In 585 B.C.E., Thales of Miletus, through his work in the prediction of an eclipse of the sun, marked the traditional beginning of Western thought in Ancient Greece. Little is known of the early work of Thales, but he is typically recognized as the first of the Presocratic Greek Philosophers. These thinkers are traditionally known as the group of men who lived and worked in Greece, Ionia, and Italy before and during the life of Socrates (470 - 399).

It was not simply Thales' astronomical prediction that made him so recognized, after all, the Babylonians and Egyptians had astronomies that were far more advanced. Thales and his contemporaries were the first to break with such purely scientific research and to seek to commit to argument and critical inquiry, as well as the nature of justification. Also, they were some of the first thinkers to seek an explanation of the natural world that did not appeal to terms outside of the natural world.

Timeline of the Presocratics

 BCE   625   600   575   550   525   500   475   450   425   400   375   350   325
                                            |?   Melissus    |
                                      |    Anaxagoras   |
                              | Heraclitus |
                     |       Xenophanes       |
              |?     Anaximenes      |
           |  Anaximander  |
Ionia  |      Thales     |
                                                                 |    Aristotle   |
                                                         |     Plato     |
                                                |  Critias  |
                                               |      Democritus     |
Greece                                        |  Diogenes of Apollonia  |

                                               |?    Leucippus      |
                                               |   Socrates    |
                                            |   Antiphon    |
                                          |        Gorgias       |                                      
                                          |   Protagoras  |

                                              |   Philolaus     |
                                         |    Zeno     |
Italy                                   |  Empedocles  |
                                  |    Parmenides    |
                     | Pythagoras of Samos |

 BCE   625   600   575   550   525   500   475   450   425   400   375   350   325

Knowledge of presocratic thought is limited. None of their original works have survived, therefore what is known of their work and ideas comes from quotations and summaries in other works. The most important of these sources are, as might be guessed, Plato and Aristotle's works. Also vital to understanding the presocratics is the work of Neoplatonist philosopher Simplicius, who wrote in the sixth century A.D.

The Presocratic philosophers are often divided up in the following manner:

  • The Milesians: These three philosophers were all from the city of Miletus in Ionia. They are also sometimes known as the Milesian school. It has been stated that Thales was Anaximander's teacher, and Anaximander then taught Anaximenes. All of them held that the universe began as a single material substance that changed somehow to give the universe at it now exists. This view is also known as material monism. It was also their belief that this one material was underlying in everything in the universe, constituting the basic nature of everything in it. This material also contains its own source of change and movement.
  • The Pythagoreans: Pythagoras was known for his community that he founded in southern Italy, in the town of Croton. This school was political, religious, and philosophical in nature. After being in Croton for twenty years, there was a revolt against the influence of Pythagoras' school in the town and elsewhere in Italy. Because of this, many of his followers were driven out. During this period, the school split, into the mathematikoi and the akousmatikoi. The former group studied philosophy, mathematics, music, and astronomy, while the latter group followed Pythagoras' teachings on religion and moral living. Pythagoreans believed that numbers were the key to understanding the universe. Indeed, one of their most fascinating insights was that numerical ratios on musical scales indicated that the supposed chaotic nature of sound could be made rational and understandable, and therefore the entire universe is a harmonious arrangement ordered by number.
  • Xenophanes
  • Heraclitus
  • Parmenides
  • The Pluralists: Perhaps the most central problem facing the pluralists of the presocratic era was the rejection of "change" by Parmenides. He described the Doxa, which is a cosmological account of the universe that is deceptive. He thought that "genuine being" was that which was whole, unchanging, and complete on its own. Pluralists, however, sought to justify the changing world of sensory experience in light of the insights offered by Parmenides. They claimed that the basic substances of the universe are the objects which have the "genuine being" that he was thinking of. And while these substances are unchanging, they can be mixed with other things to other, different, changing substances.
  • Zeno
  • The Atomists: The atomists thought that there were an infinite number of atoms, each of which was unchangeable (reflecting back to Parmenidean thought). Atoms differ between one another in shape and size only. These atoms moved in a 'void,' which should not be taken to be a negation of what is; the Greek word best translates as "empty." They postulated that these atoms would never actually touch, they just came very close to one another. The various changes of coming together and separating is what forms the basis for all change in the natural world.
  • Melissus
  • Diogenes
  • The Sophists: In the main, the presocratics concerned themselves with natural philosophy, formulating theories about the nature of the world. However, the sophist movement was one of social, moral, and political thought. Specifically, they examined the problem of whether morality was a matter of nature or convention. Rhetoric was their primary art, giving orations to huge crowds of people and travelling all around the Ancient Greek world. In one sense, they were popular with many and considered quite fascinating. Others, mainly opposing factions in politics, considered them dangerous. Socrates considered them rather dim. They took in large fortunes for their troubles, and had a sizeable following.

The most important thing about the presocratics is their influence; Western thought would be based on their work for hundreds of years. Many of their arguments sound ridiculous and strange today, but when examining the particulars of their arguments an interesting evolution can be seen. Their work would be the foundation for the philosophical projects taken on by Plato and Aristotle, and thus their influence stretched for generations beyond their deaths.


A Presocratics Reader. Ed. Patricia Curd. Tr. Richard D. McKirahan, Jr.

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