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"Thales of Miletus", in Wikipedia.
https://en.wikipedia.org/wiki/Thales

Thales of Miletus (c. 624 – c. 546 BC) was a pre-Socratic Greek philosopher and mathematician from Miletus in Asia Minor and one of the Seven Sages of Greece. Many, most notably Aristotle, regard him as the first philosopher in the Greek tradition. Aristotle reported Thales’ hypothesis that the originating principle of nature and the nature of matter was a single material substance: water.

Thales attempted to explain natural phenomena without reference to mythology. Almost all of the other Pre-Socratic philosophers follow him in attempting to provide an explanation of ultimate substance, change, and the existence of the world without reference to mythology.

In mathematics, Thales used geometry to calculate the heights of pyramids and the distance of ships from the shore. He is the first known individual to use deductive reasoning applied to geometry, by deriving four corollaries to Thales’ Theorem. He is the first known individual to whom a mathematical discovery has been attributed.

The current historical consensus is that Thales was born in the city of Miletus around the mid 620s BC. Miletus was an ancient Greek Ionian city on the western coast of Asia Minor (in what is today Aydin Province of Turkey), near the mouth of the Maeander River.

The dates of Thales’ life are not exactly known but are roughly established by a few datable events mentioned in the sources. According to Herodotus (and as determined by modern methods), Thales predicted the solar eclipse of May 28, 585 BC. Diogenes Laërtius quotes the chronicle of Apollodorus of Athens as saying that Thales died at the age of 78 during the 58th Olympiad (548–545 BC) and attributes his death to heat stroke while watching the games.

Thales involved himself in many activities, taking the role of an innovator. Some say that he left no writings, others say that he wrote On the Solstice and On the Equinox. (No writing attributed to him has survived.) Diogenes Laërtius quotes two letters from Thales: one to Pherecydes of Syros offering to review his book on religion, and one to Solon, offering to keep him company on his sojourn from Athens. Thales identifies the Milesians as Athenian colonists.

Several anecdotes suggest that Thales was not solely a thinker but was also involved in business and politics. One story recounts that he bought all the olive presses in Miletus after predicting the weather and a good harvest for a particular year. In another version of the same story, Aristotle explains that Thales reserved presses ahead of time at a discount only to rent them out at a high price when demand peaked, following his predictions of a particularly good harvest. This first version of the story would constitute the first creation and use of futures, whereas the second version would be the first creation and use of options. Aristotle explains that Thales’ objective in doing this was not to enrich himself but to prove to his fellow Milesians that philosophy could be useful, contrary to what they thought.

The Greeks often invoked idiosyncratic explanations of natural phenomena with reference to the will of anthropomorphic gods and heroes. Instead, Thales aimed to explain natural phenomena via rational hypotheses that referenced natural processes themselves. For example, rather than assuming that earthquakes were the result of supernatural whims Thales explained them by hypothesizing that the Earth floats on water and that earthquakes occur when the Earth is rocked by waves.

Due to the scarcity of sources concerning Thales and the diversity among the ones we possess, there is a scholarly debate over possible influences on Thales and the Greek mathematicians that came after him.

Historian Roger L. Cooke points out that Proclus does not make any mention of Mesopotamian influence on Thales or Greek geometry, but “is shown clearly in Greek astronomy, in the use of sexagesimal system of measuring angles and in Ptolemy’s explicit use of Mesopotamian astronomical observations.” Cooke notes that it may possibly also appear in the second book of Euclid’s Elements, “which contains geometric constructions equivalent to certain algebraic relations that are frequently encountered in the cuneiform tablets.” Cooke notes “This relation however, is controversial.”

Historian B.L. Van der Waerden is among those advocating the idea of Mesopotamian influence, writing “It follows that we have to abandon the traditional belief that the oldest Greek mathematicians discovered geometry entirely by themselves…a belief that was tenable only as long as nothing was known about Babylonian mathematics. This in no way diminishes the stature of Thales; on the contrary, his genius receives only now the honour that is due to it, the honour of having developed a logical structure for geometry, of having introduced proof into geometry.”

Herodotus wrote that the Greeks learnt the practice of dividing the day into 12 parts, about the polos, and the gnomon from the Babylonians. (The exact meaning of his use of the word polos is unknown, current theories include: “the heavenly dome”, “the tip of the axis of the celestial sphere”, or a spherical concave sundial.)

Dicks points out that the primitive state of Greek mathematics and astronomical ideas exhibited by the peculiar notions of Thales’ successors (such as Anaximander, Anaximenes, Xenophanes, and Heraclitus), which historian J. L. Heiberg calls “a mixture of brilliant intuition and childlike analogies”, argues against the assertions from writers in late antiquity that Thales discovered and taught advanced concepts in these fields.

Thales had a profound influence on other Greek thinkers and therefore on Western history. Some believe Anaximander was a pupil of Thales. Early sources report that one of Anaximander’s more famous pupils, Pythagoras, visited Thales as a young man, and that Thales advised him to travel to Egypt to further his philosophical and mathematical studies.

Many philosophers followed Thales’ lead in searching for explanations in nature rather than in the supernatural; others returned to supernatural explanations, but couched them in the language of philosophy rather than of myth or of religion.

Looking specifically at Thales’ influence during the pre-Socratic era, it is clear that he stood out as one of the first thinkers who thought more in the way of logos than mythos. The difference between these two more profound ways of seeing the world is that mythos is concentrated around the stories of holy origin, while logos is concentrated around the argumentation.

Sources:

Burnet, John (1957) [1892]. Early Greek Philosophy. The Meridian Library. Third Edition
Diogenes Laërtius, Life of Thales, translated by Robert Drew Hicks (1925).
Herodotus, Histories, A. D. Godley (translator), Cambridge: Harvard University Press, 1920.
Hans Joachim Störig, Kleine Weltgeschichte der Philosophie. Fischer, Frankfurt/M. 2004.
Kirk, G.S.; Raven, J. E. (1957). The Presocratic Philosophers. Cambridge: University Press.
G. E. R. Lloyd. Early Greek Science: Thales to Aristotle.
Nahm, Milton C. (1962) [1934]. Selections from Early Greek Philosophy. Appleton-Century-Crofts.
Pliny the Elder, The Natural History (eds. John Bostock, M.D., F.R.S. H.T. Riley, Esq., B.A.) London. Taylor and Francis. (1855).

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