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Synopsis of Alain Grosrichard, ‘Une Expérience psychologique au XVIIIe siècle’

[‘An Eighteenth-Century Psychological Experiment’]

CpA 2.3:99–113

This text, extracted from a diplôme d’études supérieures (equivalent to an MA thesis) that Grosrichard did under the supervision of Georges Canguilhem, serves at once as an introduction to the text that follows it - a lesson by the eighteenth-century Swiss philosopher and Berlin academician Jean-Bernard Mérian - and as a schematic history of the philosophical ‘problem’ that is the subject of Mérian’s lesson and which illuminates the inherent aporias of sensualist philosophy and empiricist psychology.

The problem in question is what is canonically referred to as ‘Molyneux’s problem’, a thought experiment which divided rationalist and empiricist philosophers, and which provided, in Michel Foucault’s words, one of ‘the great mythical experiences on which eighteenth century philosophy sought to ground its beginning’. In the seventeenth century, the Irish jurist and scientist William Molyneux wrote a letter to his friend and correspondent, John Locke, proposing the following:

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. Quaere, Whether by his sight, before he touch’d them, he could now distinguish, and tell, which is the Globe, which the Cube.1

Locke’s answer to this hypothetical was a categorical ‘No’, given that all knowledge had to come from experience. The blind man would have to experience the coordination of his sight and touch before he would recognize the correlation of the senses as viable. For Leibniz, by contrast, the answer was ‘yes’, as long as the blind man were informed that the objects before him were those he had just touched. Using his vision, the newly sighted man would in fact be able to distinguish the shapes by coordinating the visual features with the concepts in his mind that had been previously correlated uniquely to touch. Leibniz maintained that, were this not the case, i.e., were Locke’s position correct, this would mean the existence of two distinct geometries, one for sight and one for touch, a conclusion which Leibniz deemed absurd.

Molyneux’s question exercised thinkers throughout the eighteenth century, Berkeley, Condillac, and Diderot, chief among them. The hypothetical question itself acquired an apparently firmer base in 1728 when the surgeon William Cheselden successfully removed the congenital cataracts of a boy born blind. Later, when Voltaire publicized the results of this operation - the boy had severe difficulty coordinating his senses; he stubbornly refused to make use of his newly acquired gift - many philosophers believed that the doctrine of innate ideas had been empirically discredited.

The problem itself refused to go away, however, receiving one of its most sophisticated formulations in Diderot’s Lettre sur les aveugles, a text which built on Berkeley’s fundamental contention that the only possible link between sight and touch was one of association, the senses being incommensurable in themselves (Berkeley compared seeing what is touched to hearing scents or smelling sounds). Subtly changing the terms of Molyneux’s problem, Diderot replaced the globe and the cube with the circle and the square, thus eliminating the element of depth perception from the problematic. For Diderot, Molyneux’s problem, when framed in this way, put paid to any referential or denominational notion of language, in effect pointing to the primacy of the signifier over the signified. The only ‘problem’ for the newly sighted man would be the coordination of two arbitrary sign systems, that of his sight, and that of the words or concepts he had already come to associate with his sense of touch. Though one sense would ‘of necessity’ come to be the sign for the other, the necessity would be one inhering in the chain of signification itself, not in the relation of two distinct signs to the same referent.

The theoretical richness of Molyneux’s problem infuses Grosrichard’s compressed account, which is indebted both to Canguilhem, in that it identifies the political complicity of competing epistemologies, and to Lacan, in that it evinces a concern for the relations among desire, sight, knowledge, and truth. Though the role of signification in the history of Molyneux’s problem appears to inform Grosrichard’s piece, the main focus is on the historical transformation that takes place in the eighty years separating Locke and Mérian concerning the relation of philosophy to the experimental sciences, psychology in particular.

Whereas for Locke the theoretical goal was for the philosopher to ‘become blind’, i.e., to imagine himself as unable to see so that he might establish the truth content of his own discourse, for Mérian, like Diderot, the aim is for the blind to ‘become philosophers’. While not as well known to posterity as others concerned with Molyneux’s problem, Mérian went the furthest in articulating the conditions necessary for experimentally resolving the dispute and in arguing for their feasibility. Mérian proposed to raise children as ‘artificially blind’, keeping them in the dark from birth, providing them varying degrees of education and sensory exposure (apart from sight). At a certain age, they would be ‘made to see’, at which point the philosopher could then witness the putative resolution of the blockages in his own discourse and have its truth confirmed.

In the first section, Grosrichard sketches the ironic affinity between Cartesian rationalism and Lockean empiricism. Whereas the truth of Descartes’ discourse is guaranteed by an extrinsic God, Locke’s Essay attempts to establish the following: ‘all these ideas - supposedly innate, deposited there by the Other - are mine’ (CpA 2.3:102). In other words, the foundation of all truth must be in experience; knowledge is acquired, not given, and the distinction between description and acquisition is a false one. But Grosrichard identifies the aporia of Locke’s effort as follows: ‘It remains the case that, from the frontiers of the most obscure and confused Cartesian perception, the discourse of the Essay covers little by little, with neither rupture nor leap, the whole domain of Cartesian knowledge [savoir], ultimately reconnecting with the other frontier, the one that limited the domain of Cartesian understanding when faced with the divine infinite. Everything is acquired, from what used to be only on loan [prêté]. Everything, except the truth status of this everything [Tout, sauf la valeur de vérité de ce tout]’ (CpA 2.3:103).

It is this inability to establish its own truth content that at once undermines and motivates the discourse of empiricist philosophy. Grosrichard identifies the fundamental circularity that inheres in Locke’s gloss on Molyneux’s problem: the only way to confirm the truth of his discourse is to imagine that he does not already know it is true. Only then, will he ‘discover’ that what he thinks is, or indeed already was, true. For Locke, the testimony of the blind man made to see cannot be trusted in itself, since the blind are already corrupted by the prejudices of hearsay and other sensory experiences. In other words, their experience does not count as viable philosophical experience because it is already overly conditioned by experience. Maximizing the semantic content of the French expérience - meaning both ‘experience’ and ‘experiment’ - Grosrichard makes a case for the absolute lack of space in Locke’s discourse for anything like an ‘experimental psychology’ in the modern sense. The only ‘experiment’ that is needed is a thoroughly paradoxical ‘thought-experiment’, that is, the experience of the philosopher who imagines himself as being prior to experience so as to have the proper experience.

Grosrichard notes that the reason empiricist philosophy has no need for experimentation is because it takes its own model of subjective perception and pushes it all the way down, making it the ground of all truth and philosophy. The uniquely human soul ‘traverses the machinery of the body, to the external world’ in a fantasy of direct access. What changes in the early eighteenth century is the subject of Grosrichard’s next section, namely the introduction of the animal in the human. Once it is suggested that animals may have souls, the place of the animal ‘in’ the human becomes a philosophical and scientific problem. ‘The introduction, so to speak, of the animal in the human is, believe us, the possibility itself of psychology’ (CpA 2.3:107). Once perception is taken to be a physiological phenomenon, as opposed to a purely mental one, such as with Locke’s ‘blinded’ or voided subject of perception, then it can be an object of experimentation in a mechanical and material sense. Identifying a theme that will later be developed by Alenka Zupancic in an essay indebted to this one, Grosrichard finds in this moment an effort on the part of the experimental philosopher to effectively see sight itself. The use of microscopes allows scientists to look at optical fibres: ‘psychology can extrapolate from what the physiology of fibres gives it, leading analysis beyond a perception that is always already constituted for it’ (108). But this effort on the part of the understanding to see itself seeing generates a fundamental opacity or blind spot. ‘For dissecting the understanding in order to satisfy the demands of grounding knowledge and mastering its empire would no longer imply the dismantling of a judgment - necessary, but revocable - but rather the denial of its status as living’ (109).

Grosrichard identifies this tendency toward reduction, replacing reflective judgment with mechanistic genesis, in a famous sequence in Condillac’s Treaty on Sensations, wherein a hypothetical statue is progressively accorded human senses (cf. CpA 4.2:60). It is no accident, in Grosrichard’s reading, that ‘the immobile marble in a human form was substituted for Locke’s tabula rasa’ (109). In an effort to come to terms with Molyneux’s problem, Condillac proposes a manipulation of the variables and the techniques of knowledge itself, proposing that the blind man who is operated upon be confined to a glass cage, so that he might be a ‘pure sensible retina, the place wherein the petrified man meets the statue who animates him’ (110). A fundamental difference separates Condillac and Diderot. Where Condillac advises a manipulation of technique, it is Diderot who effectively inverts the Lockean problematic: ‘No longer capable of finding the born-blind in himself, the philosopher, in order to neutralize the subjectivity he needs, to see across it the visible in its purity, must make the blind man a philosopher, which is to say, exceedingly aware of the lacunae of his experience and master of his language’ (110).

For Grosrichard, this historical trajectory and the theoretical inversion it accomplishes results in the modern form of experimental psychology, a domain described as ‘the ensemble of techniques philosophy invents to keep its mastery over the space of the understanding’. In a sense, the goal was to develop a philosophically ‘experimental’ psychology that ceded nothing to the ‘seductive discourse’ of the ‘barbarians’ of a purely scientific psychology that undermined philosophy itself. The reason that Mérian’s seminar is presented as the culmination of this line is that it encapsulates the effort to think together two criteria which had before seemed exclusive: experimentation on the human, and keeping the human alive as a human. ‘To render children artificially - but provisionally - blind, is not to deny the human [l’homme], it is simply to go against an idea of the human born from popular prejudice: a prejudice which imputes to the human an essence that cannot be perfected’ (112).

In a conclusion infused with irony and pathos, and which evokes the cybernetic concerns of the post-war era, Grosrichard heralds the motivation subtending Mérian’s proposal. The goal is for the human to use all the reason at its disposal in order to perfect and transcend itself as a species. ‘Man perfects himself, because he is the product of the rational utilisation of what is in him by nature.’ More: ‘The techniques for knowing human nature [la Nature dans l’homme], which require and permit its dissection, permit in turn its recomposition according to a constructed order, which is no longer that of chance and habit, but of a nature ordered by reason. And because reason is the product of a natural progress in man, the order imposed by reason will be the true natural order. Man is served by what nature gives him in order to perfect his nature’ (112).

Grosrichard’s apparent endorsement of a new man along the lines dreamt of in Mérian’s experiment is tempered by several asides which evoke his thesis director’s remarks concerning the proximity of the Pantheon to the prefecture (CpA 2.1:91): ‘Mérian’s proposal, wherein the philosopher is the director (delegated by the sovereign) of a laboratory, which is also an establishment with a support centre, a hospital, school, and manufacturing wing, topped off with an Academy of philosophers, this is no doubt the product of a psychology which is still inseparable from its philosophy and for which knowing how man feels, thinks, and knows is indistinguishable from knowing how he must feel, think, and know - to be a good citizen’ (113). Grosrichard concludes with a reformulation of Canguilhem’s alternatives: ‘This study opened with a man who denied divine seeds. It closes by giving the floor to another who built and led a seminar. Who today is in the place of the philosopher who took the place of God, who is the tree?’ (113).

References to this text in other articles in the Cahiers pour l’Analyse:


English translation:


Primary bibliography:

  • Berkeley, George. Essay towards a New Theory of Vision (1709), publ. 1732.)
  • Mérian, Chevalier de. Histoire du problème de Molyneux: Huitième mémoire (CpA 2.4:115-122).
  • Condillac, Étienne Bonnot. Traité des Animaux (1755). Paris: Vrin, 1987.
  • ---. Traité des Sensations (1754). Paris: Fayard, 1984.
  • Diderot, Denis. Lettre sur les aveugles à l’usage de ceux qui voix (1749) et Lettre sur les sourds et muets à l’usage de ceux qui entendent et qui parlent (1751). Marian Hobson and Simon Harvey, eds. Paris: Flammarion 2000.
  • Leibniz, G.W.Nouveaux Essais sur l’entendement humain (1703), publ. 1765. Jacques Brunschvicg, ed. Paris: Flammarion, 1966.
  • Locke, John. An Essay concerning Human Understanding (1694), Peter H. Nidditch, ed., Oxford: Clarendon, 1975.
  • Mérian, J.B. Sur le problème de Molyneux, postface de Francine Markovits, ‘Diderot, Mérian et l’aveugle’. Paris: Flammarion, 1984.

Selected secondary sources:

  • Evans, Gareth. ‘Molyneux’s Question’ in Idem., Collected Papers. Oxford: Clarendon, 1985, pp. 364-399.
  • Foucault, Michel. Naissance de la clinique. Paris: PUF, 1963.
  • Jay, Martin. >Downcast Eyes: The Denigration of Vision in Twentieth-Century French Thought. Berkeley: University of California Press, 1993, Chapter Two: ‘Dialectic of EnLIGHTenment’, pp. 83-147.
  • Morgan, Michael J. Molyneux’s Question: Vision, Touch and the Philosophy of Perception. Cambridge: Cambridge University Press, 1977.
  • Paulson, William R. Enlightenment, Romanticism, and the Blind in France. Princeton: Princeton University Press, 1987.
  • Zupancic, Alenka. ‘Philosophers’ Blind Man’s Bluff’ in Renata Salecl and Slavoj Zizek, eds., ‘Gaze and Voice as Love Objects’. Durham and London: Duke University Press, 1996, pp. 32-58.


1. John Locke, An Essay concerning Human Understanding, Book II, Ch. 9, § 8