Letter about the blind, for the use of those who see

Image: Soledad Seville


Preface to the recently published reunion of two books by Denis Diderot


The idea that the two Letters by Denis Diderot gathered here form a pair depends almost exclusively on the sensorial reference contained in their respective titles, “about the blind”, “about the deaf-mute”. Many other things seem to separate them, starting with their style, demonstrative in the first, essayistic in the second. The exposition about the blind is agile and direct, it moves quickly towards its objective, passing through three characters drawn from real life – in fact four, if we count the appendix added later.

The discussion about deaf-mutes is slow and digressive, sometimes seems out of focus, has no characters, and leads into an appendix that, due to its length, threatens the formal balance of the text. While in the first letter, dated 1749, Denis Diderot chose a series of allies to support the controversial conclusions he reached, in the second, from 1751, he preferred to focus on his opponents. Both are experimental writings, as, in addition to not reaching definitive conclusions, they proceed from the examination of a repertoire of cases: blind individuals here, textual evidence there.

There are other obvious affinities when the letters are read together. The main one, I would like to suggest, is the clear idea that they paint, in the reader's imagination, of a new object, free, autonomous, active, endowed with its own rules: the living body, a materiality that emerges as pure sensation, which it exists by itself, it was not created, and is, to that extent, an indication that the very idea of ​​creation has become obsolete. This painting is masterfully done through a skillful combination of different perspectives, in the manner of Leibniz's monad.

The blind person who cannot see feels firsthand what escapes those with sight, and, as a result, has a different idea of ​​the much vaunted “order of nature”. The deaf-mute does not speak or hear, but gestures, his body is pure movement, a unit that configures and reconfigures the space around him. The perfect scheme of this integrated totality is the hieroglyph or ideogram. Just as the truth of vision is in touch – the eye feels the objects that affect it as physically as the skin –, that of speech is in the silent gesture, the first figuration of what Robert Bringhurst will call the “solid form of language”.[1]


Denis Diderot entered the history of philosophy as an erratic, rhapsodic thinker, incapable of producing a coherent system. In this assessment, two orders were confused, that of thought and that of exposition, which were inseparable for him: the elaboration of a coherent conceptual reflection, through an exposition marked by discontinuities of genre, form and style. If we had to determine the moment in which the fundamental elaboration gained momentum and direction, we would have to choose the Letter about the blind, for the use of those who see. The echoes of this text are found everywhere in the philosopher's later production, who, in 1782, recognized that, if he had to change the text, he would write another one, probably not as good. That is, despite imperfections in composition and style, the idea remains there, as the germ of everything that will come later, organically, from it.

The vitalist metaphor is appropriate, as one of the limiting experiences to which the blind have privileged access is, precisely, the approach of death, which they, for a series of reasons, fear less than the sighted. Everything happens as if the idea of ​​life itself gained a contour, in the analysis of sensations, not from the comfortable remission to a “vital principle”, but by determining the modes of relationship of the sensitive organism, in this case, taken from its human configuration.

Draws attention to Letter about the blind the perfect symbiosis between exposition and argumentation. The text is divided into three sections, elegantly arranged in the flow of writing, each of them dedicated to a blind individual that Diderot knew or encountered in literature, and which provides him with the complete illustration of one of the points that make up the argument (they are blind people who it makes it complementary). Nessa Menu With a provocative title, Diderot makes a point of being very clear to the addressee, Ms. Simoneau, and we, to whom he grants the privilege of reading, can only benefit from this quality.

The urban tone is perfect for enunciating a thesis with profound consequences, whose presupposition fully meets the pretensions of classical metaphysics. “In effect”, writes Gérard Lebrun, “the blind man forces the moralist or the metaphysician to confess that his philosophy is not the work of a rational subject, but the ideology of a living being who believes he has a relationship with things that we call vision. Using only his questions, the blind man puts us in the same position we would put a living being with several pairs of eyes – he makes us enter naively into the dimension of monstrosity”.[2]

Denis Diderot invites us to think of reason as a limited power, not in the sense of finitude, in contrast to the plenitude of divine reason, but of a constitutive trait of the human animal, which acquires or invents this or that metaphysics, depending on the full or partial use of the senses. The model extends to non-human animals, which have thus recognized an instinct for speculation that leads them to consider in experience solutions to the problems that sensation poses to them. From the outset, the claim of metaphysics to become a universal science, which would even be responsible for providing the rational foundation of religious belief, is undermined.

Denis Diderot's blind men are not abstract or neutral figures. In common, they have a partiality towards their own condition. They know they are different, but at the same time, they deeply feel strange about the way sighted people see the world and extract, from this experience, consequences that make no sense to the blind. It may seem surprising that a blind man is a geometrician and teaches this science at Cambridge University to sighted students. This astonishment is the result of naivety: geometry is not the language that God chose to enunciate the world, but a system of signs that describe sensitive relationships, which can be grasped and exposed by vision – which leads us to forget that its The ultimate foundation, as a description of space, is tactile relations.

In 1782, an unexpected addition: a small note, in which a fourth character is introduced, Mélanie de Salignac, a blind young woman whom Denis Diderot knew personally and who taught him, with refinement and precision, the autonomy and elevation of a metaphysics that, now it seems not only original, but also, in many ways, superior to that of the seers, and, to that extent, indispensable to it. More than a critical counterpoint, the blind girl's order is like the truth underlying that of the seeing reader.

The physiology of a blind woman is not like that of a blind man, and what she cannot see allows her to feel other things, which are not the same as what he feels. Less accustomed to reasoning, less permeated by abstract metaphysics, Mélanie opens Diderot's eyes to the sensitive relationships from which the human animal contemplates what philosophers like to call “nature” or “world”.

At this point, the philosophy reader might remember that, in classical metaphysics, the privileged mode of divine intuition is vision. Not content with naming God as the architect of infinite cities that overlap each other from different perspectives, Leibniz also guarantees, in Monadology, that “he who sees everything” in the universe “could read”, in each monad, “everything that happens everywhere and even what has been done and is about to be done”.[3]

With his blind men and his blind woman, Denis Diderot refuses to lament the finiteness of creatures who do not see everything, celebrating, on the contrary, the privilege of living beings who, because they do not see, understand that the idea of ​​a vision of the whole has never been more than an illusion. Therefore, the strange cosmology that Menu offers, at a certain point, a description, in words, of what the blind man's senses perceive, without, however, seeing anything.[4] It will be up to poetry – Diderot's models are Lucretius and Ovid – to fill the gap left by the obsolescence of metaphysics.


At first glance, the animal of this other Menu, about deaf-mutes, is not the same as the first one, which consumes sensation and regurgitates reflection. It's more like an animal that speaks, gestures, dances, sings, recites – in short, expressive. The problems of the text begin with the expression. As Franklin de Mattos says, the Letter about deaf-mutes “is not the easiest to read”, not because it is obscure, but because the author, who in Letter about the blind Having adopted a very elegant expository economy, he now prefers to conceal his purposes, piling up questions in front of a reader who, being so perplexed, may become exhausted.

A strategy that takes us to the heart of what is at stake, and which only comes to light at the end of the text, dedicated to poetry. Because, “what defines the 'spirit' of poetry is precisely the power to link several ideas to the same expression, that is, to transform successive speech into simultaneous language (into “hieroglyph” or “emblem”, as the saying goes). Menu). "[5] Recovering the link between language and sensation: an imperative that links this second Menu to the first, in which a certain system of signs – metaphysics – is disconnected not from sensations, but from the abstractions to which it was intended to give prominence.

Everything happens as if Letter about deaf-mutes demonstrate the thesis he defends regarding poetry inside out, linking a single idea, the physiological unity of the human spirit as the foundation of the arts, to a plethora of questions. How can we grasp something that is neither a metaphysical entity nor a physical reality, that cannot be reduced to the unifying power of the concept? Moving nimbly on the surface of the modes of expression, Diderot diverts us at every moment from the shortcuts that could lead us to the stabilization that is consummated in understanding. It thus expresses the strength inherent in sensation, which gives the thought, which derives from it, a dynamic different from the contemplative capacity of the Cartesian soul and even the affective serenity of the Spinoza body.

Taken by many as a small treatise on aesthetics, as a minor writing, the Letter about deaf-mutes carries out a review of the precepts of rhetorical composition, thus arriving at a poetics that Diderot himself would apply to his reflections on dramatic art (which he himself contributes to renewing) and to the exercises of description that punctuate the strange “art criticism ” undertaken in Salons. In these reflections, the prominent place given to beauty by French treatises, an apparently neutral concept that, however, as shown by the Letter about the blind, depends on a very partial conception of human sensitivity. From now on, it is not up to the artist, using words, sounds or images, to imitate nature and, by purifying it, arrive at beautiful nature – a task that, we now know, is closely linked to the prejudices of theism. His task is different: to signify what the sign allows.

This conceptual reorganization entails a redefinition of art itself, which loses its intellectual status and becomes a physical experiment, from the sensation of the painter, sculptor or writer, who handles his materials and constructs an idea with them, to that of the spectator, transformed by the experience of direct physical contact with these constructions or “machines” that are artistic objects. Denis Diderot was never a painter or poet, and his philosophical dramas were written in prose.

The word translates sensation and modulates passion: it is a sign of what, in turn, signifies it. The idea of ​​order, criticized in the other Menu, is now renewed: unlike Nature, which poses and makes itself, speech becomes, in the hands of the philosophical writer, the illustration of the unity of the spirit that produced it, and which, we now know, is pure activity, or energy.[6] If each genre of art has its own object, which it does not share with the others, they all have this same sensuality that defines the artistic experience, located in the broader scope of sensorial experience. Art does not imitate nature, which is not beautiful; formalizes an experience, of sensation, which, in its raw state, contains the elements necessary to produce the most intense pleasure.


Years later, we will find the philosopher wandering through the galleries of the Louvre, in the annual exhibitions dedicated to young painters (the famous “Salons”), covering his ears with his hands to better hear the paintings, tempted to touch with his hands canvases that his eyes they already touch, and finding, in the colors of Chardin's paintings, the very substance of the things imitated.[7] The artistic object, manufactured by the skillful intelligence of the painter or sculptor, becomes the occasion for a singular experience, sharpening perception, refining sensation and intensifying pleasure. Contemplation is defined as a sensorial experience that mobilizes the spectator's entire body, similar to what was done with the artist's.

Writing about these works requires the author to have control over these elements and know how to transform them into determined signs, written characters, that can produce, in the reader's mind, the suggestion of the images he describes or to which he alludes. The contours blur, beauty is elevated to the power of the sublime, representation is reduced to the active and vital feeling that first makes it possible.

In the entry “Composition”, written for Encyclopedia and published in 1753, two years after the Letter about deaf-mutes, Diderot elaborates an interesting reflection, which allows us to measure the distance that separates his poetics from that of French classicism, with which, however, he still does not completely break.[8] As my colleague Luís Nascimento, who died prematurely in 2022, observed in a text that remains unpublished, a large part of the entry is a paraphrase of Shaftesbury's book, “Conception of the historical framework of the trial of Hercules”, in which the English philosopher examines the moment exact option to be chosen by a painter who wants to represent on canvas the story of Hercules' choice between pleasure and virtue.[9] It is a recurring theme in pictorial iconography, and, if Shaftesbury takes it up again, it is in an attempt to show that, if the precepts of drawing and plastics, which traditionally guide representation, are so important, it is because the transmission of a message depends on them. moral.

The moralizing character of painting is a recurring topic in Salons, and it is no wonder that Denis Diderot has explored it since 1753. However, we must not forget the final part of the entry, where Diderot risks extending Shaftesbury's considerations to the representation of another scene of a moral nature, Alcibiades' entry into Socrates' banquet , as it occurs in Plato's dialogue of the same name. It would be better to talk about displacement, because now the heroic and civic virtue of Shaftesbury's Hercules gives way to a loving and erotic virtue, in which the body's forces – say, its physiological capacities, so well explored in the letters – are directed towards the performance of acts of pleasure, which, except in exceptional cases, do not imply exhaustion. Physical sacrifice, replaced by surrender, ceases to be the condition for the elevation of a soul, which becomes a metaphor for a particular sensorial condition to which Diderot gives the name “self”.[10]


As Letters by Denis Diderot were published at a time – the turn of the 1740s to the 1750s, in the so-called “Century of Enlightenment” – that saw an important turnaround in the world of European letters. Until then, French philosophy had been content to contest, more programmatically than conceptually, the Cartesian legacy that weighed on spirits. The Philosophical Letters, written from England by the young Voltaire and published in 1726, tried to open the eyes of their compatriots to the English revolution, caused by Newton's physics, Bacon's experimental method, Locke's sensualist philosophy. This manifesto paves the way not only for the later developments of Voltaire's philosophy, but also for the adaptation, by the new generation, of island methods to the continental way of thinking.

The abundance of references to the English in the Letter About the Blind shows that Diderot, Shaftesbury's translator, remains a resolute Anglophile. Among the French, he highlights, in addition to Voltaire, Condillac, author of a Essay on the origin of knowledge (1746) and a Treaty of systems (1750), with which the Menu, although it does not express strict agreement, is strategically aligned. That entente, forged some time ago in weekly meetings at the café La Coupole, in which Rousseau also participated, lasted a short time. As Treatise on sensations, from 1754,[11] Condillac moves away from his mentor Locke and resumes Letter about deaf-mutes, but keeps the investigation in an intermediate zone between metaphysics, grammar and physiology. Diderot accuses him of plagiarism; the friendship falls apart forever.

In the review of Treatise on sensations written by Grimm for Correspondence littéraire, a periodical that circulates in a limited edition in the high circles of European courts, Condillac's book, although it receives praise, is compared unfavorably to Diderot's. Almost three hundred years later, we understand that these rivalries hide a precious secret, of a polymorphic work, woven collectively, that forms a legacy – of the Enlightenment – ​​with which every now and then we are forced to settle accounts. Rediscovering texts, gaining a taste for detail, falling in love with filigree, there are so many ways to avoid generalizations and thereby renew the exercise of criticism – almost always exhausting, usually rewarding. Denis Diderot's voice, expressed with such vivacity in the Letters, can be a guide for those who want to dedicate themselves to carrying out this task.


This volume brings together, for the first time in Portuguese, the two Letters, offering them in new translations, written by scholars more than familiar with the writings of Denis Diderot. The reader will also find two complementary documents, the entry “Cego”, written by d'Alembert for the Encyclopedia (v.1, 1751), actually a critical review of the Letter about the blind, as well as the review of the Treatise on sensations, written by Grimm, as we said, for the Correspondence littéraire, which includes an apology for the Letter about deaf-mutes.

*Pedro Paulo Pimenta He is a professor in the Department of Philosophy at USP. Author, among other books, of The fabric of nature: organism and purpose in the Age of Enlightenment (unesp).


Dennis Diderot. Letter about the blind, for the use of those who see e Letter about deaf-mutes for use by those who hear and speak. Translation: Franklin de Matos, Maria das Graças de Souza, Fabio Stieltjes Yasoshima. São Paulo, Editora Unesp, 2023, 232 pages. [https://amzn.to/48b5nCu]


[1] Robert Bringhurst, The solid form of language. Trans. Juliana A. Saad. São Paulo: Edições Rosari, 2006.

[2] Gérard Lebrun, “The blind man and the birth of anthropology”, in: Philosophy and its history. São Paulo: CosacNaify, 2006, p.55.

[3] Leibniz, “Monadology”, 61, in: Discours de métaphysique suivi de Monadologie. Ed. Laurence Bouquiaux. Paris: Tel-Gallimard, 1995, p.197.

[4] See Maria das Graças de Souza, Nature and illustration. About Diderot's materialism. São Paulo: Editora Unesp, 2002, chap. 1.

[5] Franklin de Mattos, “As a thousand mouths of sensation”, in: The philosopher and the comedian. Belo Horizonte: UFMG, 2004, p.158.

[6] Michel Delon, L'Idée d'energie au tournant des Lumières. Paris: PUF, 1988, p.74-84.

[7] See Jacqueline Lichtenstein, La Tache aveugle. Essai sur les relations de la peinture et de la sculpture à l'âge moderne. Paris: Gallimard, 2003, chap. two.

[8 ]See in the original v.3, p.772-4, and, in the Brazilian edition, v.5.

[9] Shaftesbury, “A Notion of the Historical Draught of the Judgment of Hercules”, in: Second Characters, or the Language of Forms. Ed. Benjamin Rand. Bristol: Thoemmes Press, 1995.

[10] See Georges Vigarello, The feeling of self. History of body perception. Trans. Francisco Morás. Petrópolis: Vozes, 2016, chap. 3.

[11] Condillac, Essay on the origin of human knowledge. Trans. Pedro Paulo Pimenta. São Paulo: Editora Unesp, 2016; It is Treatise on sensations. Trans. Denise Bottman. Campinas: Editora Unicamp, 1994.

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