Subtitles section Play video
-
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 simply “not 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 method—in 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 abstractions—rules,
-
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 Alexander “the Great” reminds 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, kill “barbarians,” 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, meaning “walkie” and thus informal—not
-
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 Soul—which is actually an amazing book
-
of proto-biology-meets-psychology—and his school's highly influential set of textbooks
-
on natural philosophy, called Physics.
-
How did Aristotle answer our big questions
-
about physics, such as “what was stuff?”
-
And “where 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 geometric “platonic 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 stars—that is, the planets—followed
-
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 weird… but it does go up, I guess?
-
And way out beyond these four terrestrial spheres—out past the Moon—spun 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 experience… and 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 color—which is awesome—and
-
that male octopi have a special arm called a “hectocotylus”—which is… something
-
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 question “what 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 humans—and only humans—have 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 not “humans,” but dudes: according to him, cold maternal blood produced inferior
-
humans, AKA girls, while hot paternal semen produced boys.
-
Aristotle was… maybe 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 Being—that 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 cosmos—even if wrong in their
-
particulars—inspired 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 time—we'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.