Pre-Socratics: A Painless Introduction

Pre-Socratics: A Painless Introduction

A Painless Introduction

This is a short book about pre-Socratic philosophers for people who care more about the central questions of philosophy themselves — What exists? How should we live? How can we know? — than they do about the historical matter of pre-Socratic thought. But current research in philosophy often refers to the work of pre-Socratic philosophers, so it is worth knowing a bit about what they thought. My book explains the bare essentials about pre-Socratic philosophy you must understand to do philosophy today.

This book does not assume you know much about philosophy. It does not discuss every aspect or interpretation of a philosopher’s work. It will only tell you what you need to know to engage with philosophy today.

My main sources are the histories of philosophy by Kenny, Russell, and Copleston (of whom you will hear echoes below), along with translations of the original works.

Before Socrates

If one wishes to take an ecstatic view of “the Greek miracle,” it is supplied by Bertrand Russell in A History of Western Philosophy:

What [the Greeks] achieved in art and literature is familiar to everybody, but what they did in the purely intellectual realm is even more exceptional. They invented mathematics [other cultures had rules of thumb, but Greece invented deduction from axioms] and science and philosophy; they first wrote history as opposed to mere annals; they speculated freely about the nature of the world and the ends of life, without being bound in the fetters of any inherited orthodoxy. What occurred was so astonishing that, until very recent times, men were content to gape and talk mystically about the Greek genius.

This, then, is our subject: the birth of philosophy in Ancient Greece.

The three fathers of Western Philosophy are Socrates, Plato, and Aristotle. They are so important that all philosophers before them are lumped under one heading: the “pre-Socratics.”

The Milesian School

In the ancient world, philosophy and science blurred together. Thinkers had to “philosophize” about astronomy and medicine more often than they could conduct rigorous tests in those fields. This was for much the same reason we must now philosophize a great deal about the mind until the tools of neuroscience improve.

Thus, the first person we call a “philosopher” is Thales (624-546 B.C.) of Miletus, who was really a physicist and astronomer, except that he had no scientific method or scientific instruments, so he had to philosophize his way to conclusions about the physical world.

Many people at the time assumed that earthquakes and many other events were the acts of the gods, but Thales was one of the first people in recorded history to seek natural explanations instead. He thought the earth floated on water, and earthquakes resulted when waves rocked the earth.

After seeing some moisture turn into air, slime, and earth, he came to believe there was an original substance from which all else is formed — an arche — and that this arche was water. Many others followed him in this approach, proposing other basic elements such as air. If it turns out that string theorists are right and everything is made of subatomic vibrating strings, then Thales’ basic idea is correct, though he guessed the arche incorrectly.

Thales was also skilled at geometry, and is reported to have measured the height of the pyramids by the lengths of their shadows, and to have measured the distances of ships at sea with sticks at two different points on land.

He is famous for predicting a solar eclipse in 585 B.C., though he probably borrowed this skill from the Babylonians, who had been predicting eclipses for hundreds of years.

What historians think is unique about Thales is the universality of his approach. Thales sought universal, rational, natural explanations for the world instead of mythological ones. That is why we call him the first philosopher.

Anaximander (610-546 B.C.) was even more insistent to explain everything in terms of physical forces, and may also have been the first philosopher to write down his ideas, and the first to conduct a scientific experiment.

He believed the arche was an infinite, indefinite mass (apeiron) from which everything came, much like the primordial Chaos of Greek mythology. This was perhaps an improvement on Thales’ view that water was the original element, for water cannot account for the diversity of nature. For example, water is only wet and never dry. So the arche must be more basic than water, fire, earth, or air.

Anaximander thought the earth we observe is the flat top of a cylinder, floating still in a vast void. He took note of fossils and proposed that animals had originally come from the sea, and humans had come from those animals. But he had no concept of natural selection.

Anaximenes (585-528 B.C.) continued to seek natural, unifying explanations. He proposed the arche was air, and that things varied only in their density. Fire was diffused air, while water was condensed air, and earth was air condensed further still.

Perhaps he rejected Anaximander’s apeiron proposal because the notion of an indefinite, unlimited substance is unintelligible to us, and is really no better an explanation than an origins myth involving gods and chaos, as described by the poet Hesiod (8th century B.C.). Anaximenes may have proposed air as the arche because it is intelligible and observable, and seems like it could be in everything, including rocks and trees and people.

Xenophanes (b. 570 B.C.) followed the Milesian School and believed all things were made of earth and water. He may be best known as a critic of polytheism, writing:

Mortals deem that gods are begotten as they are. The Ethiopians make their gods black and snub-nosed; the Thracians say theirs have blue eyes and red hair.

Following several arguments, he concluded that God is one, eternal, non-anthropomorphic being. For Xenophanes, God is not much of a person, but rather the arche. He has no parts, and need not physically contact the world, but “remote and effortless, with his mind alone he governs all there is,” like the God of Medieval perfect being theology.

Whereas the Egyptians and Hebrews had, at different times, proclaimed monotheism by divine revelation, Xenophanes was the first to arrive at an abstract monotheism by argument. He was the first natural theologian.

The Milesian philosophers were wrong about everything, but they asked the right questions, and for the first time sought natural explanations for the world.


Pythagoras (late 6th century B.C.) was born on the Greek island of Samos. He traveled widely and then settled in Southern Italy, where he founded a society of disciples. After his death, magical powers were attributed to him and a religion formed. Among its commands were to not eat beans, to not step over crossbars, and to not look in mirrors near a light.

The Pythagoreans often attributed their own views and innovations to their founder, so it is easier to say what the Pythagoreans believed than to say anything about Pythagoras himself. The Pythagoreans, then, said that “all is number,” by which they meant that number was in everything. They had discovered the mathematical nature of music and harmony, and the numbers inherent to many shapes. Of course, they are best known today for the Pythagorean Theorem about right-angle triangles.

Their most important influence was on Plato, and through Plato, on all of Western philosophy. Pythagoreans had a mystical reverence for the perfection of abstract mathematical thinking, and deemed it a firm foundation for philosophy. This confidence lay at the heart of Plato’s philosophy, as did the Pythagorean notion of a perfect, eternal world revealed to our minds but not our senses. This emphasis on mathematical reasoning, developed further as deduction from self-evident axioms to non-obvious conclusions by Euclid (b. 300 B.C.) and others, came to dominate much of Western philosophy and theology through Plato, Augustine, Aquinas, Descartes, Spinoza, Kant, and Newton.

Plato also borrowed from the Pythagoreans an emphasis on the soul and its thoughtful care, and perhaps even its tripartite nature.

The Pythagoreans also defended the immortality of the soul, though they believed that after physical death the soul did not travel to an alternate world, but returned to the present one in a different body, and not necessarily a human one. Pythagoras himself said he could remember fighting as a hero centuries earlier at the siege of Troy.

Heraclitus and Parmenides

Heraclitus (535-475 B.C.) of Ephesus thought the world was unified by a kind of harmony that resulted from strife between opposites: health and illness, good and evil, day and night. The world, he thought, was dominated by a cosmic justice that prevented one opposite from overcoming the other.

He was the most pithy and quotable of the pre-Socratics. Among his one-liners are: “Donkeys prefer straw to gold” and “Man’s character is his fate” and “Swine wash in the mud, and barnyard fowls in the dust.” Heraclitus was enamored with his own prose, and wrote as a prophet proclaiming the Word of Heraclitus.

Heraclitus seems to have recognized the problem faced by the Milesian school: If the arche is unmoving and eternal, then how do we explain the leap from unmoving being to the dynamic becoming we see all around us? Heraclitus’ solution was to remove being altogether. He said that everything is always changing: “You cannot step into the same river twice, for new waters are ever flowing in upon you.”

Parmenides (510-440 B.C.) of Elea offered the opposite solution. He rejected becoming altogether in favor of motionless being. He thought that nothing ever changes. Our senses give us nothing but illusion, and everything is really The One — a kind of perfect sphere that cannot be divided. Everything that exists has always existed and will always exist. This doctrine is similar to the “block universe” theory of modern physics, according to which time does not “flow” but instead the past and present and future all exist, but in different directions, like backward and forward. Arguing against this theory, Karl Popper exclaimed to Einstein, “You are Parmenides!”

More important than Parmenides’ metaphysical claim itself is that he gave an argument for it. He appears to have argued something like this: When you think and speak, you think and speak about something. But you can think and speak about some thing at one time as well as another. So whatever you can think and speak of must exist at all times. So there can be no change, for change consists of things beginning to be or ceasing to be.

This argument is obviously flawed, for we often use words to speak of things that do not exist (unicorns) or things from the past (Shakespeare) or the potential future (interstellar spacecraft).

But notice that Parmenides gave an argument from the way we use thought and language to a conclusion about the external world. He may have been the first to do so, and this method has since been used by most of the prominent metaphysicians in history, though many today doubt its usefulness.

Because he initiated the purely rational method of inquiry about reality, and therefore opened the debate between rationalism and empiricism that would later dominate so much of the history of philosophy, and because he was the first epistemologist in that he clearly distinguished belief from knowledge, Parmenides is often named the most important philosopher before Socrates.

Heraclitus and Parmenides mapped the battlefield for centuries of philosophical struggle. It was of central importance to Democritus, Plato, Aristotle, and others to reconcile being and becoming.


Zeno (490-430 B.C.) of Elea — not to be confused with Zeno of Citium, the founder of Stoicism — is today best known for his paradoxes, which have challenged, infuriated, and inspired some of philosophy’s greatest minds down to the present day.

His arguments may be the earliest examples of reductio ad absurdum, a form of argument in which one tries to disprove a proposition by showing that it logically leads to absurdity. Zeno used several reductio ad absurdum arguments in defense of Parmenides’ doctrine that “all is one” and that change is impossible.

Of Zeno’s nine surviving paradoxes, two are of most interest. They are: (1) Achilles and the tortoise, and (2) the flying arrow.

The paradox of Achilles and the tortoise goes like this: Achilles and the tortoise are in a footrace, and Achilles gives the tortoise a head start of, say, 100 meters. Both start running at a constant speed, with Achilles running faster than the tortoise. After some time, Achilles will have run 100 meters and caught up to the tortoise’s starting point, and in the meantime the tortoise will have progressed some shorter distance: say, 10 meters.

It then takes Achilles some time to cross those 10 meters, by which time the tortoise will have moved a bit further ahead. And so on. So whenever Achilles reaches the point where the tortoise was most recently, he still has further to go! And so Achilles can never catch up with the tortoise. And yet experience tells us that Achilles can easily pass the tortoise. Hence the paradox.

The flying arrow paradox arises from divisions of time rather than divisions of space. Zeno notes that for motion to occur, an object such as a flying arrow must change positions. In any given instant of time, for the arrow to be moving it must either move to where it is, or move to where it is not. But it cannot move to where it is not, because we are considering only a single instant of time. And it cannot move to where it is, because it is already there. Thus at any given instant of time, the arrow is not moving. Therefore the arrow cannot move at any instant of time, meaning it cannot move at all.

There have been many proposed solutions to these paradoxes. Thomas Aquinas (b. 1225) and Peter Lynds (b. 1975) argued against the arrow paradox by claiming that time is not composed of instants. In 1958, Hans Reichenbach argued that given general relativity, according to which time and space are not separate entities, the paradox might dissolve. In 1987, Jean Paul van Bendegem offered a solution by denying Zeno’s assumption that between any two given points in space or time there is always another point.

But as with Parmenides, the influence of Zeno is not so much with his arguments as with their novel form. Moreover, Zeno may have been the first person to practice the “dialectic” made famous by Socrates: that practice of two or more people exchanging arguments and counter-arguments, ending in a refutation of one view or perhaps a synthesis of both views.


Empedocles (490-430 B.C.) is perhaps best known for two scientific discoveries involving buckets. First, he noticed that if you push an upside-down bucket under water, the water does not rush in to fill the bucket. Thus, he discovered that air is its own, separate substance. Second, he noticed that if you swing a bucket of water around on a rope above your head, the water does not fall out of the bucket. Thus, he discovered centrifugal force.

Empedocles thought that the original elements were earth, fire, air, and water, which when combined in different ways result in everything we see. But there must be active forces that cause these elements to be combined in various ways, and these forces are Love and Strife. Despite their names, Empedocles thought of these as physical forces: Love attracted elements together to form objects, and Strife pushed them apart and decayed objects. This cycle proceeded by chance and physical necessity rather than by cosmic purpose.

He also defended a fantastical version of evolution by natural selection. His theory, as paraphrased by Bertrand Russell, was that:

Originally, “countless tribes of mortal creatures were scattered abroad, endowed with all manner of forms, a wonder to behold.” There were heads without necks, arms without shoulders, eyes without foreheads, solitary limbs seeking for union. These things joined together as each might chance; there were shambling creatures with countless hands, creatures with faces and breasts looking in different directions, creatures with the bodies of oxen and the faces of men, and others with the faces of oxen and the bodies of men. There were hermaphrodites combining the natures of men and women, but sterile. In the end, only certain forms survived.

Aristotle derided Empedocles for replacing teleology with chance, and the world followed Aristotle for 2,000 years. But Empedocles had the last laugh when Darwin commended him for “shadowing forth the principle of natural selection.”


Anaxagoras (500-428 B.C.) brought philosophy to Athens, the city which later produced Socrates and Plato. He prefigured modern Big Bang theory. He held that the universe was originally infinitely dense and small. This primeval pebble rotated, throwing off air and ether that later formed stars and planets and everything else. This expansion and separation of things is not complete, and will continue forever. Thus, every thing contains at least a tiny bit of every element, but we call it by the element that predominates. So fire contains some stone, but it appears to us as fire because it is mostly fire.

The exception is mind (nous), which exists only in living things, and is the cause of all motion. Aristotle complained that Anaxagoras tried to offer a natural explanation for everything, except that whenever he couldn’t explain something he put “mind” into the gap. Anaxagoras proposed a “mind of the gaps” just as many theologians proposed a “God of the gaps.” But Plato was attracted to Anaxagoras’ idea of mind.

Anaxagoras was eventually banished from Athens, perhaps because he said the sun was a fireball rather than a god.


Democritus (b. 460 B.C.) prefigured the findings of modern science most completely. He believed that everything is made of atoms that are physically indivisible, that there is empty space (void) between atoms, that atoms are always in motion, that atoms are indestructible, and that there are many kinds of atoms.

According to him, atoms form different substances based on their shape. Iron holds together firmly because its atoms have hooks. Water flows because its atoms are smooth and slippery. Salt has a sharp taste because its atoms are pointy. And so on. All atoms interact mechanically, and thus the whole world is a machine, with no need for gods or a Prime Mover or a “final cause” of the universe.

Democritus was a strict determinist. He did not believe in chance, but rather thought that everything proceeded due to natural laws. Even thought and the soul were made of atoms and governed by natural laws.

He also believed in multiple worlds: some without sun or moon, some with larger sun and moon, some without animals or plants or moisture. All this resulted from the random motion and collision of tiny atoms, which joined each other according to their shape.

Democritus’ epistemology is unclear, for he used sense data to construct his theory of atoms, and yet he rejected the senses as but sources of illusion, and proclaimed atoms and the void as the only true reality we could know. So perhaps Democritus should have been a skeptic about knowledge, as was his student Metrodorus, who wrote:

None of us knows anything, not even whether we know or do not know, not even what knowing and not knowing are.

Democritus was also the first philosopher to offer a systematic morality. Happiness was to be found in a life of cheerfulness and quiet contentment. Moderation is good, but asceticism is not. The trick is to choose the right times for fasting and feasting. In placing happiness at the center of ethics, Democritus set the agenda for many Greek ethical systems to come. But he did not mention that other ground of Greek ethics: virtue.

Final Thoughts

Now that we have discussed the pre-Socratic philosophers of Ancient Greece, we might ask: “What about the ancient philosophers of other cultures? Did philosophy really have only one birth in all the world, in Greece?”

Certainly, other ancient cultures had “philosophies” in that they held assumptions about what existed, what we should do, and how we can know. Educated men developed and discussed these assumptions, and sometimes wrote down their innovations.

Pre-Socratic philosophy’s greatest competitor is Ancient Indian philosophy — another wellspring of mathematics, science, dialectic argumentation, and materialism. That is a subject for another book, but it is clear that as a matter of history, the marvels of Western science and philosophy that have so profoundly transformed the modern world descended from the work of Ancient Greeks, not Ancient Indians.

The birth of philosophy is shrouded in the mists of the ancient past. What little is preserved of these early thinkers’ works is preserved mostly in quotations from their opponents, which can hardly give us an accurate view of their positions. Moreover, we may never know who really invented method X or who first defended theory Y. All we can say is that so-and-so is the earliest person known to have used method X or defended theory Y.

But however inaccurate and incomplete our picture of pre-Socratic philosophy may be, it seems that some extraordinary progress was made in Ancient Greece. Here were the first and most elaborate attempts to explain the world in a unified and mechanical way. Here were the origins of geometry as deduction from self-evident axioms to non-obvious conclusions. Here were invented new methods of argument and scientific discovery.

Moreover, the pre-Socratics set the stage for the revolution to come in Socrates and Plato.


The End