Okay, picture this. It's around 585 BCE. Two armies, the Lydians and the Medes, are locked
in a brutal battle. Swords clashing, blood everywhere, the whole nine yards. And then, the sun starts
to disappear. Now if you're a soldier in 585 BCE, you know exactly what this means, right?
The gods are pissed. This is divine intervention. This is the universe itself telling you to
stop fighting. Both armies drop their weapons. The battle ends. A peace treaty gets signed
on the spot. But here's what's remarkable, and this is where our story really begins. There
was one guy who saw this coming. Not because he had divine visions. Not because he consulted
oracles or read animal entrails. But because he'd been paying attention to patterns. He'd
been doing math. His name was Thales, and he just changed everything. See, what Thales did
that day wasn't just predict an eclipse. though that alone would be pretty damn impressive
for 585 BCE. What he did was introduce a radical idea, that the universe operates according
to natural laws that human beings can understand through observation and reason, not mythology,
not divine whim, not because Zeus said so. Natural laws. This might not sound revolutionary to
you. You grew up with science, with the scientific method. with the assumption that the universe
makes sense and we can figure it out. But in Thales' time, this was heresy. This was dangerous.
This was the beginning of everything we now call philosophy, science, and rational thought.
Throughout this lecture, we're going to explore how one man from a prosperous trading city
in Ionia fundamentally altered the course of human intellectual history. We'll look at his
contributions to mathematics, his theories about the nature of reality and why, 2600 years later,
we're still talking about a guy who thought everything was made of water. Yes, water. We'll
get to that. Trust me, it's weirder and more brilliant than it sounds. So who was this Thales
character? Well, let me tell you. He wasn't some ascetic monk living in a cave contemplating
the cosmos. Thales was basically the ancient Greek version of a successful businessman who
got really, really into side projects. He was born around 624 BCE in Miletus. And here's
what you need to know about Miletus. was basically the Silicon Valley of the ancient world. Prosperous
trading hub. Cultural crossroads. Ideas flowing in from Egypt, Babylon, Phoenicia. If you wanted
to be where things were happening in the 6th century BCE, Miletus was the place. Thales
came from money. His family was probably involved in trade, which meant he had two things most
ancient Greeks didn't have. Resources and exposure to different cultures. He traveled extensively.
Egypt. Babylon, probably other places we don't even know about. He soaked up mathematical
knowledge from the Egyptians, astronomical observations from the Babylonians. But here's what makes
Thales different from just another well-traveled rich guy. He didn't just collect knowledge
like souvenirs. He questioned it. He tested it. He tried to find the underlying principles.
The Egyptians could calculate the area of a triangle? Great. But why does that method work?
What's the principle behind it? The Babylonians could track celestial movements? Fantastic.
But what causes those movements? What's really going on up there? This insatiable curiosity,
this refusal to accept, that's just how it is, as an answer. This is what makes Thales the
father of Western philosophy. Not because he had all the answers. He definitely didn't.
The guy thought everything was made of water for crying out loud. But he asked the right
questions. and he insisted that those questions could be answered through human reason rather
than divine revelation. Now Thales wasn't just an ivory tower intellectual. He was involved
in politics, he was involved in commerce. According to one story, probably apocryphal but I love
it anyway, his fellow citizens used to mock him for being so impractical, always lost in
thought about abstract concepts. So one year, Thales used his astronomical knowledge to predict
that the olive harvest would be exceptional. He quietly bought up all the olive presses
in the region when they were cheap. Harvest time comes, olives everywhere, and suddenly
everyone needs to rent Thales' olive presses. He made a fortune. The point wasn't the money.
He was already wealthy. The point was proving that philosophers aren't impractical dreamers.
We can engage with the real world when we want to. We just usually have more interesting things
to think about than olive presses. But let's get to what Thales is really remembered for.
Let's talk about the mathematics that change geometry forever. Alright, so we've established
that Thales was this curious, well-traveled businessman-philosopher who refused to accept
traditional explanations. Now let's talk about what he actually did with all that curiosity.
Because here's the thing about Thales. He didn't just observe the world and make clever guesses.
He created proofs. He took mathematical knowledge that had been floating around the ancient world,
practical tricks the Egyptians used for surveying land, techniques the Babylonians used for astronomy,
and he asked a question nobody had really asked before. But can we prove this is always true?
This is huge. This is the birth of mathematical proof as we know it. Before Thales, mathematics
was basically a collection of useful recipes. If you want to find the area of this field,
do these steps. If you want to calculate when the Nile will flood, use this method. It worked,
but nobody really knew why it worked. It was like having a cookbook without understanding
chemistry. Thales said, No, we need to understand the underlying principles. We need to demonstrate
why these things are true, and this is where it gets beautiful. Look at what's on this slide.
Three major contributions. First, Thales' Theorem. The theorem that still bears his name 2,600
years later. The idea that any triangle inscribed in a semicircle, where one side is the diameter,
will always have a right angle. Not sometimes, not usually. Always. Think about that. Thales
looked at circles and triangles and discovered an eternal truth. A relationship that was true
before humans existed, and will be true after we're gone. That's not just mathematics, that's
touching something fundamental about reality itself. Now, I know what some of you are thinking.
Great, Professor Leshly, another dead Greek guy and his triangles. When am I ever going
to use this? Fair question. But here's the thing. You already are using it. Every time you use
GPS, every time a building doesn't fall down, every time an engineer designs literally anything,
They're building on the foundation Thales laid. The idea that we can discover universal truths
through logical reasoning? That's Thales. But let's look at his other contributions on this
slide. Second, he established the relationship between an object's size and its distance from
an observer. This is the foundation of trigonometry, of surveying, of navigation. Thales figured
out that you can use proportions and similar triangles to measure things you can't directly
reach. Which brings us to third, His methods for calculating the height of pyramids and
the distance of ships at sea. Now we're going to dig into that pyramid story in detail in
a moment, because it's both brilliant and possibly complete nonsense. Historians still argue about
whether it actually happened. But the method? The method is genius. What Thales understood,
and this is the key insight, is that mathematics isn't just about counting things. It's about
finding relationships, patterns, proportions. Universal principles that apply everywhere.
He took practical problems and transformed them into theoretical knowledge. And then, and this
is crucial, he took that theoretical knowledge and applied it back to practical problems.
This is the birth of applied mathematics. This is the moment when human beings realized we
could use abstract reasoning to solve concrete problems. Okay, let's get into the weeds a
bit with Thales' theorem because this is where we see his genius most clearly. The theorem
states If you have points A, B, and C on a circle, and AC is the diameter of that circle, then
angle ABC, the angle at point B, is always a right angle. Always. Every single time. Now
why is this true, and more importantly, how did Thales prove it? Here's what's remarkable.
Thales used the properties of isosceles triangles. He understood that if you draw lines from
the center of the circle to points B and C, you create two isosceles triangles. And because
the angles in any triangle sum to 180 degrees, and because of the special properties of these
isosceles triangles, the angle at B must be 90 degrees. It's elegant. It's beautiful. It's
the kind of proof that makes you go, oh, of course that's true once you see it. But here's
what really matters. This wasn't just an interesting geometric curiosity. This theorem became absolutely
foundational to Euclidean geometry. When Euclid wrote his elements a few centuries later, basically
the most influential mathematics textbook in human history, Thales' insights were baked
right into the foundation. You know, I remember the first time I really understood this theorem.
Not just memorized it for a test, but actually got it. I was probably about your age, sitting
in a geometry class, half asleep, and suddenly it just clicked. The relationship between the
circle and the triangle, the inevitability of that right angle. I literally sat up straight
in my chair. The teacher thought I was having a medical emergency. But that's what good mathematics
does. It wakes you up. It shows you that the universe has structure, has order, has these
beautiful eternal relationships that we can discover and understand. Now, let's talk about
applications, because this isn't just abstract beauty, though the beauty matters. Thales'
theorem gives us a way to construct perfect right angles using nothing but a circle and
a straight edge. Think about what that means for ancient builders. For architects. for anyone
who needs to create perpendicular lines, which is basically everyone who builds anything.
You don't need fancy tools. You don't need divine inspiration. You just need to understand the
relationship between circles and triangles, and you can create perfect right angles every
single time. And this is what Thales was really doing. He was showing that the universe operates
according to rational principles that humans can discover and use. Not magic, not divine
favor. not secret knowledge passed down from the gods. Just observation, reason, and logical
proof. Every time you use a carpenter's square, every time you see a building with perfect
right angles, every time you encounter anything that relies on geometric precision, you're
seeing Thales's legacy. You're seeing the power of human reason to unlock the secrets of reality.
Of course, Thales didn't stop there. Because apparently proving fundamental theorems of
geometry wasn't enough to keep him busy. No, he also decided to measure the Great Pyramid
of Giza using shadows. And that story, which may or may not be true but is definitely awesome,
that's what we're going to look at next. Because it shows Thales at his most clever, his most
practical, and his most, I'm going to solve this problem using nothing but basic geometry
and sheer audacity. So let's talk about pyramids, shadows, and why historians still argue about
whether this actually happened. Alright, so imagine you're standing in front of the Great
Pyramid of Giza. It's already ancient when Thales sees it, built over 2,000 years before his
time. This thing is massive. We're talking 481 feet tall originally, covering 13 acres at
the base. It's one of the most impressive structures human beings have ever built. And some Egyptian
guide, probably used to impressing tourists, says to Thales, Pretty amazing, right? Nobody
knows exactly how tall it is. and Thales, being Thales, apparently said, Hold my wine. I'll
figure it out. Now I want you to appreciate the sheer audacity of this moment. You can't
exactly climb to the top with a measuring tape. You can't see the top and the base at the same
time to triangulate. The Egyptians who built it didn't leave the blueprints lying around,
but Thales had something better than blueprints. He had geometry and he had shadows. Here's
how the story goes and I want to emphasize this is legend. We're not 100 % certain this actually
happened, but the method is absolutely sound. Thales waited for a specific time of day, the
moment when the length of his own shadow equaled his height. You know this moment. It happens
twice a day, when the sun is at a particular angle, around 45 degrees above the horizon.
At that exact moment, he measured the pyramid's shadow. And because of the proportional relationship
he'd discovered, because at that angle, height equals shadow length, For any object, the pyramid's
shadow gave him the pyramid's height. Well, almost. He had to add half the length of the
pyramid's base, because the shadow extends from the center point, not the edge. Do you see
what he did here? He took an impossible problem, measuring something impossibly tall, and transformed
it into a simple problem. He used the relationship between similar triangles, the predictable
movement of the sun, and basic proportional reasoning. No fancy equipment. No divine revelation.
Just observation, patience, and mathematical insight. This is applied geometry at its finest.
This is the human mind looking at reality and saying, I can figure this out. I can measure
the unmeasurable. Now here's where it gets fun. Modern historians love to argue about this
story. Some say it definitely happened. We have multiple ancient sources mentioning it. Others
say it's too good to be true, probably embellished over time. One historian pointed out that Thales
would have needed to account for the pyramid's slope, the irregular shape of the shadow, atmospheric
refraction. To which I say maybe he did. Or maybe he got close enough that the Egyptians
were impressed and that's what mattered. The story doesn't claim he calculated it to the
millimeter. It claims he figured out a clever method to get a reasonable measurement. But
here's what really matters. Whether or not this specific story is true, We know Thales developed
methods for using proportions and similar triangles to measure distant objects. We know he understood
the relationship between an object's height and its shadow. We know he applied geometric
principles to practical problems. The pyramid story is memorable because it's dramatic. But
the real achievement is the method, the insight that you can use mathematics to solve problems
that seem impossible. And speaking of seemingly impossible achievements, let's talk about that
solar eclipse. Okay. We need to talk about what might be the most famous thing Thales ever
did. The solar eclipse of 585 BCE, the one that stopped a war. Now, I started this lecture
with this story because it's dramatic and it hooks your attention. But now let's dig into
what actually happened, or what we think happened, and why it matters. According to the ancient
historian Herodotus, Thales predicted that a solar eclipse would occur in a particular year.
And it did. On May 28th, 585 BCE, The sun went dark right in the middle of a battle between
the Lydians and the Medes. Both armies interpreted this as a sign from the gods. They stopped
fighting. They negotiated peace. The eclipse literally ended a war. But here's what's absolutely
remarkable about this. If Thales actually predicted this eclipse, and that's a big if we'll get
to in a moment, then he was using astronomical knowledge to forecast a celestial event. Think
about what that means. He was saying, The universe operates according to patterns, predictable
patterns, patterns we can understand and use to know what will happen in the future. This
isn't prophecy. This isn't divine revelation. This is science. This is the scientific method
in embryonic form. Observe patterns, develop a theory, make predictions, test those predictions
against reality. Now here's where modern scholars get all worked up and start throwing shade
at poor Thales. Well actually, Professor Leshly, the Babylonians had eclipse cycles, but they
could only predict lunar eclipses with any accuracy. Solar eclipses are much harder because you
need to know the exact location where the eclipse will be visible. The mathematics required to
predict a solar eclipse visible from a specific location in Asia Minor wouldn't be developed
for centuries. Okay, fair points. The skeptics might be right. Maybe Herodotus got the story
wrong? Maybe Thales predicted an eclipse but not the eclipse. Maybe he got lucky. Maybe
the whole thing is apocryphal. But here's what we do know for certain. First, there was a
solar eclipse on May 28th, 585 BCE, visible from Asia Minor. Modern astronomy confirms
this, so the eclipse part of the story is definitely true. Second, Thales had access to Babylonian
astronomical records. He traveled. He studied. He knew about eclipse cycles, the Sorrow Cycle,
which repeats every 18 years and 11 days. Third, even if he couldn't predict the exact time
and place with modern precision, he could have made an educated guess that an eclipse was
likely in a particular year or season. And here's what really matters. Whether the prediction
was precise or approximate, whether it was skill or luck, the story tells us something crucial
about how Thales was perceived. His contemporaries believed he could predict celestial events
using natural knowledge. They believed he understood patterns in the cosmos. They believed human
reason could unlock the secrets of the heavens. That belief, that conviction that the universe
is knowable, that it operates according to natural laws we can discover, that is Thales's real
legacy. Not the specific eclipse prediction, but the entire worldview it represents. This
is the birth of the scientific worldview. The idea that 1. The universe operates according
to natural laws 2. These laws are consistent and predictable 3. Human beings can discover
these laws through observation and reason 4. We can use this knowledge to make predictions
about the future. Every scientific achievement since Thales, every discovery, every technological
advancement, every time we've used knowledge to improve human life, rests on these foundational
assumptions. You know, I sometimes wonder what Thales would think if he could see us now.
We can predict eclipses centuries in advance down to the second. We've sent robots to Mars.
We've photographed black holes. Would he be surprised? Or would he just nod and say, yeah,
that's what happens when you pay attention to patterns and use your brain. Took you long
enough. I like to think it would be the latter. But we've been talking about Thales the mathematician,
Thales the astronomer. Thales the Practical Problem Solver. Now it's time to talk about
Thales the Philosopher. Because his most influential idea, the one that really launched Western
philosophy, wasn't about triangles or eclipses or pyramids. It was about water. Yeah. Water.
Everything is water, according to Thales. And before you laugh, and trust me, your first
instinct is to laugh. Let me explain why this seemingly ridiculous idea is actually one of
the most important philosophical insights in human history. Alright, so, water. Everything
is water. I can see some of you looking at your desks right now, tapping on the wood, thinking,
Professor Leshley, I'm pretty sure this desk is not water. I'm pretty sure I'm not water.
I'm pretty sure Thales lost his mind somewhere between measuring pyramids and making wild
claims about the fundamental nature of reality. And look, I get it. On the surface, pun intended,
this sounds absolutely bonkers. But stay with me here, because what Thales was actually doing
is so much more sophisticated than it first appears. Here's what Thales was really asking.
What is the fundamental substance of the universe? What is the one thing that everything else
comes from? Now why is this question revolutionary? Because before Thales, the answer would have
been, the gods made everything. Zeus did this, Poseidon did that. Different gods made different
things for different reasons. Thales said, No. I think there is one underlying substance,
one fundamental material that takes different forms to create everything we see. This is
monism, the idea that reality is fundamentally unified, that beneath all the apparent diversity,
rocks, trees, animals, humans, stars, there's a single common substance, and this changes
everything. Because if everything comes from one substance, then the universe isn't a chaotic
mess of competing divine wills. It's a unified system. It operates according to consistent
principles. It can be understood. So why water specifically? Well, Thales wasn't just pulling
this out of thin air, or out of water, I suppose. He had reasons. Look at what he observed. First,
all life depends on water. Plants need it. Animals need it. Humans need it. No water,
no life. That's a pretty fundamental role right there. Second, water exists in multiple states.
It's liquid in rivers and oceans. It's solid as ice. It's vapor in clouds and steam. Here's
a single substance that can transform itself into radically different forms. Think about
what that means. Thales is looking at water and seeing a model for how one substance could
become many things. Ice doesn't look like steam, but they're both water. Maybe... Just maybe.
Everything that looks different is actually the same fundamental substance in different
forms. Third, land seems to emerge from water. Islands rise from the sea. The Nile floods
and deposits fertile soil. Thales lived in a coastal city. He saw how water and earth interact
constantly. Now, was Thales right? Obviously not, in the literal sense. We know now that
matter is made of atoms, that there are over 100 elements. that water itself is a compound
of hydrogen and oxygen. But here's what Thales got right. He understood that there's an underlying
unity to nature, that what appears diverse might share common principles. That transformation
is possible, that substances can change form while maintaining some essential identity.
Modern chemistry, modern physics, they're still asking Thales's question. What is everything
made of? We've just gotten more sophisticated answers. Atoms, subatomic particles, quantum
fields, maybe strings. But the question, that's pure Thales. And here's the really crucial
part. Thales was proposing a natural explanation. Not the gods did it, not it's a mystery beyond
human understanding, but there's a natural substance that behaves according to natural principles.
This is the birth of natural philosophy. the ancestor of what we now call science. Look
at this phrase on the slide, a monistic view. This is one of the fundamental questions in
philosophy. Is reality fundamentally one thing or many things? Is the universe unified or
fragmented? Thales came down firmly on the side of unity. And that choice, that commitment
to finding underlying patterns and common principles, that's what makes science possible. Now, I
know what you're thinking. Okay, professor. I get that the question was important. But
seriously? Water? He couldn't have picked something a little less... wet? Fair enough. His student
Anaximander thought Thales was too specific. He proposed something called the apiron. The
infinite, undefined, boundless something or other that everything comes from. Another student,
Anaximenes, said, No, no. It's obviously A.I.R. Everything is air. So there was definitely
some disagreement in the Milesian school about what the primal substance actually was, but
here's what they all agreed on. There is a primal substance. The universe is fundamentally unified.
Nature operates according to natural principles that human reason can discover. That consensus
that shared commitment to rational inquiry into nature, that's what launched Western philosophy
and science. Okay, so Thales thinks everything is water. That's weird enough. But then he
makes another claim that sounds even stranger to modern ears. Now before you write him
off as completely out there, let's talk about what he actually observed and what he was trying
to explain. Thales was the first Greek philosopher we know of to study magnets systematically.
He observed that lodestone, A naturally magnetic iron ore could attract iron. It could make
iron move without touching it. Think about how weird that is if you've never encountered the
concept of magnetism before. Here's a rock that can make other objects move from a distance.
No visible connection, no obvious mechanism, just... action at a distance. How do you explain
that? In Thales' worldview, where everything operates according to natural principles, How
do you account for a rock that seems to have the power to move things? His answer? The magnet
has a soul. It has some kind of animating force, some vital principle that gives it the power
to act. Now, I can hear the objections already. Professor Leshley, that's not a soul, that's
a magnetic field. We understand magnetism now, it's one of the fundamental forces of nature.
Yes, exactly. It is one of the fundamental forces of nature. But Thales didn't have the concept
of fundamental forces. He didn't have field theory. He didn't have Maxwell's equations.
What he had was the observation that some objects have the power to affect other objects without
direct contact. And his explanation, crude as it sounds to us, was an attempt to account
for that power using the conceptual tools available to him. So what did Thales mean by soul? Not
what we mean today. Not consciousness, not personality. not the thing that goes to heaven or gets reincarnated.
For Thales, soul meant something more like animating principle, or power of motion or vital force.
Look at this phrase, the soul is a force that permeates all things. Thales believed that
there was some kind of vital energy running through the entire universe, that everything,
not just obviously living things, participated in this cosmic aliveness. This is called High
Lozohism. The idea that matter itself is alive, that there's no sharp distinction between living
and nonliving things. Now, is this true? Well, no, not in the way Thales thought. We don't
think rocks are alive. We don't think magnets have souls. But here's what's fascinating.
Thales was grappling with a real problem. How do we explain causation? How do we explain
why things happen? What gives objects the power to affect other objects? Modern physics is
still asking these questions. What is a force? What is energy? How does causation actually
work at the quantum level? We have better answers than Thales, but we're asking his questions.
And here's something else to consider. Thales' view of the soul had profound implications
for how he saw the universe. If everything has soul, if everything participates in this vital
force, then the universe is fundamentally alive. It's not dead matter being pushed around by
external forces. It's a living, dynamic, interconnected system. This connects directly to his idea
about water as the primal substance. Water flows, water moves, water seems alive. Maybe that's
part of why he chose it, because it embodies this principle of vitality, of constant motion
and transformation. Now, Thales' ideas about the soul influenced later philosophers in ways
that are kind of hilarious if you know the history. Plato took the idea of soul and ran with it
in a completely different direction. The soul is the immortal, rational part of humans that
exists before birth and after death. Aristotle wrote an entire treatise called On the Soul,
where he systematically disagrees with almost everything his predecessors said about it.
So Thales started a conversation that philosophers are still having 2600 years later, not bad
for a guy who thought magnets were alive. But here's the deeper point. Thales was trying
to create a unified theory of reality. Everything is water. Everything has soul. Everything is
connected. Everything operates according to natural principles. He was looking for the
underlying unity beneath apparent diversity. He was trying to explain how the universe works
without appealing to mythology or divine intervention. And this, this commitment to natural explanation,
this search for underlying unity, this conviction that human reason can understand reality, this
is what makes Thales the father of Western philosophy. Not because he got everything right. He didn't.
But because he asked the right questions. Because he insisted on natural explanations. Because
he believed the universe made sense and we could figure it out. Look at that last bullet point.
Influence on later philosophers. Plato, Aristotle, the Stoics, medieval philosophers, modern philosophers.
They're all responding to questions Thales first raised. What is the fundamental nature of reality?
How do we explain change in motion? What is the relationship between unity and diversity?
What is the soul? These aren't just historical curiosities. These are live philosophical questions.
We're still working on them, so we've seen Thales the mathematician, Thales the astronomer, Thales
the natural philosopher with his water and his souls and his magnets. Now let's zoom out and
look at his broader impact. Because Thales didn't just have interesting ideas, he started a whole
tradition. He founded a school. He inspired students who went on to develop their own philosophical
systems. Let's talk about the Milesian School and how Thales' legacy shaped the entire trajectory
of Western thought. Alright, so here's what happens when you're the first person to say,
maybe we should explain the universe using reason instead of mythology. You start a movement.
Thales didn't just have interesting ideas and then disappear into history. He taught students.
He inspired followers. He created what we now call the Milesian School. the first philosophical
school in Western history. And his students? They didn't just memorize his teachings and
repeat them. They argued with him. They developed their own theories. They pushed his ideas in
new directions. This is what real intellectual tradition looks like. Not blind acceptance,
but creative disagreement. Not the master said it so it must be true, but the master said
it, and here's why I think he was wrong. Let's look at two of Thales's most important students.
Anaximander and Anaximenes. First, Anaximander. Now, Anaximander looked at his teacher's theory,
everything is water, and said, I appreciate what you're trying to do here, Thales, but
I think you're being too specific. Why water? Why not fire? Why not air? Why not earth? If
you pick any particular substance as the fundamental stuff of reality, you're going to have trouble
explaining how it becomes all the other substances. So Anaximander proposed something brilliantly
abstract, the apyron, the boundless, the infinite, the undefined. Think about how sophisticated
this is. Anaximander is saying, the fundamental reality can't be any specific thing we observe
in nature. It has to be something more basic, more primordial, something that contains the
potential for all specific things, but isn't itself any particular thing. This is a huge
conceptual leap. This is moving from concrete observation to abstract theorizing. This is
philosophy getting more philosophical. And Anaximander didn't stop there. He developed the first known
map of the world. He proposed that the Earth floats freely in space, unsupported, which
was a radical idea when everyone assumed it had to be resting on something. He developed
an early theory of evolution, suggesting that humans evolved from fish. The guy was a genius.
And he got there by taking Thales' approach. natural explanation, rational inquiry, and
pushing it further. Now the other student, Anaximenes, looked at both Thales and Anaximander and basically
said, you're both overthinking this. Thales says water. Anaximander says the infinite,
undefined, boundless whatever. Anaximenes says it's air. Obviously it's air. Look, air can
become denser and turn into water than ice. Air can become rarer and turn into fire. Air
is everywhere. Air is what we breathe. It's literally the stuff of life. Case closed. Now,
you might think this is a step backward, going from Anaximander's sophisticated abstraction
back to a concrete substance, but actually Anaximenes was doing something clever. He was trying to
explain the mechanism of transformation. See, Thales said everything is water, but he didn't
really explain how water becomes other things. Anaximander said everything comes from the
Epiron, but that's so abstract it's hard to work with. Anaximenes said Air transforms through
rarefaction and condensation. It gets thinner or thicker. And this gives you a mechanical
explanation for how one substance becomes many different things. This is important. This is
the beginning of trying to explain not just what things are made of, but how transformation
actually works. But here's what I want you to notice. All three of these philosophers, Thales,
Anaximander, Anaximenes, they're all asking the same fundamental question. What is the
underlying unity of reality? They disagree about the answer. Water, apirin, air. But they agree
about the question. They agree that there is an underlying unity. They agree that it can
be discovered through reason. They agree that natural explanations are better than mythological
ones. This is what a philosophical tradition looks like. Not everyone agreeing, but everyone
engaged in the same inquiry. Not blind acceptance, but creative development. Each thinker building
on and arguing with what came before. Look at this phrase. A legacy of inquiry. That's what
Thales really gave us. Not the right answers, he got plenty of things wrong, but the right
approach, the right questions, the right attitude toward knowledge, curiosity, reason, evidence,
argument, revision. These are the tools of philosophy. These are the tools of science. And Thales
and his students were the first to use them systematically. But the Malaysian school was
just the beginning. Thales' influence rippled out far beyond his immediate students. Let's
zoom out even further and look at how Thales shaped the entire trajectory of Greek philosophy,
and by extension, Western philosophy as a whole. Because here's the thing. Every major Greek
philosopher after Thales is responding to the questions he raised and the approach he pioneered.
The slide mentions the foundations of Western philosophy. Let me break down what that actually
means. First, Thales established that philosophy is about rational inquiry into the nature of
reality, not revelation, not tradition. Not because the gods said so, but observation,
reason, and argument. Every philosopher after him, whether they agree with his conclusions
or not, accepts this basic premise. Even Plato, who believes in transcendent forms and the
immortal soul, makes arguments for these positions. He doesn't just appeal to religious authority.
Think about how radical this is. For thousands of years, human societies explained the world
through mythology. The gods did this. The spirits did that. The ancestors decreed this. Don't
question it. Thales said, question it. Question everything. Use your mind. Look at the evidence.
Make arguments. Be willing to be wrong. This is the birth of critical thinking. This is
the moment when human beings claimed the right to understand reality for themselves. And once
that door is opened, you can't close it. Once you've said, we can figure this out through
reason, you've unleashed something unstoppable. The Presocratics, Heraclitus, Parmenides, Empedocles,
Democritus, they're all following Thales' lead, asking questions about the fundamental nature
of reality. Socrates takes Thales' method of questioning and applies it to ethics and human
life. Plato takes the search for underlying unity. and develops his theory of forms. Aristotle
systematizes the whole enterprise, creating formal logic and organizing knowledge into
different sciences. But let's look at the specific questions Thales raised that are still central
to philosophy. 1. What is the fundamental nature of reality? Is there an underlying unity beneath
apparent diversity? We're still asking this. Physicists are looking for a unified field
theory. Philosophers debate Maunism versus pluralism. Same question, more sophisticated tools. 2.
How do we explain change and transformation? How does one thing become another? Still asking
this. Philosophy of science, metaphysics, even quantum mechanics, all grappling with the nature
of change and causation. 3. What is the relationship between the natural and the divine? Can we
explain the world without appealing to supernatural forces? Still asking this. The relationship
between science and religion. Naturalism versus supernaturalism. These are live debates that
trace back to Thales. 4. What can human reason discover? What are the limits and possibilities
of rational inquiry? Still asking this. Epistemology, the study of knowledge, is still exploring
questions Thales first raised about how we know what we know. You know what's kind of hilarious?
Thales would probably be terrible in a modern philosophy department. Professor Thales, your
theory that everything is water doesn't account for the atomic structure of matter the periodic
table of elements, or basic chemistry. Professor Thales, your claim that magnets have souls
is inconsistent with our understanding of electromagnetic fields. Professor Thales, we're going to need
you to revise and resubmit. But here's the thing. Being wrong about specific claims doesn't diminish
the importance of asking the right questions and pioneering the right methods. Newton was
wrong about absolute space and time. Einstein showed that. Does that make Newton unimportant?
Of course not. Darwin didn't understand genetics. Does that make evolution unimportant? Obviously
not. Thales' legacy isn't his specific theories. It's the entire framework he created for thinking
about reality. Look at this phrase again. A legacy of inquiry. Not a legacy of answers,
but a legacy of questions. Not a legacy of dogma, but a legacy of investigation. This is what
makes Thales the father of Western philosophy. He showed us that. The universe is knowable,
human reason is powerful, natural explanations are possible, questions are more important
than inherited answers. Being wrong is part of the process of getting closer to truth.
And here's what's remarkable. This tradition of inquiry that Thales started 2,600 years
ago is still alive. Every time a scientist questions a theory and designs an experiment to test
it, that's Thales. Every time a philosopher examines an assumption and asks, but is this
really true? That's Thales. Every time you refuse to accept something just because that's how
it's always been done and you ask but why, that's Thales. The questions change, the tools get
more sophisticated. Our understanding deepens, but the fundamental approach, rational inquiry
into the nature of reality, that's the same approach Thales pioneered in Meletus 26 centuries
ago. I sometimes imagine what Thales would think if he could see a modern university.
The laboratories. The libraries. The computers. The accumulated knowledge of centuries. Would
he be overwhelmed? Would he feel vindicated? I think he'd walk into a physics lab, watch
someone doing an experiment, and nod approvingly. Yes. This is what I was talking about. Observe,
measure, think, test. This is how you understand the world. Then he'd probably ask a bunch of
annoying questions about quantum mechanics and get into an argument with the physicists, because
that's what philosophers do. We ask questions, we challenge assumptions, we refuse to accept
easy answers. That's the tradition Thales started, and it's alive and well. So we've seen Thales,
the mathematician, the astronomer, the natural philosopher, the founder of a school, the father
of Western philosophy. But there's one more question we need to address. Why does any of
this matter? Why should you care about a guy who lived 2,600 years ago and thought everything
was made of water? Let's talk about the significance of Thales for us, here today. Alright, so
I've spent the last 45 minutes telling you how amazing Thales was, how revolutionary, how
foundational to everything we think and do. Now let me tell you the truth. We're not actually
sure about most of this. Welcome to ancient philosophy, where the sources are fragmentary.
The stories are probably exaggerated, and half of what we know is educated guesswork. But
here's the thing. This uncertainty, these controversies and debates, they're actually part of the story.
They're part of what makes studying Thales interesting and important. Let's talk about the elephant
in the room. How much of what I've told you actually happened? Did Thales really predict
that eclipse? Historians argue about it. Some say yes, he had access to Babylonian eclipse
cycles and made an educated prediction. Others say the story is apocryphal, added later to
make him seem more impressive. Did he really measure the Great Pyramid using shadows? Maybe,
probably. The method works, and it sounds like something he would do. But do we have definitive
proof? No. Did he really corner the olive press market to prove philosophers aren't impractical?
Great story. probably didn't happen. But it tells us something about how his contemporaries
saw him, as someone who could have done that if he wanted to. Now you might think, Professor
Leshley, if we're not sure what actually happened, why are we studying this? What's the point?
Here's the point. We're not studying Thales to memorize facts for a test. We're studying
him to understand how philosophical thinking emerged, how it developed, and what it means
for us. Whether Thales predicted the eclipse or just an eclipse, The important thing is
that people in his time believed rational inquiry could predict celestial events. That belief
changed everything. Whether he measured the pyramid or just developed a method that could
measure pyramids, the important thing is the method itself, the application of geometric
reasoning to practical problems. The stories might be embellished, the details might be
wrong, but the significance is real. The impact is undeniable. And then there's the question
of what Thales actually meant by his various claims. When he said, is water, what did he
mean? Was he talking about literal H2O? Was he talking about something more abstract? Fluidity,
transformation, the principle of change? Was he using water as a metaphor for something
else entirely? Scholars have been arguing about this for 2600 years. And you know what? They're
still arguing about it. When he said magnets have souls, was he being literal? Was he proposing
a theory of universal animation? Or was he just trying to explain magnetic attraction using
the conceptual tools available to him? We don't know. We can't know. Thales didn't leave us
a detailed philosophical treatise explaining exactly what he meant. We have fragments, second-hand
reports, and later interpretations. This drives some people crazy. They want definitive answers.
They want to know exactly what Thales thought. Exactly what he did. Exactly what he meant.
To which I say, get comfortable with uncertainty. This is philosophy. This is history. This is
the human condition. We're always working with incomplete information. We're always interpreting.
We're always making educated guesses based on limited evidence. And honestly, that's not
a bug, it's a feature. Because here's what these controversies and debates teach us. First,
critical thinking means being honest about what we know and what we don't know. It means distinguishing
between this definitely happened, and this probably happened, and this might have happened, and
this is a later legend. I could have just told you the stories as if they were unquestionable
facts. That would have been easier, more dramatic, more satisfying, but it wouldn't have been
honest. And it wouldn't have modeled the kind of thinking Thales himself pioneered. Careful,
evidence-based, willing to acknowledge uncertainty. Second, interpretation matters. The same text,
the same fragment, the same story can be understood in multiple ways. And arguing about interpretation,
really digging into what something might mean, that's how we deepen our understanding. When
scholars debate whether Thales meant literal water or something more abstract, they're not
just arguing about ancient history. They're exploring fundamental questions about the nature
of matter, the relationship between the concrete and the abstract, the role of metaphor in philosophical
thinking. Third, The past is always being reinterpreted. Every generation looks at Thales through their
own lens, asks their own questions, finds their own significance. In the 19th century, scholars
saw Thales as the first scientist, the pioneer of rational empiricism. In the early 20th century,
some saw him as a primitive thinker, still half-stuck in mythological thinking. In the late 20th
century, scholars started appreciating the sophistication of his questions even if his answers were wrong.
Now, in the 21st century, We're asking new questions. How did cultural exchange with Egypt
and Babylon influence his thinking? How does his work relate to non-Western philosophical
traditions? What can his approach teach us about contemporary epistemological debates? Same
Thales, different questions, different interpretations, and that's good. That's how intellectual traditions
stay alive, by constantly being re-examined, re-interpreted, brought into dialogue with
new concerns. You know what I think Thales would say about all these debates and controversies?
Good. You're thinking. You're questioning. You're not just accepting what you're told. That's
exactly what I wanted. Because ultimately, the point isn't to have perfect certainty about
every detail of Thales' life and thought. The point is to engage with the questions he raised,
the methods he pioneered, and the tradition he started. And that brings us to our final
topic. Alright. We're in the homestretch. We've covered a lot of ground. Mathematics, astronomy,
natural philosophy, the Malaysian school, the birth of Western philosophy, scholarly controversies.
Now let's distill this down. What are the actual, practical, applicable lessons from Thales's
life and thought? Lesson 1. Curiosity and inquiry. Thales's life is a testament to the power of
curiosity. He didn't just accept the world as he found it. He asked why. He asked how. He
asked what if. Why does the Nile flood? How tall is that pyramid? What if there's a single
substance underlying all of reality? What causes magnetic attraction? And here's what I want
you to understand. Curiosity isn't just a personality trait. It's a choice. It's a practice. It's
something you cultivate. You can go through life on autopilot, accepting what you're told,
never questioning, never wondering. A lot of people do. Or you can choose curiosity. You
can choose to ask questions. You can choose to wonder. You can choose to investigate. Thales
chose curiosity. And that choice changed the world. What will you choose? Lesson 2 The Power
of Reason Thales demonstrated that human reason is powerful enough to understand reality. Not
perfectly. Not completely. But genuinely. We can observe patterns. We can make inferences.
We can develop theories. We can test predictions. we can discover truths about the world that
aren't immediately obvious to our senses. This is huge. This is the foundation of everything
we call knowledge. But here's what often gets missed. Reason isn't just about being smart.
It's about being disciplined. It's about following arguments where they lead, even when you don't
like the conclusion. It's about changing your mind when the evidence demands it. Thales used
reason to challenge traditional beliefs. To question inherited wisdom, propose new explanations
that contradicted what everyone knew to be true. That takes courage. It takes intellectual honesty.
It takes a commitment to truth over comfort. Can you do that? Can you follow an argument
where it leads even if it challenges your beliefs? Can you change your mind when the evidence
demands it? That's what it means to honor Thales's legacy. Not just to think, but to think honestly.
Lesson 3. The Pursuit of Fundamental Truths. Thales wasn't content with surface explanations.
He wanted to understand the underlying principles, the fundamental nature of reality. This is
what separates philosophy from mere opinion sharing. Philosophy asks the deep questions,
the foundational questions, the questions that everything else depends on. What is real? How
do we know? What matters? How should we live? These aren't easy questions. They're not the
kind of questions you answer once and move on. They're the kind of questions you wrestle with
for a lifetime, but they're important questions. They're the questions that shape how you understand
yourself, your life, your place in the universe. Thales showed us that these questions are worth
pursuing, that the search for fundamental truths, even if we never arrive at final answers, is
a worthy way to spend a human life. Now let me bring these three lessons together, because
they're not really separate. They're interconnected. Curiosity drives you to ask questions. Reason
gives you the tools to pursue answers. The commitment to fundamental truths gives you direction.
It tells you which questions matter most. Together, these three things create what we might call
the philosophical life. A life oriented toward understanding. A life committed to truth. A
life that refuses to accept easy answers or comfortable illusions. And here's my question
for you. Are you willing to live that kind of life? Are you willing to be curious, even when
it's uncomfortable? Even when the questions lead you to places you didn't expect? Are you
willing to use reason, even when it challenges your beliefs? Even when it requires you to
admit you were wrong? Are you willing to pursue fundamental truths, even when they're difficult?
Even when the answers are uncertain? Because that's what Thales did. That's what every great
philosopher since has done. That's what you can do, if you choose. Now I'm not saying this
is easy. It's not. It's much easier to just accept what you're told. To go along with the
crowd. To never question, never wonder, never dig deeper. Thales could have done that. He
was wealthy. He was comfortable. He could have just enjoyed his life, made money in the olive
oil business, and never bothered with all this philosophy stuff. But he didn't. He chose the
harder path. The path of inquiry. The path of questioning. the path of seeking truth. And
because he made that choice, we're sitting here 2,600 years later, still talking about him,
still learning from him, still inspired by him. Look at these three lessons again. Curiosity
and inquiry. The power of reason. The pursuit of fundamental truths. These aren't just historical
observations about some ancient Greek philosopher. These are principles for living. These are
tools for thinking. These are commitments that can shape your entire life. Thales showed us
that a single person armed with curiosity and reason and a commitment to truth can change
the world, can start a revolution, can launch an entire tradition of thought that lasts for
millennia. He didn't have modern technology. He didn't have the internet. He didn't have
libraries full of books or universities full of scholars. He had his mind. He had his curiosity.
He had his commitment to understanding. And that was enough. So here's my final challenge
to you. You have more resources than Thales ever dreamed of. more information, more tools,
more opportunities, what will you do with them? Will you use them to pursue truth, to ask deep
questions, to understand reality more fully, or will you let them distract you, entertain
you, keep you comfortable but intellectually asleep? The choice is yours. It's always been
yours. It will always be yours. Thales made his choice 2600 years ago in Miletus. What
choice will you make today? Be curious. Be rational. Pursue truth. Be like Thales. That's the lesson.
That's the legacy. That's the challenge. Now go think about it.