Thales of Miletus was a pre-Socratic Greek philosopher and one of the Seven Sages of Greece. He is considered the first philosopher.

Like other pre-Socratic philosophers, no fragments of his work survived. He is only known because Plato, Aristotle, and Herodotus_ mention him in their works. However, historians have placed the activity of Thales around 585 B.C., since he was famous among astronomers for predicating a `solar eclipse`_. [1]


1   Contributions

1.1   Eclipse of Thales

The Eclipse of Thales was a `solar eclipse`_ that was, according to The Histories of Herodotus_, accurately predicted by Thales. If the account of Herodotus is accurate, the eclipse is the earliest recorded as being known in advance of its occurrence. Many historians believe that the predicted eclipse was the solar eclipse of May 28, 585 BC.

Thales was likely able to predict the eclipse because Miletus was allied with Lydia which had cultural relations with Babylonia_, and Babylonian astronomers had discovers that eclipses recur in a cycle of about nineteen years. (They could predict lunar eclipses with almost complete success, but had less success with solar eclipses because they were hampered by the fact a solar eclipse may be visible in one place and not in another. Neither he nor they knew why there is this cycle.) [1]

According to Herodotus, the appearance of an eclipse was interpreted as an omen, and interrupted a battle in a long-standing war between the Medes_ and the Lydians. The fighting immediately stopped, and they agreed to a truce.

1.2   Geometry

Thales is said to have traveled in Egypt_ and to have brought back to the Greeks the science of geometry. The Egyptians knew only rules of thumb of geometry and there is no reason to believe that Thales arrived at deductive proofs such as later Greeks discovered. He seemed to have discovered how to calculate the distance of a ship at sea from observations taken at two points on land, and how to estimate the height of a pyramid from the length of its shadow. [1]

1.3   Chemistry

According to Aristotle, Thales thought that everything was made of water.

Of the first philosophers, then, most thought the principles which were of the nature of matter were the only principles of all things... Yet they do not all agree as to the number and the nature of these principles. Thales, the founder of this type of philosophy, says the principle is water (for which reason he declared that the earth rests on water), getting the notion perhaps from seeing that the nutriment of all things is moist, and that heat itself is generated from the moist and kept alive by it (and that from which they come to be is a principle of all things). He got his notion from this fact, and from the fact that the seeds of all things have a moist nature, and that water is the origin of the nature of moist things.

Some think that even the ancients who lived long before the present generation, and first framed accounts of the gods, had a similar view of nature; for they made Ocean and Tethys the parents of creation, and described the oath of the gods as being by water, to which they give the name of Styx; for what is oldest is most honourable, and the most honourable thing is that by which one swears. It may perhaps be uncertain whether this opinion about nature is primitive and ancient, but Thales at any rate is said to have declared himself thus about the first cause.

Aristotle, Metaphysics, Book 1 Part 3, translated by W. D. Ross

This was not entirely unreasonable. Thales observed the vast quantities of water in the ocean and believed that landmasses simply floated on top. He observed also that water could take the form of a solid, liquid, or gas.

Aristotle also writes that Thales believed that magnets had a soul, because it moves iron:

Thales, too, to judge from what is recorded about him, seems to have held soul to be a motive force, since he said that the magnet has a soul in it because it moves the iron.

—Aristotle, On the Soul, Book I Part 2, translated by J. A. Smith

Later, Aristotle writes that "Thales came to the opinion that all things are full of gods":

If we must construct the soul out of the elements, there is no necessity to suppose that all the elements enter into its construction; one element in each pair of contraries will suffice to enable it to know both that element itself and its contrary. By means of the straight line we know both itself and the curved-the carpenter's rule enables us to test both-but what is curved does not enable us to distinguish either itself or the straight. Certain thinkers say that soul is intermingled in the whole universe, and it is perhaps for that reason that Thales came to the opinion that all things are full of gods. This presents some difficulties: Why does the soul when it resides in air or fire not form an animal, while it does so when it resides in mixtures of the elements, and that although it is held to be of higher quality when contained in the former? (One might add the question, why the soul in air is maintained to be higher and more immortal than that in animals.) Both possible ways of replying to the former question lead to absurdity or paradox; for it is beyond paradox to say that fire or air is an animal, and it is absurd to refuse the name of animal to what has soul in it. The opinion that the elements have soul in them seems to have arisen from the doctrine that a whole must be homogeneous with its parts. If it is true that animals become animate by drawing into themselves a portion of what surrounds them, the partisans of this view are bound to say that the soul of the Whole too is homogeneous with all its parts. If the air sucked in is homogeneous, but soul heterogeneous, clearly while some part of soul will exist in the inbreathed air, some other part will not. The soul must either be homogeneous, or such that there are some parts of the Whole in which it is not to be found.

—Aristotle, On the Soul, translated by J. A. Smith

2   Mentions

Plato mentions Thales as being consumed by philosophy:

I will illustrate my meaning, Theodorus, by the jest which the clever witty Thracian handmaid is said to have made about Thales, when he fell into a well as he was looking up at the stars. She said, that he was so eager to know what was going on in heaven, that he could not see what was before his feet. This is a jest which is equally applicable to all philosophers. For the philosopher is wholly unacquainted with his next-door neighbour; he is ignorant, not only of what he is doing, but he hardly knows whether he is a man or an animal; he is searching into the essence of man, and busy in enquiring what belongs to such a nature to do or suffer different from any other.

—Plato, Theaetetus

Aristotle mentions Thales in Nicomachean Ethics:

Philosophic wisdom is scientific knowledge, combined with intuitive reason, of the things that are highest by nature. This is why we say Anaxagoras, Thales, and men like them have philosophic but not practical wisdom, when we see them ignorant of what is to their own advantage, and why we say that they know things that are remarkable, admirable, difficult, and divine, but useless; viz. because it is not human goods that they seek.

Aristotle later explains though, that while Thales was "reproached for his poverty" he showed that philosophers can be rich if they like, but that their ambition is of another sort:

Enough has been said about the theory of wealth-getting; we will now proceed to the practical part... Works have been written upon these subjects by various persons... any one who cares for such matters may refer to their writings. It would be well also to collect the scattered stories of the ways in which individuals have succeeded in amassing a fortune; for all this is useful to persons who value the art of getting wealth. There is the anecdote of Thales the Milesian and his financial device, which involves a principle of universal application, but is attributed to him on account of his reputation for wisdom. He was reproached for his poverty, which was supposed to show that philosophy was of no use. According to the story, he knew by his skill in the stars while it was yet winter that there would be a great harvest of olives in the coming year; so, having a little money, he gave deposits for the use of all the olive-presses in Chios and Miletus, which he hired at a low price because no one bid against him. When the harvest-time came, and many were wanted all at once and of a sudden, he let them out at any rate which he pleased, and made a quantity of money. Thus he showed the world that philosophers can easily be rich if they like, but that their ambition is of another sort. He is supposed to have given a striking proof of his wisdom, but, as I was saying, his device for getting wealth is of universal application, and is nothing but the creation of a monopoly. It is an art often practiced by cities when they are want of money; they make a monopoly of provisions.

—Aristotle, Politics, Book 1 Part XI, translated by Benjamin Jowett

2.1   Seven sages

Plato includes Thales in the earliest explicit list of the seven sages:

Many of our own age and of former ages have noted that the true Lacedaemonian type of character has the love of philosophy even stronger than the love of gymnastics; they are conscious that only a perfectly educated man is capable of uttering such expressions. Such were Thales of Miletus, and Pittacus of Mitylene, and Bias of Priene, and our own Solon, and Cleobulus the Lindian, and Myson the Chenian; and seventh in the catalogue of wise men was the Lacedaemonian Chilo. All these were lovers and emulators and disciples of the culture of the Lacedaemonians, and any one may perceive that their wisdom was of this character; consisting of short memorable sentences, which they severally uttered. And they met together and dedicated in the temple of Apollo at Delphi, as the first-fruits of their wisdom, the far-famed inscriptions, which are in all men's mouths-"Know thyself," and "Nothing too much." Why do I say all this? I am explaining that this Lacedaemonian brevity was the style of primitive philosophy.

—Plato, Protagoras

3   References

[1](1, 2, 3) Bertrand Russel. 1945. The History of Western Philosophy.