How Plato and Aristotle Influenced Scientific Thought

From a lecture series presented by The Great Courses

Although Plato and Aristotle are still regarded as being among history’s greatest minds, their scientific theories may seem quaint by today’s standards. Nevertheless, a closer look at these theories reveals that they were actually quite logical. And, how does Aristotle’s account of the four earthly elements measure up according to today’s thinking?

The School of Athens. Painting by Raphael.
Plato and Aristotle in The School of Athens, by Raphael

Reexamining Rejected Scientific Theories

It’s unfortunate that science, since the end of World War II and the beginning of the Cold War, has been taught in a largely a historical fashion. During that time period, with the threat of potential nuclear annihilation, the launch of the space race, and the growth of technology use in the global economy, the emphasis of science education focused on cranking out as many qualified scientists and engineers as possible, as quickly as possible.

The history of how scientific thought evolved is valuable to study. Rejected theories can seem quaint, if not absurd, and it is worthwhile to examine why the intellectual community bought into them.

This is a transcript from the video series Redefining Reality: The Intellectual Implications of Modern Science. Watch it now, on The Great Courses Plus.

It is also helpful to see the residue of old ways of thinking. What invisible presuppositions do we still accept, despite having surrendered the worldview that produced them? Rethinking these is often the key to the route forward.

Ancient Greek Geography and Equilibrium

The birthplace of the pre-modern Western view of reality was in classical Greece. It’s truly stunning how much of an understanding the ancient Greeks had about the universe and how intricate their theories of physics, astronomy, chemistry, and biology were.

Many of us were told when we were young that in the 1490s Christopher Columbus was trying to prove that the world was round, in addition to finding a shorter route to the east. The fact remains that not only did the ancient Greeks know back in the 4th century B.C. that the Earth is round, but they also knew, to a staggering accuracy, how big it is.

The Greeks used several means to calculate the circumference of the Earth. One straightforward approach used a pole, a ruler, and lots of cleverness. At 12 noon, the Sun is at its highest point in the sky. While holding a pole vertically, it casts a shadow on the ground. But what happens if two people conduct this experiment at different places? If the world is flat, then the shadows should be the same no matter where the people stand since the angle will be the same.

But if the Earth is curved and one of the poles is north of the other, the angle changes because of the curvature of the Earth. So, the Greeks tested it, and lo and behold, the lengths were different. They had proof that the Earth was curved. Combining some intricate geometry with knowledge of how much farther north one person is, the Greeks calculated how big the Earth is—simply brilliant.

The idea of a round Earth situated itself well in the Greek view of the world. On the one hand, it squared with the observable facts. sun rises and sets in the same directions day after day. The moon rises and sets in the same directions night after night—so, too, with the fixed stars.

The repetitious motions certainly seemed circular. The idea of a round Earth with heavenly bodies moving around it in their own circular orbits seemed to make for an elegant picture.

That elegance was important to the Greeks, whose worldview was based on the concept of teleology. The word teleology comes from the Greek roots telos—which means an end, a goal, or an aim—and logos—which means reasoning, logic, or intellectual order.

Teleology is the view that all change is goal-directed, that everything happens because of an end that’s trying to be achieved. The universe, they believed, was well-ordered and striving for a goal, namely, perfection. When a thing is perfect, it’s reached its goal and will never again change, but until then, it will seek a higher state on its way to its goal.

Note that we still have plenty of remnants of this view in the way we speak about science today: matter seeks its lowest energy state; evolution selects advantageous adaptations, the economy moves towards stable equilibrium points. All of these are framed in the sort of teleological language we get from the Greek thinkers.

Learn more about reality as understood by the ancient Greeks

Plato’s Philosophy: Rejecting the Material World

Rejecting the material world is the view that led Plato to express his famous picture of reality set out in the allegory of the cave in his masterwork, The Republic. This view contends that there are two worlds, distinct realms.

Statue of Plato in front of the University of Athens in Greece
Statue of Plato in front of the University of Athens in Greece

One realm is the material world, which is ever-changing. A material thing can always change, just use a big enough sledge hammer. This means that the material world will never be perfect, always corrupted and corruptible.

The other domain, the realm of ideas is different. All material things are part of a species, a type, a kind. What defines that species is a set of essential properties.

To have real knowledge of a thing is to understand this essence, or form, as Plato called it. Wisdom comes from rejecting the imperfect representations of the forms—that is, the material things—and embracing the immaterial forms—the perfect, unchanging ideas of the things.

In Raphael’s famous painting, The School of Athens, the great thinkers of classical Greece are seen together. At the very center of the image are Plato and his student Aristotle. Plato is pointing up while Aristotle is portrayed pointing down.

Aristotle’s Essentialism

According to Plato, reality exists away from the material world, within the world of forms, which can only be viewed with the eye of the mind. Reality, for Aristotle, was right here in this world. It was Aristotle’s elevation of the material realm that launched what we think of as science.

For decades, Aristotle studied with Plato at his academy until Plato’s death, after which Plato’s lectures became intolerably boring. He knew Plato’s thoughts, inside and out, but he wasn’t a disciple.

Statue of Aristotle
Aristotle cataloged biological creatures and ordered them by anatomical properties.

While Aristotle rejected certain, important core elements, he kept some central aspects. One of the features that Aristotle shared with platonic thought—as did so many other great thinkers—was teleology.

Again, teleology is the view that everything in reality strives towards a goal, a perfect unchanging state.

While Plato viewed this perfection as being in the world of forms, a realm accessible to the mind but not the senses, Aristotle, on the other hand, put them in the observable world.

All things are a part of a species that’s defined by its essential characteristics, crucially important properties that all members of the species share. These, according to Aristotle, are internal in that every member of a species shares a certain structure of their soul. All have the same potentiality and naturally grow in the same way to actualize it.

Aristotle, thus, undertook the project of cataloging biological creatures and systematically ordering them by anatomical properties. Carl Linnaeus followed up on Aristotle’s work in the 18th century, giving us our modern taxonomy of living things.

This view of essentialism also served as the basis for Aristotle’s theories of chemistry and physics. Because of our modern atomic theory, we think of chemistry emerging out of physics, but for Aristotle, it was the other way around.

Learn more about metaphysics and the nature of science

The Four Earthly Elements

All material things are comprised of four basic elements—earth, air, fire, and water. It’s interesting that today references to these four earthly elements takes on a sort of new-age, anti-scientific feel—a sense of rejecting modern science. From our contemporary atomic view of matter, the old elements do seem kind of silly.

But it makes a lot more sense when we realize that they’re reflective of what we now call the states of matter. Earth—or soil—is solid, water is liquid, air is gas, and fire—it seems to be a thing unto itself. We now know it’s a chemical reaction—rapid oxidation. But fire has a location—fire’s in a place—and it has a size, so it seems to makes perfect sense that we would think of it as a type of thing—a fourth kind of matter.

When we said that all things were made of earth, air, fire, and water, what we meant was that all things were in one of these four states and that chemical reactions brought on by mixing, heating, or cooling could give rise to a new substance in a different state—basic chemistry.

Each of these four elements had an essence and this included a natural place, the place in the universe where it was meant to be. So when Aristotle says that Earth is at the center of the universe, he’s not making what we think of as an astronomical claim—that the planet Earth is at the center of space.

Rather, he was simply making the true claim that dirt falls. By earth, he meant soil. If a clod of dirt is in a person’s hand and dropped, where does it go? Straight down. But recall that the Greeks knew the Earth is round. If it goes straight down no matter where the person is, then it’s always moving toward the middle of a sphere.

When Aristotle says that earth is at the center of the universe, he means that soil will seek its natural resting place and remain there, and that place is at the center of the universe.

Water, too, moves straight down. Tip over a cup of water and it spills down in a line. But water’s place is not at the center. Since Greece is comprised of a peninsula and islands, the Greeks knew all about water and that dirt settles out to the bottom and water sits on top. So, the natural place for water is in a sphere around the natural place of earth.

If a person dunks their head under water and exhales, what happens? Bubbles are produced and move straight upward. Air has a natural place above water.

If a person flicks a lighter, then a small flame is produced. Turn the lighter upside down and what happens? The person’s thumb gets burned. Why? Because the flame is always going up, no matter the orientation of the source of the fire. Fire is seeking its natural place above the sphere of air.

All of the four basic elements, earth, air, fire, and water, have a natural place, and their natural state of motion is in a straight line to that place, where they then remain at rest. Motion is caused by an internal drive within the object based on its nature.

From the lecture series Redefining Reality: The Intellectual Implications of Modern Science, taught by Professor Steven Gimbel

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