The First Philosophers

Thales of Miletus (c. 640-546 b. c.e.) was the first known philosopher. He came up with the theory that water is the essence of life and reality-ignoring for the first time the idea that the gods might have something to do with reality, too. Thus he is credited with originating the field of physical science. Anaximander (c. 610-546 b. c.e.) followed Thales, possibly as his student, but disagreed with Thales’ water theory, suggesting that the substance of the universe and the life in it is unidentifiable. He also said our world is but one of many. Anaximander was followed by his student, Anaximenes (c. 590-525 b. c.e.), who defined his teacher’s unidentifiable substance as air-an idea he based on observing the evaporation of water, or water “changing into air.” Even the human soul consists of air, Anaximenes said. These three men from Miletus, though their theories might sound overly simple today, were quite revolutionary in suggesting that human beings can use their own reasoning and observations to come up with the definition of life itself.

Another great thinker from Ionia was Pythagoras, though his greatest fame came from work he did after he left his homeland. He believed the universe could be explained through mathematics and taught that souls were immortal and entered new bodies after people died, and that a person’s actions in life influenced what kind of body his or her soul would later next. He also developed what seems today like a cult. A group of

Students, both men and women, lived with him apart from Greek society. The Pythagoreans were vegetarians and avoided the usual Greek religious rites.

The Pythagorean Theorum

Pythagoras and his followers also did important work in mathematics, and Pythagoras is best known today for the theorem that bears his name. Students around the world learn that the sum of the squares of the length of each side of a right triangle equals the square of the length of the hypotenuse: a2 + b2 = c2. With this formula, a person can determine the length of any side of a right triangle if he or she knows the length of the other two sides.

The Ionians were followed in the fifth century B. C.E. by other philosopher-scientists who continued to challenge their predecessors’ ideas about the universe and the nature of reality. Parmenides (b. 510 B. C.E.) was significant for suggesting that the input from human senses should be put aside in favor of reasoning to answer questions about the universe, which he considered to be an unchanging, fixed entity, despite what our senses might tell us. His challenge, then, to future philosophers was to use intellectual methods to support their notions of reality, as well as their observations. Another Ionian, Pericles’ friend Anaxagorus (c. 500-428 B. C.E.), said change is inevitable because of minute particles that are always in constant flux. These particles, or seeds, made up everything that existed, forming different combinations to create such diverse things as a person and a dog. His arguments were expanded on by other philosophers, who said the small particles could not be divided into smaller particles, and were in constant motion. In Greek, these particles were called a-toma, or “uncuttable,” which led to the English words atom and atomic. Modern science has shown that the Greek atomists were right about the idea of indivisible particles that comprise all matter in the universe.