Aristotle was an ancient Greek philosopher and scientist born in 384 B.C. in Stagira, a small city in Macedonia. He is widely considered one of the most influential thinkers in Western history, with contributions spanning logic, biology, ethics, politics, and physics that shaped intellectual life for nearly two thousand years. He died in 322 B.C. at the age of 63.
Early Life and Education Under Plato
At 17, Aristotle left home and traveled to Athens to study at the Academy, the famous school run by the philosopher Plato. He stayed there for nearly twenty years, first as a student and later as a teacher. When Plato died in 347 B.C., Aristotle left the Academy. He publicly cited disagreements with the school’s heavy emphasis on mathematics, though he was likely also frustrated that Plato had appointed his own nephew as successor rather than Aristotle.
Tutor to Alexander the Great
In 343 B.C., King Philip II of Macedon hired Aristotle to tutor his 13-year-old son, Alexander. For roughly three years, Aristotle taught the future conqueror subjects including ethics, politics, and rhetoric. Alexander went on to build one of the largest empires in ancient history, though historians debate how much of his worldview was shaped by Aristotle’s teaching. The relationship gave Aristotle political connections and resources that would prove useful for the rest of his career.
The Lyceum and the Walking School
In 335 B.C., Aristotle returned to Athens and founded his own school, the Lyceum. It became known as the Peripatetic school, a name derived from the Greek word for “walkway,” referring to the covered paths where members gathered and discussed ideas. A popular legend holds that Aristotle himself lectured while walking, though the name more likely just comes from the physical layout of the grounds.
The Lyceum functioned as both a teaching institution and a research center. Aristotle and his students collected specimens, gathered data on animal anatomy, compiled the constitutional histories of Greek city-states, and systematically investigated questions across dozens of fields. It was one of the ancient world’s first organized efforts at empirical research.
Inventing Formal Logic
Aristotle’s most lasting intellectual achievement may be his invention of formal logic, the study of what makes an argument valid regardless of its subject matter. His central tool was the syllogism: a structured argument with two premises that share one term in common, leading to a conclusion that necessarily follows. The shared term (which Aristotle called the “middle term”) connects the two ideas in the premises, producing a new statement that must be true if the premises are true.
A classic example: “All humans are mortal; Socrates is a human; therefore Socrates is mortal.” The middle term, “human,” links the other two ideas together. This framework gave thinkers a reliable method for testing whether conclusions actually follow from their starting assumptions. Aristotle’s logical system remained the dominant approach to reasoning in Europe and the Islamic world for roughly two millennia, until modern mathematical logic expanded on it in the 19th century.
The Heart as the Seat of Intelligence
One of Aristotle’s most famous errors was his belief that the heart, not the brain, was the center of sensation, thought, and movement. He stated plainly that “the brain is not responsible for any of the sensations at all” and that “the motions of pleasure and pain, and generally all sensation plainly have their source in the heart.”
This wasn’t a casual guess. Aristotle was well aware that earlier thinkers like Plato and Hippocrates had argued for the brain’s importance, and he systematically tried to refute them. When opponents pointed out that sense organs like the eyes and ears sit near the brain, Aristotle offered alternative explanations: the eyes face forward so we can see where we’re walking, the ears sit on the sides of the head to capture sound from all directions, and some animals hear and smell without having those organs in their heads at all.
He did acknowledge the brain played a role in the body, but only as a cooling system. The heart, being naturally hot, needed the cold brain to regulate its temperature and keep the body in balance. In Aristotle’s model, the heart and brain worked as a unit, but the heart was always the dominant partner. This view influenced medical thinking for centuries before being overturned by later anatomical discoveries.
Pioneering Work in Biology
Where Aristotle truly excelled as an observer was in biology. He dissected animals, classified species, and recorded detailed observations that in some cases weren’t matched until the invention of the microscope. One notable example is his study of chick embryos. By opening fertilized chicken eggs at different stages, he documented the order in which structures appeared: the heart formed first, then the rest of the internal organs, and finally the external parts. He also noted that structures at the front of the body developed before those at the back.
His embryological theories extended to human reproduction and sparked centuries of debate. Aristotle argued that the male parent contributed the form and animating principle to offspring, while the female contributed only the raw material. The physician Galen, writing several centuries later, strongly disagreed, and the tension between Aristotelian and Galenist views on reproduction became a major intellectual battleground in medieval European universities. Thirteenth-century scholars like Thomas Aquinas sided with Aristotle’s model, while others drew on Galen to argue for a more active female biological role. These debates weren’t purely academic: they influenced medieval theology, including arguments about the nature of the Virgin Mary’s role in the birth of Christ.
How Much of His Work Survives
Only a fraction of Aristotle’s original writings exist today. The modern collection of his works, standardized by a German scholar named Immanuel Bekker in 1831, contains about 45 treatises. But in the centuries after his death, the known body of Aristotelian writing was much larger. It included published dialogues written for general audiences (similar in style to Plato’s), massive data collections assembled by his school, works discussing and critiquing other philosophers, and specialized scientific texts on narrow topics. All of these have been lost.
What survives are largely lecture notes and internal school documents, texts that were never polished for public consumption. This explains why Aristotle’s writing can feel dense and telegraphic compared to Plato’s elegant dialogues. The works we have were likely meant as reference materials for students and colleagues, not as finished books. Despite their rough form, these surviving texts cover an extraordinary range: logic, physics, metaphysics, ethics, politics, rhetoric, poetry, biology, meteorology, and psychology, among others.
Why Aristotle Still Matters
Aristotle’s influence is difficult to overstate. His logical system provided the foundation for rigorous argument across every field. His biological observations launched the tradition of empirical science. His ethical writings, particularly the idea that a good life comes from cultivating virtuous habits rather than following rigid rules, remain central to moral philosophy. His political theory introduced concepts like the analysis of different government types that shaped democratic thinking centuries later.
He was also wrong about many things, from the role of the brain to the mechanics of falling objects to the supposed inferiority of women. But the method he championed, careful observation combined with systematic reasoning, gave later thinkers the tools to correct his own mistakes. That may be his most important legacy: not a set of answers, but a way of asking questions.