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  • Pop quiz: are you a Platonist or an Aristotelian?

  • An idealist or an empiricist?

  • Do you think up neat rules to describe the universe and then try to fit data into your theory?

  • Or do you observe the world and draw conclusions from what you see?

  • Do you trust math, or your senses?

  • Before you decide, let's take a trip to urban Athens circa 399 BCE

  • [Intro Music]

  • Last week, we met the Presocratics: despite

  • having by any reasonable standard invented science in Europe, these thinkers are lumped

  • together today as simplynot Socrates.”

  • So who was this smarty pants?

  • Socrates didn't have a single, clearly formulated natural philosophy.

  • He didn't even study nature!

  • He studied politics and morality and prided himself on not claiming to know things.

  • But Socrates did two important things: he asked a lot of questions, which influenced

  • how philosophers went about teaching their ideas.

  • And he inspired the two rockstars of classical Greek philosophy.

  • Socrates held that knowledge comes from asking questions.

  • So many questions!

  • His name is attached to the Socratic methodin which you constantly ask questions so that

  • students can steadily break down a big problem into smaller parts, parts they can test hypotheses against.

  • It's okay if they realize that a hypothesis is wrong: in fact, it's good!

  • It means they're moving away from falsehood.

  • The Socratic method is an example of negative hypothesis elimination, or proving that something

  • is wrong to narrow down the possibilities of what might be right.

  • But Socrates's biggest legacy might be his student, Plato, and his student's student,

  • Aristotle.

  • Both were inspired by Socrates's methods, but they arrived at some very different conclusions

  • about the world.

  • We know a lot about Socrates thanks to his

  • students.

  • Chiefly Plato founded a physical school called the Academy to train Athenians in how to think

  • like Socrates.

  • Plato wrote down dialogues between Socrates and other thinkers including Parmenides: he

  • was the Eleatic philosopher who believed that nothing really changes, and thus we can't

  • trust our senses.

  • This had a big impact on Plato.

  • Whose best known works include Republic, in which Socrates defines justice and argues

  • for rule by philosopher-king instead of democracy, and Timaeus, in which Socrates talks

  • about the nature of the universe.

  • Plato had a big impact on thinking about thinking.

  • Today, we still use Plato's name for a place of philosophical learning, “Academy,”

  • to describe the concept of higher education in general.

  • At the original Academy, Plato emphasized training in how to think properly.

  • Over the door of the Academy was inscribed the dictum, “Let no one enter here who is

  • ignorant of geometry.”

  • Plato based his own philosophy on geometrical laws.

  • He taught a Pythagoras-inspired idealism, or a theory of nature based on perfect abstractionsrules,

  • of which real-world stuff could only ever be imperfect examples.

  • So Plato had to fit his observations to his theory.

  • That idealism is one of the reasons people think of Plato as more of a philosopher than

  • a scientist.

  • Plato built on the work of the Presocratic schools.

  • But he developed a more complete way of looking at the natural world than they did.

  • And his students took off in search of solutions, even as they changed his underlying theory.

  • The only Greek who wrote more philosophy than Plato was Plato's own star student and rival,

  • Aristotle.

  • Compared to Plato's idealistic abstractions,

  • Aristotle's philosophy makes more common sense.

  • His ideas are based on empirical evidence: he observed the world and then came up with

  • a theory that explained it.

  • This order of operations is at the heart of modern scientific practices.

  • Aristotle was from Macedonia, in the north of Greece.

  • But he studied at Plato's Academy in Athens for twenty years, until Plato died.

  • Afterward, Aristotle took a lucrative gig: King Philip II of Macedonia hired him as tutor

  • to his son, Alexander.

  • And, you know this particular Alexander: he decided to conquer the entire earth.

  • Before age thirty, he ruthlessly conquered much of Asia, Africa, and Europe, ruling over

  • more area than anybody until Genghis Khan.

  • Aristotle's influence on Alexanderthe Greatreminds us that science is

  • always social.

  • From the very beginning, scientists have served bad, heartless dudes.

  • Aristotle, a man who literally wrote the book Ethics, pushed his most famous pupil to invade

  • Persia, killbarbarians,” and become a brutal warlord.

  • After Alexander died young, Aristotle went back to Athens to start his own school, the

  • Lyceum.

  • The Lyceum was pretty different from Plato's Academy.

  • Because Aristotle liked plants and liked to walk and talk, his school wasn't in a building,

  • but a grove of trees outside the city.

  • And his school was called the Peripatetic, meaningwalkieand thus informalnot

  • like the Academy.

  • It was during the Lyceum years that Aristotle probably wrote many of his most famous works,

  • including Metaphysics, On the Heavens, On the Soulwhich is actually an amazing book

  • of proto-biology-meets-psychologyand his school's highly influential set of textbooks

  • on natural philosophy, called Physics.

  • How did Aristotle answer our big questions

  • about physics, such aswhat was stuff?”

  • Andwhere are we?”

  • He posited a complete system, joining the elements and the heavens.

  • This became the basis for European thought about the physical world for two thousand years!

  • Let's compare Aristotle's system to his mentor Plato's in this week's ThoughtBubble.

  • For Plato, the cosmos was perfect.

  • It had perfect rules that could be studied.

  • And all cosmic stuff was made up of atoms that were perfect geometricplatonic solids”,

  • each creating one element: tetrahedrons of fire, cubes of earth, octahedrons of air,

  • icosahedrons of water, and dodecahedrons as the shape of the whole universe

  • Like a giant celestial set of D&D dice!

  • Plato's theory of the heavens stated that the wandering starsthat is, the planetsfollowed

  • a path of uniform circular motion.

  • You see,

  • the wandering stars must move in perfect circles, since the cosmos is orderly.

  • Ah, but this one is moving backwards!

  • Plato's students could see that Mars, for one, seemed to jump backwards, showing retrograde

  • motion.

  • Plato didn't really have an explanation.

  • European astronomers would spend the next two thousand years meticulously trying to

  • solve this problem.

  • They'd end up learning a lot in the process.

  • How did Aristotle build on Plato's system? Aristotle's cosmology was abstract, too,

  • but attempted to make sense of observations about the world.

  • He crossed those same four elements, plus a new anti-void one called æther, with four

  • physical sensations: hot and cold, dry and wet, and used these to explain everything:

  • Earth was the heaviest element, so it was the center of the cosmos.

  • Water was lighter than earth so the oceans rested on top of the earth.

  • So far so good.

  • Air's natural state is above water.

  • That also checks out!

  • Fire sat on top of air, which is a little weirdbut it does go up, I guess?

  • And way out beyond these four terrestrial spheresout past the Moonspun the stars,

  • acting according to their nature as ætherial, or perfect-circle-moving, objects.

  • And nowhere, anywhere in this theory, was a void.

  • Nature abhors a vacuum!

  • In Aristotle's cosmos, all of the elements were actively trying to get back to their

  • natural states.

  • Why did flames rise?

  • They were just trying to get back to the fiery celestial realm above the air.

  • Thanks Thought Bubble.

  • From the Presocratics to Plato to Aristotle, we've ended up with a bunch of spheres inside

  • of spheres, each with a natural tendency.

  • This confirmed the average Bronze Age farmer's experienceand ours.

  • The earth seems to stand still.

  • Water sits on earth.

  • Air isn't very heavy.

  • Aristotle recognized that elements didn't always exist in their pure forms.

  • A tree, for example, was a combination of earth, water, and air: roots go down into

  • the earth, and branches up into the air.

  • His theory also worked for comparisons.

  • Why does a book fall faster than a piece of paper?

  • Because it has more earth in it.

  • Aristotle could even explain natural phenomenon.

  • Why does rain fall from the sky to the ground?

  • Why do volcanoes shoot fire up?

  • Obviously this isn't how I think gravity works, but it's a way of explaining it that

  • made sense to the Ancient Greeks.

  • Where Plato saw a world of ideal shapes, Aristotle had a theory that acknowledged that we're

  • all kind of a hot mess.

  • Things are naturally jumbled up, but always trying to get back to their essential place.

  • [Living things] Aristotle also loved looking at living things.

  • And he looked closely.

  • He noticed, for example, that the octopus can change colorwhich is awesomeand

  • that male octopi have a special arm called a “hectocotylus”—which issomething

  • you should Google.

  • Because it's weird and gross but also kind of awesome.

  • And it wasn't confirmed by scientists until the 1800s!

  • Aristotle thus trusted that knowledge proceeded from the experience of the senses.

  • In works such as History of Animals, among others, he wrote down observations like these

  • about all kinds of organisms.

  • He also tried to classify the world in an orderly system, giving rise to taxonomy.

  • When he attempted to answer the questionwhat is life,” the taxonomy he created relied

  • on a system of souls.

  • Plants have a vegetative soul, responsible for reproduction and growth.

  • Animals have a vegetative and a sensitive or animal soul, responsible for mobility and

  • sensation.

  • And humansand only humanshave a vegetative, a sensitive, and a rational soul, capable

  • of thought and reflection.

  • This led Aristotle to further theorize that all things can be placed on a line from simplest-slash-least-soulful

  • to highest-slash-most-soulful.

  • On one end, he placed plants, then worms, and so on.

  • These low animals bore their offspring cold, dry, and in thick eggs.

  • The higher animals made warm and wet babies.

  • So of course, at the other end of the line, Aristotle placed men.

  • Meaning nothumans,” but dudes: according to him, cold maternal blood produced inferior

  • humans, AKA girls, while hot paternal semen produced boys.

  • Aristotle wasmaybe not someone we'd want to elect as our philosopher-king today?

  • But Aristotle's system of classification again seemed to confirm his classical and

  • medieval readers' daily experiences.

  • His proto-biological ideas stuck around in various forms until Darwin, getting lumped

  • under the heading of the Great Chain of Beingthat all creatures on earth stand somewhere on

  • a ladder of perfection up toward God.

  • You may have already guessed that this concept has been particularly troublesome when it

  • comes to scientific racism.

  • But that's a story for later.

  • The creepier effects of some his ideas aside,

  • Aristotle had an answer for everything.

  • For the most part, these were based in observation and conformed to common sense.

  • His answers were able to explain how the world worked

  • most of the time.

  • And not only did Aristotle come up with a complete theory of everything, he wrote it

  • down.

  • He was a prolific author, and a significant percentage of his texts have survived thanks

  • to our Arabian scholars.

  • Then again, Plato's transcendental ideas about the cosmoseven if wrong in their

  • particularsinspired centuries of scholars to think about the universe as having underlying

  • laws, ones that hold regardless of what our senses can show us.

  • So are you a Platonist or an Aristotelian?

  • Or, taking a page from Socrates, is that a trick question!?

  • Next timewe'll follow Alexander the Maybe-Not-So-Great to India to witness the rise of the Maurya

  • dynasty, set the earth spinning on its axis, and found a science of life!

  • Crash Course History of Science is filmed in the Dr. Cheryl C. Kinney studio in Missoula,

  • Montana and it's made with the help of all this nice people and our animation team is

  • Thought Cafe.

  • Crash Course is a Complexly production.

  • If you wanna keep imagining the world complexly with us, you can check out some of our other

  • channels like Scishow, Nature League, and The Financial Diet.

  • And, if you'd like to keep Crash Course free for everybody, forever, you can support

  • the series at Patreon; a crowdfunding platform that allows you to support the content you

  • love.

  • Thank you to all of our patrons for making Crash Course possible with their continued

  • support.

Pop quiz: are you a Platonist or an Aristotelian?

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Plato and Aristotle: Crash Course History of Science #3

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    林俞均 posted on 2018/11/30
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