Denis Diderot
Gather all human knowledge in the Encyclopédie.
Denis Diderot (1713 – 1784, France) : enlightenment and materialism. Everything is explained by matter in motion. Matter can feel, and thought arises from organised matter: no need for a separate soul, nor for a God to explain the order of the world. On AskPhilosophy: 4 reconstructed arguments, 5 quotes checked word for word against the original texts, and 3 common beliefs examined; every text carries an authenticity badge (written by the author, posthumous, student notes, reported, apocryphal).
Why he matters
For more than twenty years he edited the Encyclopédie, the great project of the Enlightenment. His Letter on the Blind imagines, a century before Darwin, that badly formed beings die out and only those able to survive and reproduce remain. D'Alembert's Dream is one of the first texts to say that thought comes from living matter.
His times
The son of a cutler from Langres, he lived on translations before the Encyclopédie. His Philosophical Thoughts were condemned to be burned (1746). The Letter on the Blind cost him about a hundred days in prison at Vincennes (1749). After that he published anonymously, under a false name, or not at all: many of his masterpieces appeared only after his death.
His positions
click a row to see the evidenceA deist in 1746 (the order of nature proves God), an atheist and materialist from about 1749, according to most readers. But he never says so in his own name in a signed book: he has Saunderson or "Crudeli" say it, or writes it in texts published after his death.
Our ideas, even the most abstract, depend on our senses and the shape of our body: a blind man does not have the same metaphysics or morality as we do.
Doubt is the first step towards truth, and each mind sees through its own glasses. But this doubt serves enquiry: he trusts observation and experiment.
There is only one substance: matter. Sensitivity is a property of matter, and thought comes from organised matter. He says so under his own name, but in a dialogue published 46 years after his death.
Each of our actions is the necessary effect of what we are: free will is an illusion. The physician Bordeu says it in the Dream, but Diderot defends the same idea elsewhere.
There is a morality common to all nations, grounded in human nature. But many "virtues" are mere conventions, often religious, which contradict nature.
Reason is our only light; asking us to sacrifice it to faith is asking us to blow out our candle in the forest.
The world is "a momentary order", with no purpose written in advance. Saunderson says it; our texts on what Diderot puts in its place (virtue, posterity) are not yet collected.
One can be born taking pleasure in doing good, and education can strengthen this inclination. It is mostly bad laws that make people wicked.
No one has received from nature the right to command: legitimate power comes from the consent of the people, and it has limits.
Good is what has more advantages than drawbacks; "virtue" should become "beneficence". An ethics focused on the effects of our acts on others, close to utilitarianism, but also fed by feeling.