384-322 B.C.

Greek philosopher and scientist

Aristotle was one of the great philosophers* of ancient Greece. He was interested in an extraordinary number of subjects and he wrote important works on many of them. He created methods of philosophical study that are still used. He also conducted systematic research in such fields as animal anatomy and Greek political systems. His written works covered these subjects as well as psychology, astronomy, physics, and literature. His work had an enormous influence on later generations of scholars through the Middle Ages to modern times.

* philosopher scholar or thinker concerned with the study of ideas, including science

* dialogue text presenting an exchange of ideas between people

Aristotle the Teacher. Aristotle was born in Stagira in Macedonia in northern Greece. His father was a doctor and court physician to Macedonia’s King Amyntas II. Aristotle’s interest in animal studies and his knowledge of dissection may have been influenced by his father’s profession.

At the age of 17, Aristotle traveled to Athens and entered Plato’s Academy. Plato was an important Greek philosopher whose writings shaped the development of Western thought, and the Academy was a school for philosophers that Plato founded. Aristotle remained there as a student and associate for 20 years. During this time, he wrote several dialogues* that became famous in the ancient world. Only fragments of these works have survived.

When Plato died in 347 B.C., Aristotle left Athens for northern Asia Minor. There he met Pythias, the woman who became his wife. He also began his biological research, studying marine species in the Aegean Sea off the island of Lesbos. In 342 B.C., he returned to Macedonia to become tutor to the 13-year-old son of King Philip II. That son later became Alexander the Great, the Greek conqueror who brought all of Persia as well as parts of India under his control.

As Alexander’s teacher, Aristotle wrote several other works that have not survived, including Monarchy. It would be interesting to know what advice he gave to Alexander on this subject. But when discussing monarchs in his later work, Politics, he notably omitted mention of Alexander as a worthy example. He also did not stay with Alexander’s court beyond his teaching appointment.

Soon after Philip died, Aristotle returned to Athens and founded his own school—the Lyceum—where he taught for 12 years. Then, in 323 B.C., Alexander the Great died, and there was a wave of anti-Macedonian feeling in Athens. Apparently fearing for his life, Aristotle returned to Macedonia, where he died a year later of a stomach ailment.

Aristotle's Works. Nearly all of Aristotle’s surviving works date from his years at the Lyceum. They seem to be lecture notes that he developed for teaching there, and they were kept at the Lyceum when he left for Macedonia. The notes then changed hands several times over the next two hundred years. It was not until the first century B.C. that various editors organized the works in the form known today.

Aristotle’s works fall into groups of texts on related subjects. In his works on logic*, which include Categories, On Interpretation, Prior Analytics, and Posterior Analytics, he discussed the process of reasoning and constructing valid arguments. In Metaphysics, he drew a distinction between matter (the material substance of objects in the world) and form (the special nature of an object that gives it an identity).

Aristotle wrote several works on the natural sciences, including Physics, which considers such subjects as time, space, movement, and change in nature. On the Heavens sets forth his views on astronomy. In a series of works, including On the Soul, he discussed various aspects of human psychology. He also wrote texts on weather and on the biology of animals.

In two of his works on ethics*, Nichomachean Ethics and Eudemian Ethics, Aristotle wrote about morality and human behavior. He considered human society in a wider context in Politics, where he discussed citizenship and systems of government, such as democracy and monarchy. He also produced works on art, including Rhetoric, which is about persuasive public speaking, and Poetics, which concerns poetry and drama.

* logic principles of reasoning

* ethics branch of philosophy that deals with moral conduct, duty, and judgment

* construct working hypothesis or concept

Aristotle was one of the greatest and most important philosophers in history. A student of Plato and tutor to Alexander the Great, Aristotle studied a wide range of subjects. His works in such fields as logic and political theory remained influential through the Middle Ages and into the modern age.

Aristotle's Method. Aristotle was not a scientist in the modern sense. Although his studies of animals involved much firsthand observation, he did not base his work solely on observed facts. For his work in philosophy, he used human beliefs and interpretations—both his own and those of other people—as raw material.

Typically, Aristotle’s lectures would start with a careful and respectful review of other people’s opinions about a topic. Then he would investigate and compare these opinions, exploring where they differed and how parts of them might fit together. One of his strengths as a thinker was his ability to approach questions from many different directions. Finally, he would try to develop a logical and consistent view, rejecting some ideas but saving as many as he could. The result would be a construct* of ideas that Aristotle called “scientific understanding.” This technique led him to break new ground in many subjects.

His thoughts about matter and form provide an example of this method. One of the issues that philosophers have always discussed is the nature of objects and events. What makes one object a chair and another a person? How much do they have to change before they cease to be a chair or a person? How do we know when that has happened? The answers at first seem obvious, but careful thought shows that they are based on complicated assumptions.

When Aristotle wrote, there were two schools of thought about matter and form. The earliest Greek philosophers focused on the materials of which objects were made and the ways in which the materials changed. Aristotle argued that this was not enough—changes could occur even if the materials remained identical. For example, when an animal dies it becomes a heap of matter that is no longer an animal, even though it consists of the same materials. Similarly, if a chair is pulled apart and made into something else, the materials are the same, but the object has changed. Thus, the identity of an animal or a chair is not defined by its materials alone.


Aristotle's work influenced the thinking of writers, philosophers, and scientists for many centuries after his death. His ideas became particularly important during the Middle Ages. In the A.D. 800s, his works were translated into Arabic and studied by Islamic and Jewish scholars. Latin translations made in the 1100s and 1200s launched a surge of interest in Aristotle in the West, enabling Christian theologians, such as Thomas Aquinas, to use Aristotle’s ideas about the human soul. In the 1620s, the philosopher Francis Bacon was influenced by Aristotle. Even later, in the 1800s, the naturalist Charles Darwin expressed his admiration for Aristotle's work in biology.

* syllogism form of argument in which two true statements (premises) lead to a third statement (conclusion) that must also be true

The other school of thought was that of Aristotle’s teacher Plato. Plato’s solution to the problem was that there must be something nonmaterial about an animal, a chair, or indeed a human being. Plato called this a form, something that incorporates all the properties of an object but exists on an ideal plane. He argued that forms were in fact more real than objects, and objects appeared only when forms were in some way projected onto matter.

Aristotle did not fully agree with Plato’s theory of forms. He accepted that the idea of form was needed for identifying an object. But he saw no reason to conclude that forms had a reality apart from their existence in objects. Further, he noted that some properties of a particular form were unimportant for identifying an object, while others were vital. For example, a person who becomes tanned by the sun remains the same person, but a statue, however lifelike, never becomes the person it represents. Continuing this line of argument, Aristotle developed ideas on how we perceive and think that are still relevant and are similar to some theories of modern psychology.

Logic. Aristotle’s most important contribution to human thought is often said to be his analysis of formal logic, described in his text Prior Analytics. Formal logic shows how arguments can be presented in syllogisms*, built from premises. Premises are basic understandings that lead to conclusions. The conclusions, in turn, become the premises for other conclusions. This analysis has never been improved.

Of course, Aristotle’s answers were not always accurate. A very influential argument that is now known to be false is his theory of four elements. He argued that all materials are made up of one or more of the following elements—fire, air, water, or earth. As might be expected, he gave logical explanations for this idea, but the premises, or basic principles on which his argument rested, were incorrect.

Good Living. For all Aristotle’s focus on logic, however, his thinking was not rigid. He accepted that some subjects, such as politics and ethics, are practical matters that are by nature inexact.

In Nichomachean Ethics, Aristotle tried to explore what is really meant by “good living.” He concluded that good living cannot be defined by a logical system that always works out. Instead, the real world creates situations where different values sometimes come into conflict. He saw rules for behavior as only summaries of the practical wisdom of others. In an effort to live a good life, individuals must apply careful reasoning and develop their own judgment. Aristotle’s philosophy recognizes these complexities of human life, even while it strives for order and reason. (See also Philosophy, Greek and Hellenistic; Science.)

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