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Philosophy for the Blind

By Ciara Griffiths

To kick off Disability History Month, we journey to the Enlightenment in Paris, 1749. It is 9 o’clock on a summer’s morning. The French philosopher, Denis Diderot, is getting ready for a day’s work, when there are violent knocks on his door. The police have a warrant for his arrest. He is to be taken immediately to the Vincennes Prison on the charge of authoring an atheistic text. His Letter on the Blind for the Use of those Who Can See.

As a philosophy student, I have read many texts throughout history, but Diderot’s Letter has always stuck me. A lecturer mentioned it in passing so I decided to read it. I am glad I did. It is a short piece (by philosophy standards), but what it lacks in length, it makes up for in thought-provoking and poignant rhetoric. It is also one of the earliest known examples of disability appearing in philosophy. Before diving into this interesting story, I must first give some brief context to the philosophical debates of the Enlightenment.

In the Enlightenment, there were two main philosophical ideas: empiricism and rationalism. Rationalism is the belief that all our thoughts, emotions and ideas are based on reason. Innateness (ideas being born in us) and the idea of the soul are key factors. Empiricism is the belief that everything is based on experience, observation and experimentation. Rationalists and empiricists wrote essays, treatises and pamphlets to argue their points, but very few of them mentioned the disabled. This is not to say that the disabled were ignored in the Enlightenment: the European surgeons were developing new procedures to ‘cure’ blindness, but there was never a full text devoted to disability.

In 1739, the blind mathematician, Nicholas Saunderson, died. A decade later, Denis Diderot was making his debut as a philosophe. He had published a few works, but he was not wealthy. He was from a small town in the northeast of France. He was once destined for the Church, but after studying Philosophy at the University of Paris, he decided to become a writer.

After witnessing an eye surgery with his friend and learning about Saunderson, he became fascinated with the blind. His friend knew a blind man who lived outside of Paris and when Diderot asked if he could interview him, his friend accepted and took him to the blind man’s house. There was little on the blind in philosophy, so Diderot decided he would give them a voice.  

The meeting with the blind man is recorded in the Letter. I will not recall the whole thing, as I highly recommend reading it yourself. The blind man is never named, presumably for anonymity purposes. In summary, Diderot and his friend visited the blind man’s house at five o’clock and asked of his life, his aspirations and his outlook on society.

We learn in the introduction that the blind man was the son of a philosophy professor. In Paris, he attended natural history and chemistry lectures. Sadly, this was the eighteenth century and society – not in all cases, as we saw with Saunderson – was not as accommodating towards disabled people as it is now. The blind man was forced out of Paris, leaving him in a commune outside of the city with his blind son and wife. Despite this, the blind man is content, refusing to let his blindness dwindle his quality of life.

Saunderson had given Diderot an idea. The middle section of the Letter is devoted to a fictionalized account of Saunderson’s deathbed. Saunderson denounces God’s existence, for He has not revealed Himself in any form. He could not touch Him, feel His presence, or hear Him.  Therefore, He is not real. This is classic empiricism: only through sense experience can we know things. I am not here to justify or disprove Diderot’s claim, but this was Diderot publicly declaring his atheism. France was predominately Catholic, so for someone to denounce the legitimacy of the Church was the equivalent of sedition. He was imprisoned for three months.

It is hard to say what Saunderson thought of God, or what the blind man thought of the Letter. However, the Letter did set Diderot up for a successful philosophical career. For me, the most striking part of the Letter comes at the end, in which Diderot makes a plea to the scientists of the day. ‘Science should be equally advanced by questioning a sensible blind man’. In other words, instead of obsessing over experimental procedures for the sake of ‘enlightenment’, we should get to know the blind. I believe this plea is not just aimed at the scientists, but to all of Diderot’s readers. For him to say this in the eighteenth century is, to me, powerful. Perhaps this tells us something for our own time. We should get to know our disabled. Like the blind man in Diderot’s Letter, we might learn something, as Diderot and his friend did.

We can read Diderot’s Letter in three ways. We can read it like the French authorities did, as an atheistic text and a philosophe looking for trouble. We can read it as an empiricist essay that proves the value of sense experience. Or we can read it as a simple man talking to a blind man about his life. A statement of history, which contains a message to those of Diderot’s time and to those of our time. However you read it, it is something to think about.


Curran, A. S. (2020). Denis Diderot and the Art of Thinking Freely. Other Press, New York, USA

Diderot, D (1916) Diderot’s Early Philosophical Works. Translated and edited by Jourdain, M. Chicago and London Open Court Publishing Company