10 Greek Philosophers Who Shaped The World

The foundational ideas laid down by great thinkers such as Socrates, Plato, and Aristotle still influence our understanding of the world today. These brilliant scholars began to use reason and logic to try and unravel the workings of the cosmos. They also explored the intricacies of human morality. But who were these ancient Greek philosophers? And what were their key ideas? From presocratics like Thales of Miletus to Plato and Aristotle, we’ll discuss the famous thinkers that guided philosophy and science for thousands of years. We’ll also explore the three main schools of Hellenistic philosophy and the founders that governed philosophy after Alexander the Great. Here are the ten most famous Greek philosophers who shaped the world for centuries.

During the 7th Century BCE, philosophy dealt more with natural science rather than moral questions.  One of the first Greek philosophers to concentrate on scientific thought was Thales of Miletus. Thales was born around 624 BCE in the city of Miletus in Asia Minor and was part of the new wave of thinkers trying to determine how the cosmos was constructed. This was the philosophical branch of metaphysics. Thales was a Monist, meaning that he considered a single element to be the main building block of the cosmos.

Thales reached this hypothesis by considering what a cosmological building block would need to be. He determined that it should be capable of changing and moving. It had to be essential to life, and it had to be something from which every part of the universe could be made. In his observations, Thales decided that water could fill all these criteria.

Thales was one of the first thinkers who began to consider explanations about the natural world that didn’t rely on the Gods. This early form of rational reasoning made Thales one of the most influential Greek philosophers. He founded the Milesian School, and his successors eventually taught pupils like Pythagoras.

2. Heraclitus

“Panta rhei” or “everything flows,” captures the essence of Heraclitus’s philosophy of constant change, conceived in the late 6th century BCE. Heraclitus of Ephesus believed that the universe is in a perpetual state of flux, with nothing remaining static. This ongoing transformation is driven by the unity of opposites, where conflict and tension paradoxically create balance in the cosmos. Unlike earlier philosophers like Thales or Pythagoras, who sought a permanent, unchanging reality, Heraclitus rejected the notion of a static cosmos. Instead, for him everything was in a state of becoming, with the universe continually evolving. This idea is famously reflected in a statement attribute to Heraclitus (but probably never spoken by the philosopher): “You cannot step twice into the same rivers,” as both the river and the individual are constantly changing. Every passing moment finds a new world and a new “us.”

Though Heraclitus emphasized the constant flux, he also believed in the existence of the Logos, a rational principle that governs the universe and maintains order. While everything is subject to change, the Logos ensures order and coherence. Heraclitus argued that most people are unaware of this deeper, unifying force that connects all things. The wisdom thus lays in recognizing and accepting the ever-changing nature of the universe and the underlying harmony it conceals.

Ultimately, Heraclitus challenged traditional views on stability and permanence. His philosophy of flux, the unity of opposites, and the Logos significantly influenced later thinkers, especially the Stoics, shaping the development of metaphysical thought in Western philosophy.

Pythagoras was part of the next wave of presocratic Greek philosophers and he is thought to have been born on the island of Samos in 570 BCE. Pythagoras believed mathematics offered a harmonious and rational way of explaining the workings of the cosmos.

He hypothesized that everything in the universe was governed by the principles of mathematics and considered the discipline to be the foundational model for philosophy. He discovered the complex relationships between numbers in the form of proportions and ratios, a line of thinking that was reinforced by his observations of sound and harmonics.

Pythagoras studied geometry and made several stunning discoveries that would eventually influence architecture and mathematics for thousands of years. He was one of the first ancient Greek philosophers to use deductive reasoning to make his conclusions, which was a monumental shift in how thinkers formed theories.

Pythagoras’ methods influenced later Greek philosophers such as Plato, and Pythagoras founded his own academy in Italy. This took the form of a commune but may have been seen as a cult, as Pythagoras imposed strict rules about diet and behavior. The Pythagoreans attached spiritual significance to numbers, and Pythagoras may have considered his philosophical revelations to be divine insights.

4. Protagoras – The Relativist Greek Philosopher

One of the first Greek philosophers to shift focus from the natural world to human issues was Protagoras. Born in 490 BCE, the year of Darius the Great’s failed conquest of Greece, Protagoras became a legal counselor during Athens’s golden age. He even became an adviser to Pericles.

Protagoras’s experience as a lawyer taught him a fundamental principle; every argument has two sides, and both may hold equal validity. This introduced the idea of subjectivity to the concept of belief. For Protagoras, it was the character of the person who held a belief that determined its worth. To illustrate this, he coined the phrase “man is the measure of all things.”

Because he believed that everything was relative depending on your individual point of view, Protagoras considered that absolute truth was unattainable. This is because what one person might consider to be true, another will believe to be false. Protagoras also believed this dichotomy was present in questions of good and evil.

This is the founding principle of Relativism and it was perhaps the first time that an ancient Greek philosopher had examined issues relating to human behavior and morality.

Socrates is one of the most famous Greek philosophers in history, and his thirst for knowledge changed the course of philosophy forever. Socrates was born in 469 BCE and he served in the Peloponnesian War. Socrates believed that knowledge was the ultimate good and that pursuing knowledge was vital to living a good, virtuous life. Socrates argued that good and evil were absolute and that only through pursuing knowledge can we learn the difference. To Socrates, ignorance was the ultimate evil.

Socrates developed the Socratic Method, which involved taking someone’s basic idea and asking a series of questions to expose any contradictions or flaws. Socrates hoped to examine everyday concepts that people took for granted so that he could gain valuable insights.

This inductive examination didn’t always go down well, and Socrates was accused of corrupting the youth of Athens. During his trial, Socrates accepted the guilty charge rather than embracing ignorance. He declared that “the life which is unexamined is not worth living” before drinking hemlock poison.

Socrates’s ideas endured because his pupil, Plato, made Socrates the central character of his dialogues. Through these writings, the Socratic Method survived to become the core tenet of scientific reasoning for centuries.

6. Plato – The Most Famous Ancient Greek Philosopher

Alongside Socrates, Plato was a founding figure of Western thought. Born in 427 BCE, Plato was a prolific writer. Through books like the Republic and the Symposium and the founding of his Academy, Plato’s ideas survived to influence generations of thinkers.

Plato theorized that a transcendent World of Ideas contained the perfect Forms of every object on Earth. When we see a table in our physical world, it is an imperfect copy of the Form of a table. To illustrate this, Plato used the “Allegory of the Cave”. A group of humans are imprisoned in a cave. Behind them blazes a fire that casts shadowy objects onto the wall in front of them while hiding the true Forms of the objects themselves. These illusions represent our fallible human senses, but Plato believed that our knowledge of Perfect Forms was also innate to us. It was only through reason that we could unlock this true knowledge.

Plato believed that this contrast between the Ideal Forms and our imperfect copies also applied to concepts such as Goodness and Justice. Plato suggested that using reason to reveal the perfect Form of Goodness, instead of our imperfect copy, was the ultimate purpose of philosophy.

At 17 years old, Aristotle studied under Plato at the Academy. After disagreeing with some of Plato’s ideas, Aristotle left to form his own school, the Lyceum. He also tutored Alexander the Great and was one of the first ancient Greek philosophers to have his ideas translated into Arabic.

Like Plato, Aristotle wanted to figure out how we attain knowledge. However, Aristotle rejected Plato’s theory of the Forms in favor of a more empirical approach. Aristotle believed we gain knowledge from the evidence that we observe in the world around us.

Aristotle theorized that when we observe a dog, we take note of the common characteristics it shares with other dogs. He also developed a form of logic called the “syllogism” to analyze two or more ideas to generate a conclusion. He saw this as a product of mankind’s innate ability to use reason, which separated us from other animals.

Aristotle was also concerned with the purpose of things and how we could lead a good life. He argued that when we recognize our positive characteristics, we should use them to pursue virtue and achieve our potential. According to Aristotle, this would bring us happiness and constitute a “good” life.

8. Epicurus – The Seeker Of Tranquility

After the death of Alexander the Great, the focus of philosophy moved away from epistemology and metaphysics and instead focused on personal ethics. Philosophical schools sprang up across the Hellenistic World. One of these was The Garden, founded by the Greek philosopher Epicurus.

Epicurus saw pleasure as the ultimate example of good, while pain was the foremost example of evil. Concepts such as justice and virtue come from pleasure. Epicurus believed that we should focus on maximizing pleasure in our lives while avoiding pain. The ultimate goal was to achieve tranquility, or what Epicurus called “ataraxia.”

Opponents of Epicurus denounced him as a seeker of hedonistic and immoral pleasures. On the contrary, Epicurus considered friendship to be the highest form of pleasure. Epicurus’s followers weren’t just students, but friends as well, sharing a simple life of easily sustainable pleasures. Ethically, Epicurus believed that to live a pleasant life, one had to be honorable, just, and wise.

Epicurus saw the fear of death as the main opposition to a life of pleasure and tranquility. He argued that we need not fear death because there is no pain involved on either a conscious or physical level. We simply cease to exist.

One of the most extreme ancient Greek philosophers was Diogenes, the founder of the Cynic school. Influenced by Socrates, Diogenes pursued a life of virtue. However, his methods were vastly different from those of other philosophers.

Diogenes believed that by rejecting material possessions and committing to an ascetic life of poverty, one could be free of social expectations and politics. He advocated living a life ruled purely by natural impulses without restrictive social conventions. For Diogenes, “he has the most who is most content with the least.”

Often mocked by other ancient Greek philosophers, the Cynics got their name from the Greek word “kunikos” which translates as “dog-like.” In many ways, this was true. Diogenes argued that we should live according to our natural animal state and allow ourselves to be governed by the rhythms of nature.

But being free from social conventions and expectations, Diogenes did not care what others thought of his philosophy. Famously, Alexander the Great sought out Diogenes and asked if there was anything he could do for him. The Cynic merely looked at the young conqueror and requested that he stop blocking his sunlight.

10. Zeno Of Citium – First Of The Stoic Greek Philosophers

One of the most widespread schools of thought founded by the ancient Greek philosophers was Stoicism. This practical philosophy was first developed by Zeno of Citium. Zeno studied under Diogenes the Cynic but took issue with some of his mentor’s more extreme ideas. So, he struck out on his own.

The main tenet of Stoicism is accepting what is not under your control. Zeno believed that by accepting what was not in our power we could dedicate our attention to what we did have power over. He believed in a divine “Logos” or lawmaker who presided over natural laws. Humans, Zeno argued, had been given free will.

By using our free will to accept what we cannot control, Zeno believed that we could work towards cultivating a “life in accordance with nature”. This refers both to living in harmony with the natural world and accepting our inherent human nature. In both instances, we should accept both the good and bad aspects of life.

Stoicism was developed further by Greek philosophers like Chrysippus but truly began to flourish during the Roman period. The famous philosopher-emperor, Marcus Aurelius, was a student of Stoicism along with writers such as Epictetus and Seneca.

Originally published: June 27, 2021. Last update: September 16, 2024, by Vedran Bileta.