THALES (c.625-545 B.C.)

Commonly considered to be the first (Western) philosopher, or at least, the earliest Greek enquirer into the nature of things as a whole: "the founder of this kind of philosophy" (Aristotle). Thales was the son of Examyes and Cleobuline. There is some dispute about how patrician his ancestors were. He lived in Miletus (hence 'Milesian'), a city-state in Ionia (hence 'Ionian'), a region on the south-west coast of Asia Minor (present-day Turkey). He may have been born in Miletus, and he may have visited Egypt (which was advanced in land measurement).

In addition to being a philosopher he was also a mathematician, geometer, astronomer, engineer, physicist, statesman, and he was one of the "Seven Sages" of early Greek history:


  1. Solon of Athens ("Nothing in excess")

  2. Chilon of Sparta ("Know thyself")

  3. Thales of Miletus ("To bring surety brings ruin")

  4. Bias of Priene ("Too many workers spoil the work")

  5. Cleobulus of Lindos ("Moderation is the chief good")

  6. Pittacus of Mitylene ("Know thine oppurtunity")

  7. Myson of Chen    (


Supposedly, Thales predicted successfully the year in which there was an eclipse of the sun, on May 28, 585 B.C. (while a battle was in progress between the Medes and the Lydians). This may or may not have been due to his access to eclipse records of Babylonian priests. A character in Aristophanes' Birds (414 B.C.) says about the character Meton, a town-planner, 'The man's a Thales', indicating that Thales was well-known for his mathematical and geometrical ingenuity. He may have introduced Milesian navigators to the smaller Little Bear constellation to navigate over long trips (as opposed to the Great Bear).

There is a story, probably apocryphal, of Thales being presented with a cup (or tripod) for being the wisest man living. Although various people ascribed a book entitled Nautical Astronomy to him, it is likely that he did not write a book. No quotation from Thales survives. All that we have is what others have written about him and his ideas.


Biographical Fragments (various authors)

[(1) and (2) are possibly entirely fictitious]

(1) "... just as, Theodorus, a witty and attractive Thracian servant-girl is said to have mocked Thales for falling into a well while he was observing the stars and gazing upwards; declaring that he was eager to know the things in the sky, but that what was behind him and just by his feet escaped his notice." (R, 8)

-- Plato, Theaetetus (174a4-8) in The Presocratic Philosophers [PP], edited by G. S. Kirk, J. E. Raven and M. Schofield (2nd edition, Cambridge: Cambridge University Press, 1983), p. 80


(2) "For when they reproached him because of his poverty, as though philosophy were no use, it is said that, having observed through his study of the heavenly bodies that there would be a large olive-crop, he raised a little capital while it was still winter, and paid deposits on all the olive presses in Miletus and Chios, hiring them cheaply because no one bid against him. When the appropriate time came there was a sudden rush of requests for the presses; he then hired them out on his own terms and so made a large profit, thus demonstrating that it is easy for philosophers to be rich, if they wish, but that it is not in this that they are interested." (R, 9)

-- Aristotle, Politics (1259a9-18) in PP, p. 80-81.


(3) "When he came to the Halys river, Croesus then, as I say, put his army across by the existing bridges; but, according to the common account of the Greeks, Thales the Milesian transferred the army for him. For it is said that Croesus was at a loss how his army should cross the river, since these bridges did not yet exist at this period; and that Thales, who was present in the army, made the river, which flowed on the left hand of the army, flow on the right hand also. He did so in this way: beginning upstream of the army he dug a deep channel, giving it a crescent shape, so that it should flow round the back of where the army was encamped, being diverted in this way from its old course once more by the channel, and passing the camp should flow into its old course once more. The result was that as soon as the river was divided it became fordable in both its parts."

-- PP, p. 78.


(4) "Hieronymous says that he [Thales] actually measured the pyramids by their shadow, having observed the time when our own shadow is equal to our height."

-- PP, p. 85.


(5) "Useful also was the opinion, before the destruction of Ionia, of Thales, a man of Miletus, being a Phoenician by ultimate descent, who advised the Ionians to have a single deliberative chamber, saying that it should be in Teos, for this was in the middle of Ionia; the other cities should continue to be inhabited but should be regarded as if they were demes."

-- PP, p. 78


For more on the life of Thales see the biography of Thales by Diogenes Laertius (Lives of the Philosophers) in Early Greek Philosophy [EGP], translated and edited by Jonathan Barnes (Harmondsworth, Middlesex: Penguin, 1987), p. 65-70.


Mathematical Fragments

EGP, p. 64-65. 


Philosophical Fragments



(1) "Others say that the earth rests on water. For this is the most ancient account we have received, which they say was given by Thales the Milesian, that it stays in place through floating like a log or some other such thing (for none of these rests by nature on air, but on water) -- as though the same argument did not apply to the water supporting the earth as to the earth itself." (R, 9)

-- Aristotle, On the Heavens (2.13 294a28-34), PP, p. 85.


(2) "He [Thales] said that the world is held up by water and rides like a ship, and when it is said to 'quake' it is actually rocking because of the water's movement."

-- PP, p. 93



(1) "Most of the first philosophers thought that principles in the form of matter were the only principles of all things; for the original source of all existing things, that from which a thing first comes-into-being and into which it is finally destroyed, the substance persisting but changing in its qualities, this they declare is the element and first principle of existing things, and for this reason they consider that there is no absolute coming-to-be or passing away, on the ground that such a nature is always preserved... for there must be some natural substance, either one or more than one, from which the other things come-into-being, while it is preserved. Over the number, however, and the form of this kind of principle they do not all agree; but Thales, the founder of this type of philosophy, says that it is water (and therefore declared that the earth is on water), perhaps taking this supposition from seeing the nature of all things to be moist, and the warm itself coming-to-be from this and living by this (that from which they come-to-be being the principle of all things) -- taking the supposition both from this and from the seeds of all things having a moist nature, water being the natural principle of moist things." (R, 9)

-- Aristotle, Metaphysics (1.3 983b18-27), PP, p. 89.


(2) "For moist natural substance, since it is easily formed into each different thing, is accustomed to undergo very various changes; that part of it which is exhaled is made into air, and the finest part is kindled from air into aether, while when water is compacted and changes into slime it becomes earth. Therefore Thales declared that water, of the four elements, was the most active, as it were, as cause." (R, 8)

-- PP, p. 92.




(1) "Aristotle and Hippias say that he gave a share of soul even to inanimate objects, using Magnesian stone [i.e., magnet] and amber as indications."

-- PP, p. 95


(2)  "Thales, too, seems, from what they relate, to have supposed that the soul was something kinetic, if he said that the [Magnesian] stone [i.e., a magnet] possesses soul because it moves iron."

-- PP, p. 95


(3) "And some say that it [soul] is intermingled in the universe, for which reason perhaps, Thales also thought that all things are full of gods." (R, 9)

-- Aristotle, On the Soul, 1.5 411a7-8 = 11A22, PP, p. 95



Thales appears to hold either that (1) everything is essentially water, or that (1*) everything comes from water. Also that (2) the earth is supported by water. He also appears to hold either that (3) everything is living, or that (3*) everything is interpenetrated by life.

Note that if he believes (3) or (3*) then it may be easier to understand why he believes (1) or (1*) -- for it does seem as though water is necessary for life.