{{Short description|Ancient Greek philosopher (c. 626 – c. 545 BC)}}
{{redirect|Thales|the company|Thales Group|other uses|Thales (disambiguation)}}
{{Use dmy dates|date=May 2025}}
{{Infobox philosopher
| name = Thales of Miletus
| image = Arte romana, testa di talete di mileto, II sec..JPG
| caption =
| birth_date = {{circa}} 626/623 BC
| birth_place = [[Miletus]], [[Ionian League]]
| death_date = {{circa}} 548/545 BC (aged {{circa}} 78) 
| era = [[Pre-Socratic philosophy]]
| region = [[Western philosophy]]
| school_tradition = [[Ionian School (philosophy)|Ionian]]/[[Milesian school|Milesian]]
| main_interests = {{hlist |[[Metaphysics]] |[[mathematics]] |[[astronomy]]}}
| notable_ideas = {{ublist|class=nowrap |[[Philosophy|Philosophical inquiry]]|Water is the ''[[arche]]'' |[[Eclipse of Thales]]|[[Thales's theorem]] |[[Intercept theorem]] |[[Know thyself]]|[[Static electricity]]}}
}}

'''Thales of Miletus''' ({{IPAc-en|ˈ|θ|eɪ|l|iː|z}} {{respell|THAY|leez}}; {{langx|grc|Θαλῆς}}; {{circa|626/623 |548/545 BC|lk=on}}) was a [[Pre-Socratic philosophy|pre-Socratic]] [[Greek philosopher]] from [[Miletus]] in [[Ionia]], [[Asia Minor]]. Thales was one of the [[Seven Sages of Greece|Seven Sages]], founding figures of [[Ancient Greece]].

Beginning in eighteenth-century historiography,{{Sfn|Cantor|2022}} many came to regard him as the first philosopher in the [[Greek philosophy|Greek tradition]], breaking from the prior use of [[mythology]] to explain the world and instead using [[natural philosophy]]. He is thus otherwise referred to as the first to have engaged in [[mathematics]], [[History of science#Pre-socratics|science]], and [[deductive reasoning]].<ref name=Russell>{{Cite book |title=A History of Western Philosophy |last=Russell |first=Bertrand |author-link=Bertrand Russell |year=1945 |publisher= Simon & Schuster }}</ref>

Thales's view that all of [[nature]] is based on the existence of a [[Arche|single ultimate substance]], which he [[Theory|theorized]] to be [[Water (classical element)|water]], was widely influential among the philosophers of his time. Thales thought the Earth floated on water.

In mathematics, Thales is the namesake of [[Thales's theorem]], and the [[intercept theorem]] can also be referred to as Thales's theorem. Thales was said to have calculated the heights of the [[Egyptian pyramids|pyramids]] and the distance of ships from the shore. In science, Thales was an astronomer who reportedly [[Weather forecasting#Ancient forecasting|predicted the weather]] and a [[solar eclipse]]. The discovery of the position of the constellation [[Ursa Major]] is also attributed to Thales, as well as the timings of the [[solstices]] and [[equinoxes]]. He was also an [[engineer]], known for having allowed the [[Lydia]]n army to cross the [[Kızılırmak River|Halys River]]. [[Plutarch]] wrote that "at that time, Thales alone had raised philosophy from mere speculation to practice."<ref>{{cite book| last=Dunham| first=William| title=Journey Through Genius: The Great Theorems of Mathematics| page=6}}</ref>

==Life==
[[File:MiletusIonicStoa.jpg|thumb|right|The Ionic Stoa on the Sacred Way in [[Miletus]].]]

The main source concerning the details of Thales's life and career is the [[Doxography|doxographer]] [[Diogenes Laërtius]], in his third-century-AD work ''[[Lives and Opinions of Eminent Philosophers|Lives and Opinions of the Eminent Philosophers]]''.<ref>Translation of his biography on Thales: [http://www.classicpersuasion.org/pw/diogenes/dlthales.htm Thales] {{Webarchive|url=https://web.archive.org/web/20080209023538/http://classicpersuasion.org/pw/diogenes/dlthales.htm|date=9 February 2008}}, classicpersuasion site; original Greek text, under [https://www.mikrosapoplous.gr/dl/dl01.html#thales ΘΑΛΗΣ], the Library of Ancient Texts Online site.</ref> While it is all we have, Diogenes wrote some eight centuries after Thales's death and his sources often contained "unreliable or even fabricated information".<ref>See {{Cite book |last=McKirahan |first=Richard D. Jr. |url=https://archive.org/details/philosophybefore00mcki/page/5 |title=Philosophy Before Socrates |publisher=Hackett |year=1994 |isbn=978-0-87220-176-7 |location=Indianapolis |page=[https://archive.org/details/philosophybefore00mcki/page/5 5]}}</ref>{{efn|This use of hearsay and a lack of citing original sources leads some historians, like Dicks and Werner Jaeger, to view the whole idea of pre-Socratic philosophy as a construct from a later age, "fashioned during the two or three generations from Plato to the immediate pupils of Aristotle".<ref>{{cite book |last=Jaeger |first=Werner |title=Aristotle |year=1948 |edition=2nd |page=454}}</ref>}} It is known Thales was from [[Miletus]], a mercantile city settled at the mouth of the [[Büyük Menderes River|Maeander River]], near modern [[Didim]], Turkey.

The dates of Thales's life are not exactly known, but are roughly established by a few datable events mentioned in the sources. According to the historian [[Herodotus]], writing in the 5th century BC, Thales [[#Prediction of solar eclipse|predicted a solar eclipse]] in 585 BC.<ref name="1.74.2">Herodotus, [https://www.perseus.tufts.edu/cgi-bin/ptext?lookup=Hdt.+1.74.1 1.74.2], and A. D. Godley's footnote 1; Pliny, [https://www.perseus.tufts.edu/cgi-bin/ptext?lookup=Plin.+Nat.+2.9 2.9 (12)] and Bostock's footnote 2.</ref>  Assuming one's [[wikt:acme#English|acme]] (or [[wikt:floruit#English|floruit]]) occurred at the age of 40, the chronicle of [[Apollodorus of Athens]], written during the 2nd century BC, therefore placed Thales's birth about the year 625 BC.<ref name="Cohenetal">{{cite book |last1=Cohen |first1=Mark S. |url=https://books.google.com/books?id=pFEII68kmVsC |title=Readings in Ancient Greek Philosophy (Fourth Edition): From Thales to Aristotle |last2=Curd |first2=Patricia |last3=Reeve |first3=C. D. C. |date=2011 |publisher=Hackett Publishing |isbn=978-1603846073 |location=Indianapolis, Indiana |page=10}}</ref><ref name="books.google.com">Frank N. Magill, [https://books.google.com/books?id=_CMl8ziTbKYC&pg=PA1121 ''The Ancient World: Dictionary of World Biography'', Volume 1], Routledge, 2003 {{isbn|1135457395}}</ref>

=== Ancestry and family ===
[[File:Griechischen und phönizischen Kolonien.jpg|thumb|upright=1.5|Map of Phoenician (in yellow) and Greek colonies (in red) between the 8th and 6th centuries BC]]

While the probability is that Thales was as Greek as most Milesians,<ref name="kirk-raven">{{cite book |last1=Kirk |first1=G. S. |title=The Presocratic Philosophers |last2=Raven |first2=J. E. |publisher=Cambridge University Press |year=1957 |pages=74–98 |chapter=Chapter II: Thales of Miletus |chapter-url=https://archive.org/details/presocraticphilo033229mbp/page/74}}</ref> [[Herodotus]] described Thales as "a [[Phoenicia]]n by remote descent".<ref name="Freely2012">{{cite book|url=https://books.google.com/books?id=e4ye9m3EflQC&q=Thales+of+Miletus+Phoenician&pg=PA7|title=The Flame of Miletus: The Birth of Science in Ancient Greece (And How It Changed the World)|last1=Freely|first1=John|date=2012|publisher=I. B. Tauris & Co. Ltd.|isbn=978-1-78076-051-3|location=London|page=7|access-date=1 October 2017}}</ref> Diogenes Laërtius references Herodotus, [[Duris of Samos|Duris]], and [[Democritus]], who all agree "that Thales was the son of Examyas and Cleobulina, and belonged to the Thelidae who are Phoenicians and amongst the noblest descendants of [[Cadmus]] and [[Agenor]]" who had been banished from Phoenicia and that Thales was enrolled as a citizen in Miletus along with [[Neleus (son of Codrus)|Neleus]].<ref name="Russel">{{cite book|last=Lawson|first=Russell M.|date=2004|title=Science in the Ancient World: An Encyclopedia|url=https://books.google.com/books?id=1AY1ALzh9V0C&pg=PA234|location=Santa Barbara, California; Denver, Colorado; and Oxford, England|publisher=ABC CLIO|isbn=978-1-85109-534-6|pages=234–235}}</ref><ref>{{Cite book |last=Thatcher |first=Oliver J. |url=https://books.google.com/books?id=G9-qE_CIIZkC&pg=PA138 |title=The Library Of Original Sources: The Greek World |date=2004 |publisher=The Minerva Group, Inc. |isbn=978-1-4102-1402-7 |pages=138 |language=en}}</ref>

However, [[Friedrich Nietzsche]] and others interpret this quote as meaning only that his ancestors were [[Seamanship|seafaring]] [[Cadmea|Cadmeians]] from [[Boeotia]].<ref name="Nietzsche">{{cite book |last=Nietzsche |first=Friedrich |url=https://books.google.com/books?id=yjaEkWbwBm0C&q=herodotus+1.170+examyes&pg=PA23 |title=The Pre-Platonic Philosophers |year=2001 |isbn=978-0252025594 |page=23|publisher=University of Illinois Press }}</ref><ref name=heroon>Alexander Herda. Burying a sage: the heroon of Thales in the agora of Miletos: With remarks on some other excavated Heroa and on cults and graves of the mythical founders of the city. 2èmes Rencontres d'archéologie de l'IFEA : Le Mort dans la ville Pratiques, contextes et impacts des inhumations intra-muros en Anatolie, du début de l'Age du Bronze à l'époque romaine., Nov 2011, Istanbul, Turkey. pp. 67–122</ref> It is also possible that he was of mixed ancestry, given his father had a [[Carians|Carian]] name and his mother had a Greek name.<ref name="heroon"/><ref name=brit>{{Cite book |last=Yust |first=Walter |url=https://books.google.com/books?id=YUYqAAAAMAAJ |title=Encyclopaedia Britannica: A New Survey of Universal Knowledge |date=1952 |publisher=[[Encyclopaedia Britannica]] |pages=13 |language=en}}</ref><ref>{{Cite book |last=Guthrie |first=W. K. C. |url=https://books.google.com/books?id=ogUR3V9wbbIC&pg=PA50 |title=A History of Greek Philosophy: The Earlier Presocratics and the Pythagoreans |date=1978 |publisher=Cambridge University Press |isbn=978-0-521-29420-1 |volume=1 |page=50 |language=en}}</ref> Diogenes Laërtius seems to also reference an alternative account: "Most writers, however, represent him as a genuine Milesian and of a distinguished family".<ref>{{Cite book |last=Goodman |first=Ellen |url=https://books.google.com/books?id=bB_0M9oviBQC&pg=PA9 |title=The Origins of the Western Legal Tradition: From Thales to the Tudors |date=1995 |publisher=Federation Press |isbn=978-1-86287-181-6 |page=9 |language=en}}</ref>  ''[[Encyclopædia Britannica|Encyclopedia Britannica]]'' (1952) concluded that Thales was most likely a native Milesian of noble birth and that he was certainly a Greek.<ref name=brit/>

Diogenes continues, by delivering more conflicting reports: one that Thales married and either fathered a son (Cybisthus or Cybisthon) or adopted his nephew of the same name; the second that he never married, telling his mother as a young man that it was too early to marry, and as an older man that it was too late.{{efn|In addition, his supposed mother, Cleobulina, has also been described as his companion instead of his mother.<ref name="Plant">{{cite book|last=Plant|first=I. M.|title=Women Writers of Ancient Greece and Rome: An Anthology|year=2004|publisher=University of Oklahoma Press|location=Norman|pages=29–32}}</ref>}} [[Plutarch]] had earlier told this version: [[Solon]] visited Thales and asked him why he remained single; Thales answered that he did not like the idea of having to worry about children. Nevertheless, several years later, anxious for family, he adopted his nephew Cybisthus.<ref>{{cite book |last=Plutarch |title=Lives |year=1952 |publisher=William Benton |location=Chicago |page=66 |chapter=Solon |editor=Robert Maynard Hutchins |series=Great Books of the Western World |volume=14}}</ref>

=== Travels ===
The culture of [[Archaic Greece]] was heavily influenced by those of the [[Levant]] and [[Mesopotamia]].<ref>Riedweg, Christoph (2005) [2002], ''Pythagoras: His Life, Teachings, and Influence'', Ithaca, New York: Cornell University Press, {{ISBN|978-0-8014-7452-1}} p. 7</ref> It is said Thales was engaged in trade and visited either [[Ancient Egypt|Egypt]] or [[Babylonia]].<ref>Plutarch, Life of Solon § 2.4</ref> However, there is no strong evidence that Thales ever visited countries in the [[Near East]], and the issue is disputed among scholars.<ref>{{Cite book |last=O'Grady |first=Patricia F. |url=https://books.google.com/books?id=ZTUlDwAAQBAJ&pg=PA263 |title=Thales of Miletus: The Beginnings of Western Science and Philosophy |year=2017 |publisher=Taylor & Francis |isbn=978-1-351-89537-8 |page=263 |language=en}}</ref> Visits to such places were a commonplace attribution to various philosophers by later writers, especially when these writers tried to explain the origin of their mathematical knowledge, such as with Thales or [[Pythagoras]] or [[Eudoxus of Cnidus|Eudoxus]].<ref>{{Cite book |last=Hamlyn |first=David W. |url=https://books.google.com/books?id=SmqIAgAAQBAJ |title=Being a Philosopher: The History of a Practice |date=2002 |publisher=Routledge |isbn=978-1-134-97101-5 |pages=7 |language=en}}</ref><ref name=Russell />

====Egypt====
[[File:All Gizah Pyramids.jpg|thumb|Thales may have been educated in Egypt.]]

Several ancient authors assume that Thales, at one point in his life, visited [[Egypt]], where he learned about geometry.<ref name="Russo">{{cite book|url=https://books.google.com/books?id=ld8lBAAAQBAJ&q=thales&pg=PA33|isbn=978-3642189043|first=Lucio|last=Russo|translator-first=Silvio|translator-last=Levy|page=33|year=2013|title=The Forgotten Revolution: How Science Was Born in 300 BC and Why it Had to Be Reborn|publisher=Springer }}</ref> It is considered possible that Thales visited Egypt, since Miletus had a permanent colony there (namely [[Naucratis]]). It is also said Thales had close contacts with the priests of [[Thebes, Egypt|Thebes]] who instructed him, or even that he instructed ''them'' in geometry.<ref>{{cite book |last=Harrison |first=Frederic |author-link=Frederic Harrison |url=https://archive.org/details/newcalendargrea03harrgoog/page/n120/mode/2up |title=The new calendar of great men: biographies of the 558 worthies of all ages |publisher=MacMillan & Co |year=1892 |location=London and New York |page=92 }}</ref><ref>Plutarch, ''[https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Plutarch/Moralia/Isis_and_Osiris*/A.html On Isis And Osiris]'', ch. 10.</ref> It is also possible Thales knew about Egypt from accounts of others, without actually visiting it.<ref>{{Cite book|last=Ferguson|first=Kitty|author-link=Kitty Ferguson|url=https://books.google.com/books?id=trM7NJz011oC&pg=PT28|title=Pythagoras: His Lives and the Legacy of a Rational Universe|year=2011|publisher=Icon Books Ltd|isbn=978-1-84831-250-0|pages=28|language=en}}</ref>

====Babylon====
Aside from Egypt, the other mathematically advanced, ancient civilization before the Greeks was Babylonia, another commonplace attribution of travel for a mathematically-minded philosopher.<ref name="Cooke">{{cite book |last=Cooke |first=Roger L. |title=The History of Mathematics: A Brief Course |publisher=John Wiley & Sons, Inc. |year=2005}}</ref>

Historians Roger L. Cooke and [[Bartel Leendert van der Waerden|B.L. Van der Waerden]] come down on the side of Babylonian mathematics influencing the Greeks, citing the use of e. g. the [[sexagesimal system]] (or [[Radix|base]] 60).<ref name="Cooke" /> Cooke notes "This relation, however, is controversial."<ref name="Cooke" /> Other historians, such as D. R. Dicks, take issue with the idea of Babylonian influence on Greek mathematics. For until around the time of [[Hipparchus]] (c. 190–120&nbsp;BC) their sexagesimal system was unknown.<ref name="Dicks" />

Herodotus wrote the Greeks learnt the ''[[gnomon]]'' from the Babylonians. Thales's follower Anaximander is credited with introducing the ''gnomon'' to the Greeks.<ref>Diogenes Laertius (II, 1)</ref> Herodotus also wrote that the practice of dividing the day into 12 parts, and the ''polos'', came to the Greeks from the Babylonians.{{efn|The exact meaning of this 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.<ref>{{Cite web |url=https://penelope.uchicago.edu/Thayer/E/Roman/Texts/secondary/SMIGRA*/Polus.html |title=LacusCurtius • Ancient Astronomy: Polus (Smith's Dictionary, 1875) |website=penelope.uchicago.edu}}</ref>}} Yet this too is disputed, for example by historian L. Zhmud, who points out the ''gnomon'' was known to both Egyptians and Babylonians, the division of the day into twelve parts (and by analogy the year) was known to the Egyptians already in the [[2nd millennium BC]], and the idea of the ''polos'' was not used outside of Greece at this time.<ref>{{cite book |last=Zhmud |first=Leonid |title=The Origin of the History of Science in Classical Antiquity |publisher=Die Deutsche Bibliothek |year=2006}}</ref>

===Sagacity===
[[File:Nuremberg chronicles f 59r 2.png|thumb|upright=0.8|Thales, [[Nuremberg Chronicle]].]]

Thales is recognized as one of the Seven Sages of Greece, semi-legendary wise [[Politician|statesmen]] and founding figures of Ancient Greece. While which seven one chooses may change, the seven has a canonical four which includes Thales, Solon of Athens, [[Pittacus of Mytilene]], and [[Bias of Priene]]. Diogenes Laërtius tells us that the Seven Sages were created in the [[archon]]ship of Damasius at [[Athens]] about 582&nbsp;BC and that Thales was the first sage.<ref>Diogenes Laërtius 1.22</ref>{{efn|The same story, however, asserts that Thales emigrated to Miletus; and that he did not become a student of nature until after his political career. This story has to be rejected if one is to believe that Thales was a native of Miletus, and other typical things about him like his prediction of the eclipse.}}

The sages were associated with the [[Delphic maxims]], a quote or maxim attributed to each one inscribed on the [[Temple of Apollo (Delphi)|Temple of Apollo]] at [[Delphi]]. Thales has arguably the most famous of all, ''gnothi seauton'' or [[know thyself]]. 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."<ref>{{Cite web|url=https://www.cs.uky.edu/~raphael/sol/sol-entries/gamma/334|title=SOL Search|website=www.cs.uky.edu}}</ref>{{efn|The aphorism has also been attributed to various other philosophers. [[Diogenes Laërtius]] attributes it to Thales<ref>''[[Lives and Opinions of Eminent Philosophers|Lives]]'' I.40</ref><ref name="auto1">{{Cite web|url=https://www.cs.uky.edu/~raphael/sol/sol-entries/theta/17|title=SOL Search|website=www.cs.uky.edu}}</ref> but notes that Antisthenes in his ''Successions of Philosophers'' attributes it instead to [[Phemonoe]], a mythical Greek poet. The Roman poet [[Juvenal]] quotes the phrase in Greek and states that the precept descended ''e caelo'' (from heaven).<ref>''[[Satires of Juvenal#Satire XI: Dinner and a Moral|Satires]]'' 11.27</ref> Other names of potential include [[Pythagoras]]<ref>{{Cite book | last1=Vico | first1=Giambattista | last2=Visconti | first2=Gian Galeazzo | title=On humanistic education: (six inaugural orations, 1699–1707) | version=Six Inaugural Orations, 1699–1707 From the Definitive Latin Text, Introduction, and Notes of Gian Galeazzo Visconti | publisher=Cornell University Press | year=1993 | page=[https://archive.org/details/onhumanisticeduc00vico/page/4 4] | url=https://archive.org/details/onhumanisticeduc00vico| url-access=registration | isbn=0801480876 }}</ref> and [[Heraclitus]].<ref>Doctoral thesis, "Know Thyself in Greek and Latin Literature," Eliza G. Wilkens, U. Chi, 1917, p. 12 ([https://archive.org/details/knowthyselfingr00wilkgoog <!-- quote=know thyself xenophon. --> online]).</ref>}}

==== Golden tripod ====
Diogenes Laërtius relates several stories of an expensive, gold tripod or bowl that is to go to the most [[Wisdom#Mythological and philosophical perspectives|wise]]. 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.' So it was given to Thales, went the round of all the sages, and came back to Thales again. And he sent it to [[Didyma|Apollo at Didyma]], with this dedication...'Thales the Milesian, son of Examyas [dedicates this] to Delphinian Apollo after twice winning the prize from all the Greeks.{{'"}}<ref>{{harvnb|Laërtius|1925|loc=§ 28}}</ref>

==== Diplomacy ====
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. This has sometimes been interpreted as an alliance.<ref>[[Diogenes Laërtius]] 1.25</ref>

[[Croesus]] was defeated before the city of [[Sardis]] by [[Cyrus the Great]], who subsequently spared Miletus because it had taken no action. Cyrus was so impressed by Croesus’ wisdom and his connection with the sages that he spared him and took his advice on various matters.{{Citation needed|date=January 2019}} The Ionian cities should be demoi, or "districts".

{{blockquote|He counselled them to establish a single seat of government, and pointed out [[Teos]] as the fittest place for it; "for that," he said, "was the centre of [[Ionia]]. Their other cities might still continue to enjoy their own laws, just as if they were independent states."<ref name=Rawlinson/>}}

Miletus, however, received favorable terms from Cyrus. The others remained in an Ionian League of twelve cities (excluding Miletus), and were subjugated by the Persians.{{Citation needed|date=January 2019}}

== Theories and studies ==

Early Greeks, and other civilizations before them, often invoked [[idiosyncratic]] explanations of natural phenomena with reference to the will of [[Anthropomorphism|anthropomorphic]] [[Deity|gods]] and [[hero]]es. Instead, Thales aimed to explain natural phenomena via rational hypotheses that referenced natural processes themselves—<ref name="O'Grady2017">{{cite book |last=O'Grady |first=Patricia F. |url=https://books.google.com/books?id=fElBDgAAQBAJ&pg=PT102 |title=Thales of Miletus: The Beginnings of Western Science and Philosophy |year=2017 |publisher=Taylor & Francis |isbn=978-1-351-89536-1 |page=102 |author-link=Patricia O'Grady}}</ref> ''[[logos]]'' rather than ''[[Mythology|mythos]]''.

Aristotle advocated the view that Thales was the first natural philosopher (''[[Ionian School (philosophy)|physiologoi]]''),<ref name=":0">[[Aristotle]], [[Metaphysics (Aristotle)|Metaphysics]] Alpha, 983b. http://data.perseus.org/citations/urn:cts:greekLit:tlg0086.tlg025.perseus-eng1:1.983b</ref><ref name="CPM">{{cite DGRBM|title=Thales|year=1870|url=https://archive.org/stream/dictionaryofgree03smituoft#page/1016|page=1016}}</ref> although this position was typically not adopted among other writers, even those within Aristotle's [[Peripatetic school]], until the view became more prominent among eighteenth-century historians.{{Sfn|Cantor|2022}} Also, while the other Seven Sages were strictly law-givers and statesmen and not speculative philosophers, Plutarch noted "it would seem that Thales was the only wise man of the time who carried his speculations beyond the realm of the practical."<ref>Plutarch, Life of Solon, 3.5 &nbsp;</ref>

=== Water as the ''arche'' ===
{{See also|Classical element#Hellenistic philosophy}}
[[File:Ostia, Baths of the Seven Sages (II) (4687819515).jpg|thumb|upright=1.25|Thales depicted at the [[Baths at Ostia|Baths of the Seven Sages]].]]

Thales's most famous idea was his philosophical and [[cosmology|cosmological]] thesis that all is water, which comes down to us through a passage from [[Aristotle]]'s ''[[Metaphysics (Aristotle)|Metaphysics]]''.<ref name=":0" /> In the work, Aristotle reported Thales's theory that the ''[[arche]]'' or originating principle of nature was [[Material monism|a single material substance]]: water. Aristotle then proceeded to proffer a number of conjectures based on his own observations to lend some credence to why Thales may have advanced this idea (though Aristotle did not hold it himself).

While Aristotle's conjecture on why Thales held water as the originating principle of matter is his own thinking, his statement that Thales held it as water is generally accepted as genuinely originating with Thales. Writing centuries later, Diogenes Laërtius also states that Thales taught "Water constituted ({{lang|grc|ὑπεστήσατο}}, 'stood under') the principle of all things."<ref>{{cite book |author=Diogenes Laërtius |url=https://en.wikisource.org/wiki/Lives_of_the_Eminent_Philosophers/Book_I#Thales |title=Lives of the Eminent Philosophers |others=Book 1, paragraph 27 |author-link=Diogenes Laërtius}}</ref>{{efn|Historian Abraham Feldman wrote that for Thales "...water united all things...all whatness is wetness".<ref name="Feldman">{{cite journal |last=Feldman |first=Abraham |title=Thoughts on Thales |journal=[[The Classical Journal]] |volume=41 |date=October 1945 |pages=4–6 |issue=1 |issn=0009-8353 |jstor=3292119}}</ref>}}

According to Aristotle:<ref name=":0" />

{{blockquote|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. …For it is necessary that there be some nature ({{lang|el|φύσις}}), either one or more than one, from which become the other things of the object being saved... [The first philosophers] do not all agree as to the number and the nature of these principles. Thales the founder of this type of philosophy says that it is water.}}

Aristotle further adds:

{{blockquote|Presumably he derived this assumption from seeing that the nutriment of everything is moist, and that heat itself is generated from moisture and depends upon it for its existence (and that from which a thing is generated is always its first principle). He derived his assumption from this; and also from the fact that the seeds of everything have a moist nature, whereas water is the first principle of the nature of moist things."<ref name="AristotleMeta">{{cite book |author=Aristotle |title=Aristotle, Metaphysics |publisher=[[Perseus Project]] |chapter=Book I 983b |chapter-url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0052%3Abook%3D1%3Asection%3D983b}}</ref>{{efn|Feldman notes "The social significance of water in the time of Thales induced him to discern through hardware and dry-goods, through soil and sperm, blood, sweat and tears, one fundamental fluid stuff...water, the most commonplace and powerful material known to him."<ref name="Feldman"/>}}}}

The 1870 book ''[[Dictionary of Greek and Roman Biography and Mythology]]'' noted:<ref name="CPM" />

{{blockquote|In his dogma that water is the origin of things, that is, that it is that out of which every thing arises, and into which every thing resolves itself, Thales may have followed [[Orphism (religion)|Orphic]] cosmogonies, while, unlike them, he sought to establish the truth of the assertion. Hence, Aristotle, immediately after he has called him the originator of philosophy brings forward the reasons which Thales was believed to have adduced in confirmation of that assertion; for that no written development of it, or indeed any book by Thales, was extant, is proved by the expressions which Aristotle uses when he brings forward the doctrines and proofs of the Milesian. (p. 1016)}}Most agree that Thales's stamp on thought is the unity of substance. Not merely the empirical claim that all is water, but the deeper philosophical claim that all is one.  For example, [[Friedrich Nietzsche]], in his ''[[Philosophy in the Tragic Age of the Greeks]]'', wrote:<ref>§ 3</ref>
{{blockquote|Greek philosophy seems to begin with an absurd notion, with the proposition that ''water'' is the primal origin and the womb of all things. Is it really necessary for us to take serious notice of this proposition? It is, and for three reasons. First, because it tells us something about the primal origin of all things; second, because it does so in language devoid of image or fable, and finally, because contained in it, if only embryonically, is the thought, "all things are one."}}

=== Mathematics ===
{{quote_box|quote={{transliteration|el|''Megiston topos: apanta gar chorei''}} {{br}} ({{lang|el|Μέγιστον τόπος· ἄπαντα γὰρ χωρεῖ.}}) {{pb}} The greatest is space, for it holds all things. |author=—attributed to Thales<ref>{{cite LotEP |chapter=Thales|loc=§ 35}}</ref> |salign=right}}

Thales was known for introducing the theoretical and practical use of [[geometry]] to Greece, and has been described as the first person in the Western world to apply deductive reasoning to geometry, making him the West's "first mathematician".<ref name="books.google.com" /><ref>{{Harvnb|Boyer|1989|p=43 (3rd ed.)|edition=3rd}}</ref><ref name="gazette">{{cite journal |last=Fletcher |first=Colin R. |date=December 1982 |title=Thales – our founder? |journal=The Mathematical Gazette |volume=66 |issue=438 |page=267 |doi=10.2307/3615512 |jstor=3615512 |s2cid=125626522}}</ref> He is also credited with the West's oldest definition of [[number]]: a "collection of units", "following the Egyptian view".<ref>{{Cite web |url=https://books.google.com/books?id=wdhMAAAAMAAJ |title=Introduction to Arithmetic|last=Nicomachus of Gerasa |year=1926 |publisher=Macmillan }}</ref><ref>A History of Greek Mathematics, Heath, p. 70</ref>

The evidence for the primacy of Thales comes to us from a book by [[Proclus]], who lived a thousand years afterward but is believed to have had a copy of [[Eudemus of Rhodes|Eudemus]]'s lost book ''History of Geometry'' (4th century BC).{{efn|While some historians, such as Colin R. Fletcher, note there could have been a precursor to Thales named by Eudemus, without the work "the question becomes mere speculation."<ref name="gazette" /> Fletcher grants there is no other viable contender to the title of first Greek mathematician, and that Thales qualifies as a practitioner in the field. "Thales had at his command the techniques of observation, experimentation, superposition and deduction... he has proved himself mathematician."<ref name="gazette" />}} Proclus wrote that Thales was the first to visit Egypt and bring the Egyptian study of mathematics to Greece, and that Thales "himself discovered many propositions and disclosed the underlying principles of many others to his successors, in some case his method being more general, in others more empirical."<ref name="gazette" /> In addition to Proclus, [[Hieronymus of Rhodes]] (3rd century BC) also cites Thales as the first Greek mathematician.{{full cn|date=March 2026}}

Proclus attributes to Thales the discovery that a circle is [[bisection|bisected]] by its diameter, that the [[Pons asinorum|base angles of an isosceles triangle are equal]] and that [[vertical angles]] are equal.<ref name="bulmer-thomas">{{cite book |last=Bulmer-Thomas |first=Ivor |author-link=Ivor Bulmer-Thomas |year=1939 |title=Selections Illustrating the History of Greek Mathematics |volume=1 |chapter=Thales |pages=164–169 |publisher=Harvard University Press |chapter-url=https://archive.org/details/selectionsillust01bulmuoft/page/164/ }}</ref> Two fundamental [[theorem]]s of elementary geometry are customarily called ''Thales's theorem'': [[Thales's theorem|one of them]] has to do with a triangle inscribed in a circle and having the circle's diameter as one side;{{r|bulmer-thomas}} the other, also called the [[intercept theorem]], is about an angle intercepted by two parallel lines, forming a pair of [[similar triangles]].

Modern scholars are skeptical that anyone in Thales's time was producing mathematical proofs to the standard of later Greek mathematics, though not enough direct evidence remains to draw firm conclusions. While Thales may have discovered some basic geometric relations and provided some justification for them, attribution to him of formal proofs is now thought to represent speculative rationalization and reconstruction by later authors, rather than concrete accomplishments of Thales himself or his contemporaries.<ref>{{cite book |last=Sidoli |first=Nathan |year=2018 |chapter=Greek mathematics |editor1-last=Jones |editor1-first=A. |editor2-last=Taub |editor2-first=L. |title=The Cambridge History of Science: Vol. 1, Ancient Science |publisher=Cambridge University Press |pages=345–373 |chapter-url=http://individual.utoronto.ca/acephalous/Sidoli_2018c.pdf }}</ref>

==== Vertical angles ====
According to one author, while visiting Egypt,<ref name="Russo" /> Thales observed that when the Egyptians drew two intersecting lines, they would measure the vertical angles to make sure that they were equal.<ref>{{cite book |last1=Shute |first1=William George |url=https://books.google.com/books?id=DIENAQAAIAAJ |title=Plane and Solid Geometry |last2=Shirk |first2=William W. |last3=Porter |first3=George F. |publisher=[[American Book Company (1890)|American Book Company]] |year=1960 |pages=25–27}}</ref> Thales concluded that one could prove that all vertical angles are equal if one accepted some general notions such as: all straight angles are equal, equals added to equals are equal, and equals subtracted from equals are equal.

==== Right triangle inscribed in a circle ====
{{Main|Thales's theorem}}
[[File:Thales' Theorem Simple.svg|thumb|upright=0.8|Thales's theorem: if {{mvar|{{overline|AC}}}} is a diameter and {{mvar|B}} is a point on the diameter's circle, the angle {{math|1=∠ ''ABC''}} is a right angle.]]
[[Pamphile of Epidaurus|Pamphila]] says that, having learnt geometry from the Egyptians, Thales was the first to inscribe in a circle a right-angled triangle, whereupon he [[Animal sacrifice|sacrificed an ox]].<ref name="gazette"/> This is sometimes cited as history's first mathematical discovery.{{sfn|Boyer|1989|p="Ionia and the Pythagoreans" p. 43}} 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.<ref name="Dicks">{{cite journal |last=Dicks |first=D. R. |title=Thales |pages=294–309 |journal=The Classical Quarterly |volume=9 |date=November 1959 |issue=2 |doi=10.1017/S0009838800041586|s2cid=246881067 }}</ref>

It is believed the Babylonians knew the theorem for special cases.<ref>de Laet, Siegfried J. (1996). ''History of Humanity: Scientific and Cultural Development''. [[UNESCO]], Volume 3, p. 14. {{isbn|92-3-102812-X}}</ref><ref>Boyer, Carl B. and [[Uta Merzbach|Merzbach, Uta C.]] (2010). ''A History of Mathematics''. John Wiley and Sons, Chapter IV. {{isbn|0-470-63056-6}}</ref>
The theorem is mentioned and proved as part of the 31st proposition in the third book of [[Euclid]]'s ''[[Euclid's Elements|Elements]]''.<ref>{{cite book |last=Heath |first=Thomas L. |date=1956 |title=The Thirteen Books of Euclid's Elements |volume=2 (Books 3–9) |edition=2nd |publisher=Dover |isbn=0486600890 |page=61 |url=https://archive.org/details/thirteenbooksofe00eucl/page/61}} Originally published by Cambridge University Press. 1st edition 1908, 2nd edition 1926.</ref>  Dante's ''[[Paradiso]]'' refers to Thales's theorem in the course of a speech.<ref>canto 13, lines 101–102</ref>

==== Similar triangles ====
{{Main|Intercept theorem}}
[[File:Thales theorem 1.png|thumb|upright=0.8|The intercept theorem: {{math|1=''DE''/''BC'' = ''AE''/''AC'' = ''AD''/''AB''}}.]]

The story is told in [[Diogenes Laërtius]], [[Pliny the Elder]], and [[Plutarch]],<ref name="gazette"/><ref>Plutarch, Moralia, The Dinner of the Seven Wise Men, [https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Plutarch/Moralia/Dinner_of_the_Seven*.html#ref5 147A]</ref> sourced from [[Hieronymus of Rhodes]], that when Thales visited [[Classical Egypt|Egypt]],<ref name="Russo" /> he measured the height of the [[pyramids]] by their shadows at the moment when his own shadow was equal to his height.{{efn|A right triangle with two equal legs is a 45-degree right triangle, all of which are similar. The length of the pyramid's shadow measured from the center of the pyramid at that moment must have been equal to its height.<ref>J J O'Connor and E F Robertson</ref>}} According to Plutarch, it pleased the pharaoh [[Amasis II|Amasis]]. More practically, Thales was said to have the ability to measure the distances of ships at sea.

These stories indicate familiarity with the intercept theorem, and for this reason the 26th proposition in the first book of Euclid's Elements was attributed to Thales.<ref>{{Cite web|url=https://books.google.com/books?id=0xY_AQAAMAAJ|title=Ars Quatuor Coronatorum: Being the Transactions of the Quatuor Coronati Lodge No. 2076, London|date=10 June 1897|publisher=W. J. Parre H, Limited }}</ref> They also indicate that he was familiar with the Egyptian ''[[seked]]'', or ''seqed'', the ratio of the run to the rise of a [[slope]] ([[cotangent]]).<ref>History of Astronomy, by Richard Perason, p. 65</ref>{{efn|The ''seked'' is at the base of problems 56, 57, 58, 59 and 60 of the [[Rhind papyrus]] — an ancient Egyptian mathematical document.}} According to Kirk & Raven,<ref name="kirk-raven" /> all you need for this feat is three straight sticks pinned at one end and knowledge of your altitude. One stick goes vertically into the ground. A second is made level. With the third you sight the ship and calculate the ''seked'' from the height of the stick and its distance from the point of insertion to the line of sight.<ref>Proclus, ''In Euclidem'', 352</ref>

=== Astronomy ===
[[File:Canova - Urania, the Muse of Astronomy Reveals to Thales the Secrets of the Skies, 1798-1799 (crop).jpg |thumb|Urania, the Muse of Astronomy, Reveals to Thales the Secrets of the Skies]]
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. He calculated the duration of the year and the timings of the [[equinoxes]] and [[solstices]]. He is additionally attributed with calculating the position of the [[Pleiades]].<ref name="kirk-raven" />

[[Plutarch]] indicates that in his day (c. AD 100) there was an extant work, the ''Astronomy'', composed in verse and attributed to Thales.<ref>Plutarch, ''[[Moralia#Books|De Pythiae oraculis]]'', [https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A2008.01.0247%3Asection%3D18 18.]</ref> While some say he left no writings, others say that he wrote ''On the Solstice'' and ''On the Equinox''. The ''Nautical Star-guide'' has also been attributed to him, but this was disputed even in ancient times.<ref name="kirk-raven" />{{efn|According to Diogenes Laertius, the Nautical Astronomy attributed to Thales was written by [[Phocus]] of Samos.}} No writing attributed to him has survived. Lobon of Argus asserted that the writings of Thales amounted to two hundred lines.<ref>D.L. I.34</ref>

==== Cosmological model ====

[[File:Floating_Earth_Thales_Anaximander.svg|thumb|Worldview of Thales (left) and pupil [[Anaximander]] (right).]]

Thales thought the [[Earth]] must be a flat disk or mound of land and dirt which is floating in an expanse of water.<ref>{{cite EB1911|last=Allman|first=George Johnston|wstitle=Thales of Miletus|volume=26|page=721}}</ref> [[Heraclitus (commentator)|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.<ref>{{Cite book|first=Roy |last=Harris|date=2005 |title=The Semantics of Science|page=31|publisher=Continuum International}}</ref>

He thought the stars were balls of earth on fire.<ref>Pseudo-Plutarch, Placita Philosopharum § 2.13</ref> He seemed to correctly gather that the moon reflects the Sun's light.<ref>Pseudo-Plutarch, Placita Philosopharum § 2.28</ref> A [[Thales (crater)|crater]] on the Moon is named in his honor.<ref>{{cite web |title=Thales |website=Gazetteer of Planetary Nomenclature |publisher=International Astronomical Union (IAU) / USGS Astrogeology Science Center |url=https://planetarynames.wr.usgs.gov/Feature/5945 |access-date=13 January 2026}}</ref><ref>{{cite web |title=Solar Eclipse Newsletter, Volume 7, Issue 2 |website=NASA Eclipse Web Site |publisher=NASA Goddard Space Flight Center |date=February 2002 |url=https://eclipse.gsfc.nasa.gov/SENL/SENL200202.pdf#page=3 |format=PDF |page=3 |access-date=13 January 2026 |quote=Thales is also honored by a lunar crater.}}</ref>

==== Meteorology ====
Rather than assuming that [[earthquake]]s were the result of supernatural whims, Thales explained them by theorizing that the Earth floats on water and that earthquakes occur when the Earth is rocked by waves.<ref>{{cite encyclopedia |year=2003 |title=Earthquakes |encyclopedia=Encyclopedia of World Environmental History |publisher=Routledge |editor-last=Krech III |editor-first=Shepard |volume=1: A–G |pages=358–364 |editor2-last=Merchant |editor2-first=Carolyn |editor3-last=McNeill |editor3-first=John Robert}}</ref><ref name="O'Grady2017" /> He is attributed with the first observation of the [[Hyades (star cluster)|Hyades]], supposed by the ancients to indicate the approach of rain when they rose with the Sun.<ref>History of Meteorology to 1800 by H. Howard Frisinger p. 3</ref> According to [[Seneca the Younger|Seneca]], Thales explained the flooding of the [[Nile]] as due to the river being beaten back by the [[etesian]] wind.<ref>History of Meteorology to 1800 by H. Howard Frisinger p. 4</ref>

==== Olive presses ====

[[File:Capernaum roman olive press by David Shankbone.jpg|thumb|An olive mill and an olive press dating from Roman times in [[Capernaum, Israel]].]]

A story from Aristotle{{r|n=apol}} recounts how Thales achieved riches from an olive harvest by [[Weather forecasting#Ancient forecasting|prediction of the weather]]. One winter, Thales reserved all the [[Olive oil extraction#Traditional method: olive press|olive presses]] in Miletus after predicting the weather and that there was a good harvest coming up. He was then able to rent them out at a high price when demand peaked in the subsequent [[bumper crop]]. This constitutes the first historically known creation and use of [[Futures contract|futures]] or [[Option (finance)|options]] (on usage of olive press), depending on whether Thales's reservations obligated or allowed (respectively) him to rent the presses during harvesttime.<ref name=deriv>George Crawford, Bidyut Sen – ''[https://books.google.com/books?id=NIIVeirctosC&pg=PA7 Derivatives for Decision Makers: Strategic Management Issues]'', John Wiley & Sons, 1996 {{isbn|978-0471129943}}</ref>{{r|n=apol}}

Aristotle explains that Thales's 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, thus disproving the taunts that philosophy was useless.<ref name=apol>Aristotle, [[Politics (Aristotle)|Politics]] 1259a [https://www.perseus.tufts.edu/cgi-bin/ptext?lookup=Aristot.+Pol.+1.1259a]</ref> He had answered the proverbial charge "[[If you're so smart, why ain't you rich?]]".{{r|n=deriv}} Aristotle also notes that [[cornering the market]] to achieve [[monopoly pricing]] is a general strategy for achieving wealth that does not rely on great wisdom or powers of prediction.{{r|n=apol}}

==== Prediction of solar eclipse ====
{{main|Eclipse of Thales}}
As mentioned above, according to Herodotus, Thales predicted a solar eclipse [[Battle of the Eclipse|which occurred during a battle]] between the [[Lydians]] and the [[Medes]].<ref name="1.74.2" /> Among eclipses of the era, only the eclipse of 28 May 585 BC reached totality in [[Anatolia]] where the war took place. 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".<ref>{{cite book |last=Singer |first=C. |title=A Short History of Science to the 19th century |publisher=Streeter Press |year=2008 |page=35}}<!--(copied from [[Thales]]--></ref><ref>{{cite book |last=Needham |first=C. W. |title=Cerebral Logic: Solving the Problem of Mind and Brain |publisher=Loose Leaf |year=1978 |isbn=978-0-398-03754-3 |page=75}}<!--(copied from [[Thales]]--></ref>

[[File:Solar eclipse 1999 4.jpg|thumb|upright=0.8|Total [[eclipse]] of the [[Sun]]]]

[[Herodotus]] writes that in the sixth year of the war, the Lydians under King [[Alyattes of Lydia|Alyattes]] and the Medes under [[Cyaxares]] were engaged in an indecisive battle when suddenly day turned into night, leading to both parties halting the fighting and negotiating a peace agreement. Herodotus also mentions that the loss of daylight had been predicted by Thales. He does not, however, mention the location of the battle.<ref>[[Herodotus]]: ''[[Histories (Herodotus)|Histories]]'' 1,74,2 ([https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0126%3Abook%3D1%3Achapter%3D74%3Asection%3D2 online])</ref>

{{blockquote|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.  In the course of it the Medes gained many victories over the Lydians, and the Lydians also gained many victories over the Medes. Among their other battles there was one night engagement. 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. This event had been foretold by Thales, the Milesian, who forewarned the Ionians of it, fixing for it the very year in which it actually took place.  The Medes and Lydians, when they observed the change, ceased fighting, and were alike anxious to have terms of peace agreed on.<ref name=Rawlinson>{{cite book |url=https://classics.mit.edu/Herodotus/history.mb.txt |title=The Histories |author=Herodotus |translator-first=George |translator-last=Rawlinson}}</ref>}}

However, based on the list of [[Median dynasty|Median kings]] and the duration of their reign reported elsewhere by Herodotus, Cyaxares died 10 years before the eclipse.<ref>Alden A. Mosshammer: ''Thales' Eclipse''. Transactions of the American Philological Association, Vol. 111, 1981, pp.&nbsp;145–155 ([https://www.jstor.org/stable/284125 JSTOR])</ref><ref>{{cite web |last=Wenskus |first=Otta |author-link=Otta Wenskus |year=2016 |title=Die angebliche Vorhersage einer Sonnenfinsternis durch Thales von Milet. Warum sich diese Legende so hartnäckig hält und warum es wichtig ist, ihr nicht zu glauben |url=https://www.uibk.ac.at/zivilrecht/team/barta/wenskus_hermes_2016.pdf |pages=2–17 |language=de |volume=144 |issue=1 |access-date=18 January 2019 |archive-date=19 January 2019 |archive-url=https://web.archive.org/web/20190119174340/https://www.uibk.ac.at/zivilrecht/team/barta/wenskus_hermes_2016.pdf |url-status=dead }}</ref>

D. R. Dicks joins other historians (F. Martini, J. L. E. Dreyer, [[Otto Neugebauer|O. Neugebauer]]) in rejecting the historicity of the eclipse story.<ref name="Dicks" /> Dicks links the story of Thales discovering the cause for a solar eclipse with Herodotus' claim that Thales discovered the cycle of the sun with relation to the solstices, and concludes "he could not possibly have possessed this knowledge which neither the Egyptians nor the Babylonians nor his immediate successors possessed."<ref name="Dicks" /> Thomas Worthen instead proposes that the battle could have been the same "night engagement" mentioned, disrupted by a predicted [[lunar eclipse|{{em|lunar}} eclipse]].<ref name="Worthen">Thomas D. Worthen, "Herodotus's Report on Thales's Eclipse," ''Electronic Antiquity'' vol. 3.7 (May 1997), [https://scholar.lib.vt.edu/ejournals/ElAnt/V3N7/worthen.html] and Thomas De Voe Worthen, "[http://tdworthen.faculty.arizona.edu/sites/tdworthen.faculty.arizona.edu/files/The%20Eclipse%20of%20585%20BCE.doc The Eclipse of 585 BCE] {{webarchive|url=https://web.archive.org/web/20110830134827/http://tdworthen.faculty.arizona.edu/sites/tdworthen.faculty.arizona.edu/files/The%20Eclipse%20of%20585%20BCE.doc|date=August 30, 2011}}"
</ref>

==== Falling into a well ====
{{See also|The Astrologer who Fell into a Well}}
Plato, Diogenes Laertius, and Hippolytus all relay the story&nbsp;that Thales was so intent upon watching the stars that he failed to watch where he was walking, and fell into a well.<ref>Theaetetus (174 A)</ref><ref>D.L. II.4–5</ref>{{efn|The Scottish philosopher [[Adam Smith]] once similarly, absent-mindedly fell into a [[Tanning (leather)|tannery]] pit.<ref>{{Cite web|url=https://fee.org/articles/adam-smith-i-had-almost-forgot-that-i-was-the-author-of-the-inquiry-concerning-the-wealth-of-nations/|title=Brilliant but Absent-Minded Adam Smith &#124; Jim Powell|first=Jim|last=Powell|date=1 March 1995|website=fee.org}}</ref>}}

<blockquote>''"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."''<ref>Theaetetus 174a</ref>
</blockquote>

=== Engineering ===
[[File:Kızılırmak River from Kapıkaya Köyü.jpg|thumb|The Halys River]]
In addition to astronomy, Thales involved himself in other practical applications of mathematics, including [[engineering]].<ref>{{MacTutor|id=Thales|title=Thales of Miletus|mode=cs1}}</ref>  Another story by Herodotus is that [[Croesus]] sent his army to the Persian territory. He was stopped by the river [[Halys River|Halys]], then unbridged. Thales then got the army across the river by digging a diversion upstream so as to reduce the flow, making it possible to cross the river.<ref>{{cite book |author=Herodotus |translator-last=Godley |translator-first=A. D. |title=Herodotus |publisher=Harvard University Press |chapter=Ch. 75 |chapter-url=https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Herodotus/1b*.html#75 }}</ref> 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.<ref name="Dicks" /> Plato praises Thales along with [[Anacharsis]], who is credited as the originator of the potter's wheel and the anchor.<ref>Plato, Republic, Book 10, section 600a</ref>

===Divinity===
[[File:Louisstgaudens1.jpg|thumb|upright|''Thales (Electricity)'', a sculpture from "The Progress of Railroading" (1908), located at the main façade of [[Washington Union Station]] ]]

According to Aristotle, Thales thought "all things are full of gods",<ref name="kirk-raven" /><ref>{{cite book |author=Aristotle |title=De Anima |title-link=De Anima |page=411a7 |author-link=Aristotle}}</ref> i.e. [[lodestone]]s had [[soul]]s because iron is attracted to them (by the force of [[magnetism]]).<ref>Nathan Ida, [https://books.google.com/books?id=YtmIBwAAQBAJ&pg=PA427 ''Engineering Electromagnetics''], Springer, 2015 {{isbn|3319078062}}</ref> The same applied to [[amber]] for its capacity to generate [[static electricity]]. The reasoning for such [[hylozoism]] or [[organicism]] seems to be if something moved, then it was alive, and if it was alive, then it must have a soul.<ref>{{cite book |last1=Sandywell |first1=Barry |title=Presocratic Reflexivity: The Construction of Philosophical Discourse C. 600-450 BC|page=97 |date=1996 |publisher=Psychology Press |isbn=978-0-415-10170-7 |url=https://books.google.com/books?id=_zWqCBdNQNMC}}</ref><ref>Farrington, B., 1944 Greek Science. Pelican</ref>

As well as gods seen in the movement caused by what came to be known as [[Electromagnetism|magnetism and electricity]], it seems Thales also had a supreme God which structured the universe:

{{blockquote| "Thales", says [[Cicero]],<ref>{{cite book |author=Cicero |author-link=Cicero |title=De Natura Deorum |page=i.,10|title-link=De Natura Deorum }}</ref> "assures that ''water'' is the principle of all things; and that God is that Mind which shaped and created all things from water."}}

According to [[Henry Fielding]] (1775), [[Diogenes Laërtius]] (1.35) affirmed that Thales posed "the independent pre-existence of God from all eternity, stating "that God was the oldest of all beings, for he existed without a previous cause even in the way of generation; that the world was the most beautiful of all things; for it was created by God."<ref>{{cite book |last=Fielding |first=Henry |author-link=Henry Fielding |year=1775 |url=https://books.google.com/books?id=C2RVAAAAcAAJ |title=An essay on conversation |publisher=[[John Bell (publisher)|John Bell]] |page=346}}</ref>

Nicholas Molinari has recently argued that Thales was influenced by the archaic water deity [[Achelous|Acheloios]], who was equated with water and worshipped in Miletus during Thales's life. 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."<ref>Nicholas J. Molinari, Acheloios, Thales, and the Origin of Philosophy: A Response to the Neo-Marxians. Oxford: Archaeopress, 2022 https://www.archaeopress.com/Archaeopress/Products/9781803270869; cf. also Nicholas J. Molinari, Concerning Water as the Archai: Acheloios, Thales, and the Origin of Philosophy. A Dissertation Providing Philosophical, Mythological, and Archaeological Responses to the Neo-Marxians, Doctoral Dissertation, Newport, RI: Salve Regina University, 2020 https://philpapers.org/rec/MOLCWA-2</ref>

==Death and legacy==
Diogenes Laërtius quotes Apollodorus as saying that Thales died at the age of 78 during the 58th [[Olympiad]] (548–545&nbsp;BC) and attributes his death to [[heat stroke]] and thirst while watching the games.<ref>{{cite web |last=Diogenes Laërtius |title=Lives of Eminent Philosophers |url=https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.01.0258%3Abook%3D1%3Achapter%3D1}}</ref>

=== Influence ===
[[File:Tales de Mileto (1906) - Veloso Salgado.png|thumb|upright=0.8|Detail of Thales from ''The Beginnings of Science'' (1906) by [[Veloso Salgado]]]]

Thales had a profound influence on other Greek thinkers and therefore on [[Western world|Western]] history. However, due to the scarcity of sources concerning Thales and the discrepancies between the accounts given in the sources that have survived, there is a scholarly debate over the extent of the influence Thales had and on which of the Greek philosophers and mathematicians that came after him.{{efn|[[Edmund Husserl]]<ref>''The Vienna Lecture''</ref> attempts to capture the new movement as follows. Philosophical man is a "new cultural configuration" based in stepping back from "pregiven tradition" and taking up a rational "inquiry into what is true in itself;" that is, an ideal of truth. }}

The first three philosophers in the Western tradition were all [[Physical cosmology|cosmologists]] from Miletus, and Thales was the very first, followed by [[Anaximander]], who was followed in turn by [[Anaximenes of Miletus|Anaximenes]]. They have been dubbed the [[Milesian School|Milesian school]]. According to the ''Suda'', Thales had been the "teacher and kinsman" of Anaximander.<ref>{{cite journal |last=Kirk |first=G. S. |author-link=G. S. Kirk |title=Popper on Science and Presocratics |year=1960 |journal=Mind |series=New Series |volume=67 |number=275 |page=330 |doi=10.1093/mind/LXIX.275.318 |doi-access=free |jstor=2251995 }}</ref>  Rather than water, Anaximander held all was made of ''[[apeiron]]'' or the unlimited; while Anaximenes, the successor of Anaximander, perhaps more like Thales with water, held that everything was composed of [[air]].<ref>{{cite web |last=Graham |first=Daniel W. |title=Anaximenes (d. 528 B.C.E.) |url=https://www.iep.utm.edu/anaximen/ |access-date=20 July 2019 |work=IEP}}</ref>

[[John Burnet (classicist)|John Burnet]] (1892) noted<ref>{{cite book |last=Burnet |first=John |url=https://archive.org/details/earlygreekphilo01burngoog |title=Early Greek Philosophy |page=[https://archive.org/details/earlygreekphilo01burngoog/page/n41 29] |year=1892|publisher=A. and C. Black }}</ref>
{{blockquote|Lastly, we have one admitted instance of a philosophic guild, that of the [[Pythagoreans]]. And it will be found that the hypothesis, if it is to be called by that name, of a regular organisation of scientific activity will alone explain all the facts. The development of doctrine in the hands of Thales, [[Anaximander]], and [[Anaximenes of Miletus|Anaximenes]], for instance, can only be understood as the elaboration of a single idea in a school with a continuous tradition.}}
As two of the first Greek mathematicians, Thales is also considered an influence on Pythagoras. According to Iamblichus, Pythagoras "had benefited by the instruction of Thales in many respects, but his greatest lesson had been to learn the value of saving time."<ref>Life of Pythagoras 3.13</ref> Early sources{{which|date=October 2021}} report that Pythagoras, in this story a pupil of Anaximander, visited Thales as a young man, and that Thales advised him to travel to Egypt to further his philosophical and mathematical studies.

Thales was also considered the teacher of the astronomer Mandrolytus of Priene.<ref>{{Cite book|url=https://books.google.com/books?id=6lnwAgAAQBAJ|title=The Philosophers of the Ancient World: An A–Z Guide|first=Trevor|last=Curnow|date=22 June 2006|publisher=A&C Black |isbn=9780715634974 }}</ref> It is possible he was also the teacher of [[Cleostratus]] of Tenedos.<ref>{{Cite journal |title=Cleostratus Redivivus |last=Webb |first=E. J. |year=1921 |journal=The Journal of Hellenic Studies|volume=41|pages=70–85 |doi=10.2307/624797 |jstor=624797 |s2cid=250254883 |url=https://archive.org/details/journalofhelleni41sociuoft/page/n147/ }}</ref>

==Notes==
{{Notelist|30em}}

== References ==
{{reflist|30em}}

== Works cited ==
* {{cite EB1911 |last=Allman |first=George Johnston  |wstitle=Thales of Miletus |volume=26 |page=721}}
* {{cite book|first=C.B.|last=Boyer|author-link=Carl Benjamin Boyer|title=A History of Mathematics|edition=2nd|<!-- rev. by Uta C. Merzbach.--> place= New York|publisher= [[Wiley (publisher)|Wiley]]|year= 1989|isbn= 978-0-471-09763-1}} (1991 pbk ed. {{isbn|0-471-54397-7}}; [https://atiekubaidillah.files.wordpress.com/2013/03/a-history-of-mathematics-3rded.pdf 2011 3rd edition])
* {{cite book |last=Burnet |first=John |author-link=John Burnet (classicist) |title=Early Greek Philosophy |publisher=[[A & C Black Ltd.]] |year=1920 |orig-year=1892}} [https://web.archive.org/web/20060807104846/http://www.classicpersuasion.org/pw/burnet/index.htm Third Edition]
* {{Cite journal |last=Cantor |first=Lea |date=2022 |title=Thales – the 'first philosopher'? A troubled chapter in the historiography of philosophy |journal=[[British Journal for the History of Philosophy]] |volume=30 |issue=5 |pages=727–750|doi=10.1080/09608788.2022.2029347 |doi-access=free }}
* [[Herodotus]], ''[[The Histories of Herodotus|Histories]]'', [[A. D. Godley]] (translator), Cambridge: [[Harvard University Press]], 1920; {{isbn|0-674-99133-8}}. [https://www.perseus.tufts.edu/cgi-bin/ptext?lookup=Hdt.+1.1.0 Online version at Perseus]
* [[Hans Joachim Störig|Störig, Hans Joachim]], ''Kleine Weltgeschichte der Philosophie''. Fischer, Frankfurt/M. 2004, {{isbn|3-596-50832-0}}.
* {{cite book |last=Lloyd |first=G. E. R. |author-link=G. E. R. Lloyd |title=Early Greek Science: Thales to Aristotle }}
* {{cite book |last=Nahm |first=Milton C. |title=Selections from Early Greek Philosophy |publisher=[[Appleton-Century-Crofts]] |year=1962 |orig-year=1934}}
* [[Pliny the Elder]], ''[[Pliny's Natural History|The Natural History]]'' (eds. John Bostock, M.D., F.R.S. H.T. Riley, Esq., B.A.) London. [[Taylor and Francis]]. (1855). [https://www.perseus.tufts.edu/cgi-bin/ptext?lookup=Plin.+Nat.+toc Online version] at the Perseus Digital Library.
* {{cite CE1913 |last=Turner |first=William |wstitle=Ionian School of Philosophy}}

== Further reading ==
* {{cite book |last=Couprie |first=Dirk L. |title=Heaven and Earth in Ancient Greek Cosmology: from Thales to Heraclides Ponticus |year=2011 |publisher=Springer |isbn=978-1441981158}}
* Enache, Cătălin (2025). ''Thales, Hippias, Aristotle and the Beginnings of Greek Philosophy''. Palgrave Macmillan. {{ISBN|978-3-031-81156-2}}
* {{cite book |last=Luchte |first=James |title=Early Greek Thought: Before the Dawn |year=2011 |publisher=Bloomsbury Publishing |location=London |isbn=978-0567353313}} 
* {{cite book |last=O'Grady |first=Patricia F. |title=Thales of Miletus: The Beginnings of Western Science and Philosophy |year=2002 |publisher=Ashgate |isbn=978-0754605331 |series=Western Philosophy Series |volume=58}}
* {{cite book |last=Mazzeo |first=Pietro |title=Talete, il primo filosofo |publisher=Editrice Tipografica |location=Bari |year=2010}}
* {{cite book |last=Molinari |first=Nicholas J. |title=Acheloios, Thales, and the Origin of Philosophy: A Response to the Neo-Marxians |year=2022 |publisher=Archaeopress |isbn=9781803270869}}
* Priou, Alex (2016). "[https://www.academia.edu/13053487/_...Going_Further_On_Down_the_Road..._The_Origin_and_Foundations_of_Milesian_Thought '...Going Further On Down the Road...': The Origin and Foundations of Milesian Thought]." ''The Review of Metaphysics'' 70, 3–31.
*{{cite book |title=A History of Western Philosophy |year=1947 |publisher=Simon & Schuster publisher |isbn=0-415-32505-6 |series=Traditio Praesocratica |location=US|language=en|last=Russell|first=Bertrand}}
*{{cite book |editor-last=Wöhrle |editor-first=Georg |title=The Milesians: Thales. Translation and additional material by Richard McKirahan |year=2014 |publisher=Walter de Gruyter |isbn=978-3-11-031525-7 |series=Traditio Praesocratica |volume=1}}

== External links ==
{{Commons category}}
{{Wikiquote|Thales}}
* {{wikisource-inline|Portal:Thales of Miletus|Thales of Miletus}}
* [https://www.iep.utm.edu/t/thales.htm Thales of Miletus from The Internet Encyclopedia of Philosophy]
* [https://mathshistory.st-andrews.ac.uk/Biographies/Thales/ Thales of Miletus] MacTutor History of Mathematics
* [https://www.mathopenref.com/thalestheorem.html Thales' Theorem – Math Open Reference] (with interactive animation)
* [https://www.mathopenref.com/thales.html Thales biography by Charlene Douglass] (with extensive bibliography)
* [https://philosophy.gr/presocratics/thales.htm Thales of Miletus] Life, Work and Testimonies by Giannis Stamatellos
* [http://demonax.info/doku.php?id=text:thales_fragments Thales Fragments] {{Webarchive|url=https://web.archive.org/web/20220424142803/http://demonax.info/doku.php?id=text:thales_fragments |date=24 April 2022 }}

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{{Ancient Greek mathematics}}
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