Sophie's World

"I used Sophie’s World as an example because it’s such a wonderfully gentle introduction to that classical modern period. Jostein Gaarder starts with the Greek philosophers, but for me the book is most powerful when Sophie is learning about the classical modern philosophers. And if you ever try to read Kant, if you ever try to read The Critique of Pure Reason , you’ll understand why it’s good to learn about Kant’s philosophy another way. Einstein read it at the age of 13. Well, I’m no Einstein. I’ve tried to read The Critique of Pure Reason and it’s hard going and not everybody agrees how to interpret it. Sophie’s World is a wonderful introduction to ideas amongst these philosophers about the nature of reality, about what we can hope to know about the nature of epistemology, the nature of ontology, things in themselves, metaphysics. It’s a really, really nice way to get to grips with what some of these great philosophers were saying about the world. Then you can start to talk about how that leads into physics and, in particular, quantum mechanics. It’s also true of Newton. I’ve got a very good friend who’s a philosopher, based in New York, who says the reason that Descartes is considered a philosopher and Newton is considered a scientist is because Descartes got the physics wrong. I find it fascinating. When you look very hard at Descartes’s cosmology, his understanding and his description of the universe, there were certain principles that we would regard today as being scientific. For example, you can’t have forces that act at a distance in Descartes’s cosmology. If something’s going to be moved, then something needs to move it. There needs to be a contact or a collision or whatever it might be. Leibniz, Newton’s archrival–who is also regarded as a philosopher, not as a scientist—also pushed back on notions that were effectively built in and intrinsic to Newton’s classical mechanics. Newton had figured out that he could devise three laws of motion and a law of universal gravitation by assuming some things that other philosophers regarded as absurd and metaphysical. So absolute space and time—the idea that the universe is effectively infinite—is intrinsic to Newton’s three laws of motion. And of course Newton’s law of universal gravitation is action at a distance. Somehow there’s a force exerted between them that holds the Moon in orbit around the Earth. How was that supposed to work? Newton had no idea. What he did have, though, was a set of mathematical structures that were undoubtedly better than anything that had gone before. Descartes was, in many ways, more a scientist, wanting to adhere to scientific principles, than Newton was. Newton was prepared to accept some metaphysics, things you can’t explain or prove through evidence, because he got a set of principles that were really quite powerful and worked really well. There was more metaphysics in Newton than there ever was in Descartes. And we regard Newton as a scientist and Descartes and Leibniz as philosophers. It’s this really strange contradiction."