Jed Buchwald on Isaac Newton, Thomas Kuhn and How Science Really Progresses

High-Level Overview

Lex Fridman talks with Jed Buchwald, a historian and philosopher of science at Caltech who began his career as Thomas Kuhn's research assistant more than 50 years ago. The conversation opens with big questions about how science progresses, whether a theory of everything is possible, whether we can ever truly know reality, and where consciousness fits in a materialist view. It then settles into a rich portrait of Isaac Newton: his lonely childhood, his prism experiments, his feud with Robert Hooke, the invention of calculus and the priority dispute with Leibniz, the Principia, his work at the Royal Mint, his alchemy and his unusual religious views, ending with a thought experiment about bringing Newton forward in time to meet Einstein.

The tone is relaxed, curious and often playful, with Fridman asking self-described "absurd" questions and Buchwald answering with dry wit and deep historical detail. The conversation moves between philosophy of science, vivid historical storytelling and reflections on genius, competition and how experiments actually get done.

The Discussion Explores:

• Why Buchwald disagrees with Kuhn's neat picture of paradigm shifts
• The wave theory of light as a case study in how new theories win by enabling new work
• Lone geniuses versus communities, and the limits of a theory of everything
• Realism, perception and why colors are "in us," not in the world
• Newton's prism experiment and the craft of manipulative experimentation
• Hooke, Hevelius, Leibniz and the role of rivalry and jealousy in science
• Newton's life: childhood, the plague years, the Principia, the Mint, alchemy and religion
• How data was handled before statistics, and what Newton would make of Einstein

Deep Dive into Main Ideas

Beyond Kuhn's Paradigm Shifts

Buchwald explains that he left physics for history after becoming Thomas Kuhn's research assistant around 52 years ago and knew him well for decades. Kuhn's The Structure of Scientific Revolutions (1962) described scientists working within a paradigm, solving puzzles until anomalies accumulate and a new framework takes over. Buchwald believes paradigms exist but that change rarely happens so neatly in response to new experimental observations; today historians describe science more as a craftsman-like practice.

His key example is the wave theory of light, which Kuhn used as a paradigmatic case. Buchwald, who wrote a book on its origins, says the story was different: the Newtonian particle theory could often accommodate phenomena like diffraction and polarization after the fact, but Augustin Fresnel's wave optics, with its advanced calculus, let younger scientists generate new predictions, experiments and devices. In his view, a prevailing view is often abandoned not because it can't explain something, but because it doesn't give researchers the opportunity to do new things.

Individuals, Communities and the Limits of Knowledge

On lone geniuses versus collaboration, Buchwald says one to three individuals are usually central when things shift, but they aren't solely responsible. He believes that even without Galileo, someone like Christiaan Huygens, whom he ranks with Newton as one of the two greatest scientists of the 17th century, would eventually have moved things forward, though perhaps differently.

Asked how far along the arc of discovery we are, Buchwald says "I'm not fundamentally a realist": our access to nature is always mediated by what we can do with instruments and materials. He fully respects the standard model's accuracy, but unlike Steven Weinberg he doesn't think we've necessarily reached the depths of reality, and he doubts physics will keep building ever larger accelerators. He notes we still cannot derive chemistry from the standard model, and that the idea that probing nature artificially reveals its natural workings only took hold around the 1500s, among alchemists. He illustrates his view of perception with his classroom examples: a dragonfly would perceive Fridman completely differently, and a PDF on a laptop is not a piece of paper but a construct processed so our perceptual system can interact with it.

Materialism and Consciousness

Buchwald calls himself "a materialist in the deepest sense of the term," believing consciousness arises from particular organizations of material elements. He expects neuroscience, including Caltech's new neuroscience efforts, to reveal more about which brain activity accompanies which experiences, but doubts we can move from brain activity to the experience itself: "Perception is perception." Fridman floats the idea that consciousness could be an undiscovered law of physics permeating all matter, and Buchwald jokes he'd have to stop drinking water if the bottle turned out to be conscious.

Newton's Prism: A Masterclass in Experiment

Buchwald's favorite moment in the history of science is the young Newton's prism experiment. The ancient view held that colors were modifications of white light. Newton, already an excellent mathematician, calculated that at a particular angle a circular beam of sunlight passing through a prism should still form a circle on a distant wall. Instead it formed a long image, suggesting sunlight contains different kinds of light. Prisms were crude, bubble-filled items bought at county fairs.

What fascinates Buchwald is how Newton set the angle: "He held it in his hand" and twiddled it, because at that critical angle the image moves slowest, making it easy to find. This is manipulative experimentation that uses mathematics to overcome built-in measurement problems, something he says no one else was doing then. He notes that until the early 20th century most major experimental breakthroughs came from people who were both strong mathematicians and skilled with their hands. When Newton published, Robert Hooke, author of the influential Micrographia, responded that anything correct in it he already knew, and anything he didn't know was probably wrong.

Perception, Hooke and Hevelius

Buchwald explains a crucial intellectual break visible in Descartes and absorbed by Newton: medieval scholastic thought held that qualities like color exist in the world, while the new view held that colors, sounds and smells are in us. Asking students where the blue in his shirt is, he explains "the blue is actually an artifact of our perceptual system." This skepticism of the senses shaped Newton's later work. Newton even pressed a stick under his eyeball to separate colors produced by the eye from those produced in nature, which Buchwald warns his students not to try.

He tells the story of Johannes Hevelius, a wealthy Danzig brewer who built an observatory on his brewery and claimed extraordinary accuracy for star positions measured with naked-eye sights. Hooke, convinced only instruments could give real knowledge, took Royal Society members into a courtyard to test visual acuity with striped cards and concluded Hevelius's claims were impossible. Yet Edmond Halley, sent to Danzig, found Hevelius really could do it, and modern checks show his numbers were even better than claimed. "Hook was right, but he was also wrong": Hooke essentially measured 20/20 vision for static targets, but Hevelius was watching a bright star move past a pointer, and our eyes, like a frog's, are far more acute at detecting motion.

Newton's Life and the Birth of Calculus

Newton was born in 1642 near Grantham; his father died before his birth, and he resented his stepfather for taking his mother away, leaving him to be raised by his grandmother. As a boy he loved making things, such as kites carrying candles that scared people at night. At Cambridge he began as a subsizar, cleaning up after richer students, and his surviving notebooks show him absorbing the new mechanical philosophy while laying the foundations of calculus. Buchwald says the apple story is not true, quoting colleague Simon Schaffer: "the role of fruit in the history of science has been vastly exaggerated." Instead, Newton's thinking about orbital motion shifted after Hooke suggested, in correspondence, a way of thinking about motion that let Newton bring time into the calculations.

On calculus, Buchwald describes Newton generalizing the binomial theorem and recognizing that calculating areas and tangents are reciprocal operations, with his dot notation still used in physics. Leibniz developed the form we use today, and the priority dispute remains controversial. Buchwald admits he is personally suspicious of Leibniz, citing Domenico Meli's discovery that Leibniz's Tentamen appears to have reverse-engineered results from the Principia, though he notes most historians of mathematics disagree with the stronger claims.

Rivalry, Jealousy and Progress

Buchwald says competition is usually good for science, even if painful for individuals. His favorite example involves François Arago and Jean-Baptiste Biot at the École Polytechnique. Arago, after being captured by pirates during a surveying expedition, returned to find Biot had published their shared work, and later felt Biot muscled in on his research on polarization. Arago then championed the young Augustin Fresnel, giving him space at the observatory, and paper after paper undercut Biot's work, even though Fresnel himself disliked being used in the feud.

Newton had his own temper. As Warden and then Master of the Mint, he pursued counterfeiters and sent at least one, William Chaloner, who had insulted him before Parliament, to the gallows. He was solitary, apparently had no romantic relationships, and was a notoriously poor lecturer; his roommate Humphrey Newton said he might as well have lectured to the walls.

The Plague Years, the Principia, Data and Alchemy

Newton's "miraculous year" of 1666, when he was about 24, produced breakthroughs in calculus and optics, and Buchwald teases his students by asking what they produced during their own pandemic. He doubts going home was essential, though the prism experiments were done there, and an apple tree grown from cuttings still stands outside that window. He describes the three books of the Principia: the laws of motion and forces in geometric form, fluid pressure, and the application to the solar system, where the three-body problem forced approximations, especially for the moon's complex motion.

On data, Buchwald says historians rarely use the phrase scientific method anymore. Before statistical ideas like averaging developed in the mid to late 1700s, scientists like Huygens took many measurements but published only the single one they trusted most, and averaging would have seemed like not knowing what you were doing. He adds that alchemy was far less mystical than assumed: many strange formulas were real recipes for complex amalgams, and Newton spent much of the late 1670s on this work. On religion, Newton was deeply devout but anti-Trinitarian, skeptical of many miracles, and like others of his time believed creation happened about 6,000 years ago.

Newton Meets Einstein

Asked what would happen if Newton met Einstein, Buchwald says Newton's eyes would glaze over if dropped straight into a discussion of spacetime. But take a 40-something Newton, let him ride railroads, touch wires, hear telegraphs and telephones, then tour 1890s laboratories, and his brilliance would let him gradually catch up. The leap from Newton to Einstein, he stresses, involved enormous changes in concepts, mathematics, experimental devices and scientific organization. They close on the mystery of genius, from Einstein's unremarkable brain to savant abilities, and Fridman ends with Kuhn's line: "The answers you get depend on the questions you ask."

Conclusion

Jed Buchwald offers a grounded, human view of science: progress comes less from tidy revolutions than from new tools and techniques that let people do new things, and knowledge is always shaped by our instruments and perception. Newton emerges as both a towering genius and a complicated, solitary, sometimes vindictive man whose brilliance lay in combining mathematics with hands-on manipulation of nature, much of it spent on alchemy and theology as well as physics. Rivalries, flawed measurements and debates over perception all turn out to be part of how science actually moves forward.

This is a summary of "#214 – Jed Buchwald: Isaac Newton and the Philosophy of Science" from Lex Fridman Podcast, giving you the GIST so you can decide if you want the REST. Listen to the full episode.