Beginning in eighteenth-century historiography,[1] many came to regard him as the first philosopher in the Greek tradition, breaking from the prior use of mythology to explain the world and instead using natural philosophy.

[2] Thales' view that all of nature is based on the existence of a single ultimate substance, which he theorized to be water, was widely influential among the philosophers of his time.

"[3] The main source concerning the details of Thales's life and career is the doxographer Diogenes Laërtius, in his third-century-AD work Lives and Opinions of the Eminent Philosophers.

[28] Aside from Egypt, the other mathematically advanced, ancient civilization before the Greeks was Babylonia, another commonplace attribution of travel for a mathematically-minded philosopher.

Van der Waerden come down on the side of Babylonian mathematics influencing the Greeks, citing the use of e. g. the sexagesimal system (or base 60).

According to the 10th-century Byzantine encyclopedia the Suda, the proverb is both "applied to those whose boasts exceed what they are" and "a warning to pay no attention to the opinion of the multitude.

In one version (that Laërtius credits to Callimachus in his Iambics) Bathycles of Arcadia states in his will that an expensive bowl "'should be given to him who had done most good by his wisdom.'

'"[41] According to Diogenes Laërtius, Thales gained fame as a counselor when he advised the Milesians not to engage in a symmachia, a "fighting together", with the Lydians.

[citation needed] Early Greeks, and other civilizations before them, often invoked idiosyncratic explanations of natural phenomena with reference to the will of anthropomorphic gods and heroes.

[45] In the work, Aristotle reported Thales's theory that the arche or originating principle of nature was a single material substance: water.

Writing centuries later, Diogenes Laërtius also states that Thales taught "Water constituted (ὑπεστήσατο, 'stood under') the principle of all things.

"[48][f] According to Aristotle:[45] That from which is everything that exists and from which it first becomes and into which it is rendered at last, its substance remaining under it, but transforming in qualities, that they say is the element and principle of things that are.

[58] According to one author, while visiting Egypt,[25] Thales observed that when the Egyptians drew two intersecting lines, they would measure the vertical angles to make sure that they were equal.

[60] Due to the variations among testimonies, such as the story of the ox sacrifice being accredited to Pythagoras upon discovery of the Pythagorean theorem rather than Thales, some historians (such as D. R. Dicks) question whether such anecdotes have any historical worth whatsoever.

[69] Thales was also a noted astronomer, acknowledged in antiquity for describing the position of Ursa Minor, and he thought the constellation might be useful as a guide for navigation at sea.

[71] Thales thought the Earth must be a flat disk or mound of land and dirt which is floating in an expanse of water.

[72] Heraclitus Homericus states that Thales drew his conclusion from seeing moist substance turn into air, slime and earth.

It seems likely that Thales viewed the land as coming from the water on which it floated and the oceans that surround it, perhaps inspired by observing silt deposits.

[77] According to Seneca, Thales explained the flooding of the Nile as due to the river being beaten back by the etesian wind.

Another version of the story has Aristotle explain that Thales had reserved presses in advance, at a discount, and could rent them out at a high price when demand peaked, following his prediction of a particularly good harvest.

American writer Isaac Asimov described this battle as the earliest historical event whose date is known with precision to the day, and called the prediction "the birth of science".

[83] Afterwards, on the refusal of Alyattes to give up his suppliants when Cyaxares sent to demand them of him, war broke out between the Lydians and the Medes, and continued for five years, with various success.

As, however, the balance had not inclined in favour of either nation, another combat took place in the sixth year, in the course of which, just as the battle was growing warm, day was on a sudden changed into night.

[43]However, based on the list of Median kings and the duration of their reign reported elsewhere by Herodotus, Cyaxares died 10 years before the eclipse.

[86][87][l] "Thales was studying the stars and gazing into the sky, when he fell into a well, and a jolly and witty Thracian servant girl made fun of him, saying that he was crazy to know about what was up in the heavens while he could not see what was in front of him beneath his feet.

[91] While Herodotus reported that most of his fellow Greeks believe that Thales did divert the river Halys to assist King Croesus' military endeavors, he himself finds it doubtful.

[92] According to Aristotle, Thales thought "all things are full of gods",[10][93] i. e. lodestones had souls, because iron is attracted to them (by the force of magnetism).

For evidence, he points to the fact that hydor meant specifically "fresh water", and also that Acheloios was seen as a shape-shifter in myth and art, so able to become anything.

He also points out that the rivers of the world were seen as the "sinews of Acheloios" in antiquity, and this multiplicity of deities is reflected in Thales's idea that "all things are full of gods.

"[99] Diogenes Laërtius quotes Apollodorus as saying that Thales died at the age of 78 during the 58th Olympiad (548–545 BC) and attributes his death to heat stroke and thirst while watching the games.