(384-322 B.C.)

Aristotle is commonly regarded as one of the greatest thinkers of ancient times. He was deeply interested in philosophy and the physical world. He observed the behavior of animals and examined the structures of living things. Aristotle classified living things according to their traits, rather than their usefulness to humans.

Aristotle's impact on the modern world is apparent in many words in modern languages that can be traced to his writings. Terms of grammar such a subject and predicate come from Aristotle as well as words used to describe basic scientific principles like matter, energy, potential, cause, genus, and species.

Aristotle was the son of a physician who worked for the king of Macedonia. When Aristotle was 18, he entered Plato's school at Athens, the Academy. He stayed there for about 20 years then joined a group called Plato's disciples for 3 years. When he was 41, he went to the court of King Philip II of Macedonia to attend to the education of his son, Alexander (who later became Alexander the Great).

When Alexander came of age, Aristotle returned to Athens and founded his own school, the Lyceum. The Lyceum used the peripatetic teaching method, which is Greek for walking about. Aristotle taught while walking with his students. In 323 B.C. Aristotle fled a group called the Athenians who charged him with impiety, to the city of Chalcis and died there a year after. Few of Aristotle's works survive today but their existence is documented in references by other writers in ancient times.