born blind had to answer directly,
while others were of the opinion that he should be able to make use of his
memory and reason, and that he should be at liberty to view all sides of the
objects by walking around them. Some philosophers believed that the question
implied that the man should be told in advance that he would be presented with a
globe and cube, whereas others thought that he should not be provided with this
information.
Discussion concerning Molyneux's problem took a new turn once the English
surgeon and anatomist William Cheselden (1688-1752) published an account of what
a congenitally blind person had seen after his cataracts had been removed
(1728). The publication led philosophers to regard the Molyneux problem no
longer as a simple thought-experiment, but as a question which could be answered
by experimentation.
In his account, Cheselden noted that when the boy was first able to see, he
did not know the shape of a thing and could not recognize one thing from
another, regardless of how different in shape or magnitude they were. Some
philosophers thought that Cheselden's observations were unequivocal and that
they confirmed the hypothesis that a blind man restored to sight would not be
able to distinguish objects and would have to learn to see. Most of these
philosophers, we might mention Voltaire, Camper and the elder Condillac as
examples, were adherents of Berkeley's theory of vision, which had predicted a
similar outcome.
Others, however, such as La Mettrie and Diderot, regarded Cheselden's account
as wholly ambiguous in its implications. They pointed out that it was possible
that the boy had been unable to make valid perceptual judgments because his eyes
had not been functioning properly. They suggested that this could have been due
to the fact that his eyes had not been used for a long time, or to their not
having had enough time to recover from the operation. They pointed out that Cheselden had, perhaps, asked the boy leading questions. Some philosophers also
believed that the results of the inquiry depended on the intelligence of the
patient.
Those who criticised the significance of Cheselden's account in this way
(most of them were French philosophes) made proposals as to how to
avoid the problems mentioned. They suggested that one should prepare the patient
carefully for the operation and for the interrogation, that one should allow his
eyes time to recover from the operation and that one should give him the
opportunity to exercise his eyes in darkness. What is more, one should avoid
asking leading questions.
Some philosophers were even more radically critical of operations like that
performed by Cheselden. Mérian, for example, noticed that Cheselden's
observations, like all observations of blind people whose cataracts have been
extracted, present difficulties because cataracts do not cause complete
blindness and complete blindness cannot be cured. It could not be concluded from
this that Molyneux's problem could not be solved experimentally, however, for it
could be maintained that patients operated upon for cataracts are directly
relevant to the solution of it. They are unable to perceive form before they are
operated upon, and the essential issue at stake when posing Molyneux's problem
is the ability to distinguish and name forms. This is a point of view which was
taken by many philosophers.
About 1800 several developments occurred which justify the speaking of a new
period in the history of Molyneux's problem. New accounts of patients operated
on for cataracts were published, and shed fresh light on the issue. Whereas Cheselden had only noticed what his patient observed in more or less natural
circumstances, later ophthalmologists performed experiments which showed whether
their patients were able to see form, size, distance, etc. Some, such as Franz
and Nunneley, were especially interested in Molyneux's problem as such, and
performed experiments with the prescribed globe and cube. Some of the reports
were in agreement with that of Cheselden, others conflicted with it. The cases
could not easily be compared, however, since the pre- and post-operative
circumstances differed to such a great extent. As one might have expected, an
extended scale of possible solutions to the Molyneux problem was brought under
consideration.
What is more, specialists also began to consider observations concerning the
sight of newly born animals and babies when discussing Molyneux's problem. Some
of those doing research in the field, such as Adam Smith and Johannes Müller,
supposed that the sight of young animals could be compared with that of a person
who had been made to see. The fact that certain animals see objects at a
distance as soon as they are born suggested that Molyneux's question could be
answered affirmatively. This turned out to be a strong argument against
Berkeley's theory of vision. Others, Thomas Brown for instance, were of the
opinion that the visual behaviour of babies could be compared with that of a
blind person who had been operated upon and made to see. They were convinced
that in both cases seeing has to be learned, and that Molyneux's question had,
therefore, to be answered in the negative.
Wheatstone's discovery that the perception by sight of the third dimension of
space is immediate, was used as a reason for answering Molyneux's question
affirmatively. The discovery was also regarded as disproving Berkeley's theory
of vision.
The data concerning the sight of patients who had been operated upon for
cataracts, and of young animals and infants, were used as evidence in the debate
concerning the question of whether the perception of space is innate or
acquired. Although Molyneux's problem was frequently discussed in this debate,
there was still no agreement on the right solution to it.
During the course of the twentieth century, the main interest in Molyneux's
problem has been historical. Biographers and commentators dealing with
well-known philosophers have analysed the solutions they proposed for it. Molyneux's problem has also turned up frequently in textbooks and general
histories of psychology, ophthalmology, neurophysiology, etc. A few authors have
written brief and incomplete histories of the problem. Degenaar (1996) has
written a comprehensive survey of the history of the discussion about Molyneux's
problem. Riskin (2002) described Molyneux's problem in the wider context of the
Enlightenment.
Philosophers, psychologists and other scientists have also tried to solve the Molyneux problem by making use of alternative approaches, both old and new. They
have, for example, made use of various accounts of recovery from early
blindness. As was to be expected, these proved to be as problematic and
inconclusive as were their predecessors in the eighteenth and nineteenth
centuries.
The Molyneux problem has also been tackled by methods more amenable to
experimental control than is possible in clinical studies, namely by rearing
animals in darkness. Visual deprivation experiments have shown that during the
development of the visual system there is a certain critical period in
connection with the presentation of light patterns. During this period, changes
brought about by deprivation can be reversed. If exposure to light is postponed
for too long, however, the development of normal visual mechanisms will be
extremely difficult, if not impossible. Although the results of deprivation
experiments are not relevant to the solution of Molyneux's problem—Molyneux
supposed that his blind man had a good visual system, whereas that of deprived
animals is abnormal—they have been used as evidence for Locke's position.
A recent approach to Molyneux's problem involves the use of sensory
substitution devices, developed in the context of corporeal mobility or reading
(Morgan, 1977). Learning how to use sensory substitution systems has been
considered a good approximation to Molyneux's problem, since such systems
present information normally handled by one modality, such as vision, to another
sense, typically audition or touch, using forms of coding novel to the user.
Experiments with sensory substitution systems show that subjects need some time
to learn to distinguish and identify objects, and this has been interpreted as a
confirmation of the position of Molyneux and Locke. Some researchers have
stressed the fact that a sensory aid is not, strictly speaking, a new modality,
and that to learn to use such devices is only an approximation to Molyneux's
problem, depending as it does upon the raising of similar issues.
Another variation of Molyneux's problem was suggested by Evans (1985). He
wondered whether the visual cortex of a patient with congenital blindness could
be electrically stimulated in such a way that the patient experiences a pattern
of light flashes (phosphenes) in the shape of a square or circle. This question
has been investigated experimentally, but the results do not provide a final
answer to Molyneux's question (see Jacomuzzi, Kobau and Bruno 2003 for
discussion).
There is one author who believes that no new approach is necessary: Gallagher
(2005, ch. 7) argues that developmental psychology and neurophysiology have
progressed sufficiently far to enable us to answer Molyneux's question once and
for all. He claims that Locke was right, but for the wrong reasons. However, it
remains to be seen whether this will be the last word.
The history of the issues surrounding Molyneux's question shows that the
question was not as easy to answer as Molyneux himself may have assumed. On the
contrary, there is no problem in the history of the philosophy of perception
that has provoked more thought than the problem that Molyneux raised in 1688. In
this sense, Molyneux's problem is one the most fruitful thought-experiments ever
proposed in the history of philosophy, which is still as intriguing today as
when Molyneux first formulated it more than three centuries ago.
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Cheselden, W., 1728, “An Account of some Observations made by a young
Gentleman, who was born blind, or lost his Sight so early, that he had no
Remembrance of ever having seen, and was couch'd between 13 and 14 Years of
Age”, Philosophical Transactions, 402: 447-450.
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Degenaar, M.J.L., 1996, Molyneux's Problem: Three Centuries of
Discussion on the Perception of Forms, Dordrecht: Kluwer Academic
Publishers.
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Evans, G., 1985, “Molyneux's Question”, in Gareth Evans: Collected
Papers, A. Phillips (ed.), Oxford: Clarendon Press.
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Gallagher, S., 2005, How the Body Shapes the Mind, Oxford:
Clarendon Press.
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Jacomuzzi, A.C., Kobau, P., Bruno, N., 2003, “Molyneux's question redux”, Phenomenology and the Cognitive Sciences 2: 255-280.
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Locke, J., 1688, “Extrait d'un Livre Anglois qui n'est pas encore
publié, intitulé Essai Philosophique concernant l'Entendement, où
l'on montre quelle est l’étenduë de nos connoissances certaines, & La
manière dont nous y parvenons”, Bibliothèque Universelle & Historique,
8: 49-142, Amsterdam: Chez Wolfgang, Waesberge, Boom, et Van Someren.
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Locke,
J., 1693, Letter to William Molyneux, 28 March, in
The
Correspondence of John Locke (9 vols.), E.S. de Beer (ed.), Oxford:
Clarendon Press, 1979, vol. 4, no. 1620.
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Locke,
J., 1690, An Essay Concerning Humane Understanding, London,
printed by Eliz. Holt, for Thomas Basset. Second edition 1694. Fourth
edition 1700, edited with an Introduction by P.H. Nidditch, Oxford:
Clarendon Press, 1975.
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Molyneux, W., 1688, Letter to John Locke, 7 July, in
The
Correspondence of John Locke (9 vols.), E.S. de Beer (ed.), Oxford:
Clarendon Press, 1978, vol. 3, no. 1064.
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Molyneux, 1693, Letter to John Locke, 2 March, in
The Correspondence of
John Locke (9 vols.), E.S. de Beer (ed.), Oxford: Clarendon Press,
1979, vol. 4, no. 1609.
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Morgan, M.J., 1977, Molyneux's Question: Vision, Touch and the
Philosophy of Perception, Cambridge: Cambridge University Press.
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Riskin, J., 2002, Science in the Age of Sensibility: The Sentimental
Empiricists of the French Enlightenment, Chicago and London: The
University of Chicago Press.
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Senden, M. Von., 1932, Raum- und Gestaltauffassung bei operierten
Blindgeborenen, Leipzig: Barth. Translated by P. Heath: Space and
Sight: The Perception of Space and Shape in the Congenitally Blind Before
and After Operation, London, Methuen, 1960.
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Simms, J.G., 1982, William Molyneux of Dublin: A Life of the
Seventeenth-Century Political Writer & Scientist, Blackrock: Irish
Academic Press. Edited by P.H. Kelly.
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19.Jan.09
Publicado por
MJA
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