Rene Descartes · Philosophy
Descartes sought a single method, modelled on mathematics, to make all knowledge certain - and applied it to build a mechanical physics of a world of matter in motion, helping launch the Scientific Revolution.
Behind everything Descartes did lay a single, dazzling ambition: to find one method - a single way of reasoning - that could be applied to any subject and yield certainty everywhere. As a young man he had been struck by the contrast between mathematics, where reasoning is rigorous and conclusions command universal assent, and the rest of human inquiry, where opinions multiply and nothing is settled. Why, he wondered, should certainty be confined to mathematics? Perhaps the certainty of mathematics comes not from its subject matter but from its method - its way of starting from simple, self-evident truths and proceeding by clear, orderly steps. If so, that same method might be carried over to every field, making all of knowledge as certain as geometry. This is the unifying vision of Descartes’ life: a ‘universal mathematics’ (mathesis universalis) - a general science of order and measure, a single method of reasoning that could in principle settle any question the human mind is capable of settling. The method of doubt, the cogito, the proofs of God, the new physics, were all applications of this one method.
When Descartes turned his method to the physical world, the result was a revolutionary new picture of nature: the universe as a vast machine, made of matter in motion, governed by a few mathematical laws. Recall that the essence of body, for Descartes, is extension - being spread out in space. So the physical world is nothing but extended matter, divided into parts that move and collide. He banished from physics all the ‘occult qualities’, purposes, and substantial forms of the older Aristotelian science: stones do not fall because they ‘seek’ their natural place, and fire does not rise out of desire. There is only matter, shaped and moving, pushing other matter. Everything in nature - the orbits of planets, the tides, magnetism, the workings of plants and animal bodies - is to be explained mechanically, by the sizes, shapes, arrangements, and motions of material particles, according to universal laws of motion that God established at creation and conserves. This mechanical philosophy - nature as matter in lawful motion, with no purposes or souls in it - became one of the foundational ideas of modern science.
Descartes did not pursue certainty for its own sake alone; he had a practical, even utopian, vision of what a true science would do for humanity. The old, speculative philosophy of the schools, he complained, was useless - endless disputation that gave us no power over the world. But a true science of nature, built by his method on the mechanical understanding of matter in motion, would be enormously useful: by knowing the real causes of natural effects, we could harness them for human benefit. We could improve medicine and prolong life, develop better technologies, and in general make ourselves “the lords and masters of nature.” This is one of the founding statements of the modern project of science as power - the idea that the point of knowing nature is to control it for the relief of the human condition. It marks a decisive break with the ancient and medieval ideal of contemplation (knowing for the sake of knowing, or of beholding the divine order). For Descartes, as for Bacon, knowledge is for use; the new science promises not just understanding but mastery - health, comfort, and command over the forces of nature.
This is the opening of the lesson. The rest — the dialogue, the primary source, and the recall — is in the app.
You learned that Descartes sought one universal method, modelled on mathematics, and used it to build a mechanical physics of matter in motion. Explain his method and his mechanical picture of nature.
Leads to Francis Bacon.
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