The Birth of Philosophy: The Presocratics

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  • 4:35 The Monists
  • 6:21 The Pythagorians
  • 7:58 Heraclitus
  • 8:55 The Eleatics
  • 11:45 The Pluralists
  • 13:54 The Atomists
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Lesson Transcript
Instructor: Max Pfingsten
This lecture covers the advent of philosophy. It first differentiates philosophy from religion, drawing parallels to modern science. It then establishes the basic questions of Presocratic philosophy: What is matter? and What causes change? The rest of the lecture demonstrates how these questions developed as they were tackled by generations of Presocratic philosophers. Finally, it makes plain our incredible debt to the Presocratics.

Observing Reality Around Us

Look out the window at the world around you. What do you see? Whether you said the curtains, a dog, trees or the sun, what you're talking about is matter. Now look harder at those things you saw. What are those things doing? The curtain billows in the breeze. The dog scratches itself. The trees grow. The sun shines as it moves across the sky. All this moving, growing, billowing and scratching are examples of change. As you reflect on what you see, you might wonder 'What is matter?' and 'What are all these things made of?' You might also wonder 'What causes these changes?'

If you were an ancient person, you would look to religion to answer these questions. The sun is the god Helios, driving his fiery chariot across the sky. As a modern person, you know that this answer is wrong. The sun is a gigantic fusion reactor, floating in the void of space. It only appears to move across the sky because the earth is spinning beneath it.

So, what differentiates our modern understanding of the sun from the ancient one? The ancient perspective looks to religion for explanations. Religious explanations tend to be rather inflexible things, so people end up believing ridiculous things for centuries, like the sun is a fiery chariot or a dung beetle pushing a giant flaming turd across the sky. Despite the fact that no one has seen any horses or beetles (at least, not sober).

By contrast, we look for our explanations in nature, in forces we can perceive and understand. Though none of us has ever been to the sun, we can observe similar phenomena here on earth. After observation, we can come up with general rules about nature. We can then apply what we learned about nature on earth to make conjectures about the sun. Moreover, we're not married to any specific theory. 'The sun is fire' is not a law or a dogma; it's just an idea. And because it's just an idea, we can identify problems with it:

  • How could a fire's heat reach so far?
  • How can you have a fire in a vacuum?
  • How come the sun doesn't burn out?

Because we subject our theories to critical analysis, false explanations can be refuted. And as we take in new observations, we can come up with new theories to overcome these problems, making refinements along the way. In short, by observing nature, we can understand how it works. We can explain the universe, not by reference to the divine, but by reference to the mundane experiences and observations that make up our lives. Today we call this process science. In ancient Greece, they called it philosophy. The word 'philosophy' is composed of the Greek word philos, meaning 'love of,' and sophia, meaning 'wisdom.' Philosophy is literally the 'love of wisdom.'

The Presocratics

When we think of Greek philosophy, our minds leap immediately to Socrates, Plato, and Aristotle. Yet Greeks had been engaging in philosophy for nearly 200 years before Socrates was born. These philosophers are known today as the Presocratics. Presocratic philosophers attempted to tackle the same questions we began this lecture with: 'What is the universe made of?' and 'Why do things change?' These questions seem to have begun as a matter of linguistics rather than science.

The heart of the problem was the word esti, the Greek word for 'to be.' If the sun is gas, then the sun is not a man in a chariot. If the sun is here, then the sun is not there. These may seem like perfectly logical statements to us, but logic had not yet been invented when the first philosophers began writing in 600 BCE. What upset the Presocratics was not so much whether the sun was a gas or a man in a chariot; no, what worried the Presocratic philosophers was that the sun both is and is not. It seemed wrong to the Presocratics for the sun, or anything else, to not be. Everything must be something at all times, no matter what changes we might see.

The Monists

Thales was a monist who believed everything was made of water
Thalesisis notisnot beingisis notisconstant

For Thales' student, Anaximander (610-546 BCE), the constant could not be something with set characteristics, like water. Instead, he argued that the universe was made up of some stuff without any characteristics at all and that matter gains its characteristics (hot and cold, hard and soft, wet and dry) from being separated from this undefinable whole.

Anaximander's student, Anaximenes (585-528 BCE), decided that this stuff without qualities was air. The other basic elements, earth and water, were made by compressing air, while fire was made by spreading air out thinly.

We call these first three philosophers the Monists because they believed the universe to be made of just one material. They are also called the Milesian School because they all came from the city of Miletus.

The Pythagorians

Meanwhile, on the Island of Samos, Pythagoras (582-496 BCE) proposed a very different constant for the universe: numbers. We all remember Pythagoras for his famous theorem, a^2 + b^2 = c^2, but Pythagoras was not trying to help you calculate the sides of a right triangle when he came up with this theorem. He was trying to explain a basic constant in the universe. He would demonstrate this constant like this:

Pythagoras would have a person draw a right triangle. He would then use tiles to make a square on each side. (This is where we get the word 'squared.') He'd then have people count the number of tiles on each side, and lo and behold, the number of tiles on the hypotenuse always equaled the sum of the tiles from the other two sides. Pythagoras had realized through doing this over and over and over again that no matter the size or shape of the right triangle, the number of tiles in the squares of the sides always equaled the number of squares on the hypotenuse. While the many triangles we perceive might seem different, they all follow the same constant rule.

This was not the only constant Pythagoras discovered. Pythagoras was also the first to explain the mathematical ratios of music. No matter how long a string is, another string, one-sixth its length, would produce a chord. Realizing that these sorts of ratios pop up everywhere, Pythagoras supposed that numbers and ratios were the main constants of the universe.

Pythagoras noticed a number of constant mathematical ratios in the universe


Heraclitus of Ephesus (535-475 BCE) had a very different idea. For Heraclitus, the only constant was change. He believed the opposing forces of the universe were constantly trying to tear the world apart. These opposites were only held together by natural law, or logos. He compared this to the two ends of a bow pulling away from each other. This pulling is meaningless on its own. Left to their own devices, the two opposing ends will just make a worthless stick. Yet held together by the string of natural law, they make a powerful, dynamic tool. Like Pythagoras, Heraclitus had decided that the constants of the universe were not in matter itself, but rather in how matter behaves. From him, we received the adage 'All things change, so that all things may remain the same.' His ideas would later be revived in chaos theory.

The Eleatics

Directly opposed to Heraclitus was Parmenides of Elea (510-440 BCE). Parmenides was so hung up on the is/is not problem that he denied all change or difference in the universe. His work is some of the most difficult to understand, but basically, he postulated that the entire universe was one giant sphere of unidentifiable stuff. In this, he copied Anaximenes in thinking that to have the characteristics of everything, the main stuff of the universe had to have no characteristics of its own. Yet Parmenides went further by denying that this stuff ever broke up to form other things. For him, the universe just is. It never was not. It always will be. To suggest that an apple is different from an orange is to say that the apple is not an orange, and this is not acceptable. He also insists that things cannot move. To say that the apple falls from a tree is to say that the apple is not on the tree any longer. Of course, to believe in Parmenides' account, one must ignore all the evidence of one's senses. This might not seem very scientific, but it is certainly philosophical. Parmenides' philosophy would have lasting implications on future philosophy, by placing ideas on a higher order than observation.

Another resident of Elea, Zeno (490-430 BCE), attempted to demonstrate Parmenides' theory with a series of paradoxes. In these paradoxes, Zeno tried to prove that things like change and motion were impossible. A single example should suffice:

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