Thales. The Beginnings of Western Philosophy

Thales was a native of Miletus, a Greek commercial city in Asia Minor. Regarding the years of his life we can only rely on two dates. According to Herodotus, Thales predicted the solar eclipse of May 28, 585 BC. Actually, a very interesting story goes with this date. The appearance of the eclipse had been interpreted as an omen, and the battle between the Medes and the Lydians had stopped, followed by a truce.

Miletus was allied with Lydia, and Lydia had cultural relations with Babylonia, and Babylonian astronomers had discovered that eclipses recur in a cycle of about 19 years. They could predict eclipses of the moon with pretty complete success, but as regards solar eclipses they were hampered by the fact that an eclipse may be visible in one place and not in another. How exactly Thales had predicted the solar eclipse so accurately is unknown, and it is a subject to debate until today.

The second date comes from Diogenes Laertius’ quote of Apollodorus of Athens’ chronicle, which says that Thales died at the age of 78 of heat stroke during the 58th Olympiad (548-545 BC), while watching games. With these two dates we can say that Thales lived around 624-546 BC.

Many historians of philosophy, most notably Aristotle, regard Thales as the first philosopher in Greek tradition. He is also considered one of the Seven Wise Sages of Greece (the other six include Cleobulus of Lindos, Solon of Athens, Chilon of Sparta, Bias of Priene, Pittacus of Mytilene, and Periander of Corinth, although Socrates considers Myson of Chenae instead of Periander).

Diogenes Laertius states that “according to Herodotus and Dorius and Democritus” Thales’ parents were Examyes and Cleobuline, and traces their family line up to Cadmus, the mythological Phoenician prince.

Then, Diogenes gives two conflicting reports. First says that Thales married and either fathered a son or adopted his nephew. The other says that Thales had never married, telling his mother as a young man that it was  too early to marry, and when he became old that it was too late.

Aristotle tells us of one account, when Thales reserved olive presses ahead of time at a discount only to rent them out at a high price when demand peaked, following his predictions of good harvest. Thus he showed the world that philosophers can easily be rich if they like, but that their ambition is of another sort.

We are told by one of Aristotle’s disciples, Eudemos, who wrote the first history of mathematics, that Thales introduced geometry in Greece. He had certainly visited Egypt. One story says that Thales had impressed Egyptian pharaoh by measuring the exact height of a pyramid, althought this is doubtful.

It was common knowledge among the peoples of the East that a triangle whose sides were as 3:4:5 had always a right angle. What we are told of Thales suggests that he invented some further applications of this primitive piece of knowledge. Thales understood similar triangles and right triangles, and what is more, used that knowledge in practical ways.

There are actually two theorems, which are attributed to Thales. The first one is a special case of the inscribed angle theorem, and is mentioned and proved as part of the 31st proposition, in the third book of Euclid’s Elements. It basically says, that if there is a triangle ABC, and line AC is a diameter of the circle, then the angle B is a right angle. This theorem made it possible to calculate distance of ships from the shore. Thales is said to have offered an ox to Apollo as a sacrifice of thanksgiving for the discovery.

The second Thales’ theorem, which most historians think was only attributed to him later, is an intercept theorem. When Egyptians drew two intersecting lines, they would measure the vertical angles to make sure they were equal. 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.

Thales either wrote nothing, or he wrote two works – “On the Solstice” and “On the Equinox”. Nevertheless, no writings have survived.

Before we move on to Thales’ philosophy, we must understand that his true importance lies in the fact that he was the first known thinker to seek naturalistic, rational answers to fundamental questions, rather than to ascribe objects and events to the whims of capricious gods. Thales attempted to explain natural phenomena without reference to mythology. For example, he explained earthquakes by hypothesizing that the Earth floats on water and that earthquakes occur when the Earth is rocked by waves.

First philosophers were trying to define the substance of which all material objects are composed. The idea that everything in the universe can be ultimately reduced to a single substance is the theory of monism, and Thales and his followers were the first to propose it within Western philosophy.

As Abraham Feldman puts it: “Thales saw that water was a revolutionary leveler and the elemental factor determining the subsistence and business of the world” and “the common channel of states”. So Thales concludes that all matter, regardless of its apparent properties, must be water in some stage of transformation.

Thales also notes that every landmass appears to come to an end at the water’s edge. From this he deduces that the whole of the earth must be floating on a bed of water, from which it has emerged. It seems likely that Thales viewed the Earth as solidifying from the water on which it floated and the oceans that surround it.

This view is not a foolish one, as it may be seen to a modern eye. At the beginning of previous century the received view was that everything is made of hydrogen, which is two thirds of water.

Some of the thinkers of scholasticism maintain that Thales’ choice of water was influenced by the Babylonian religion. But Feldman holds that this could not have been true, as in Babylon water is considered lifeless, whereas for Thales water is divine. He maintained that “All things are full of gods”, and to understand the nature of things was to discover the secrets of the deities, and through this knowledge open the possibility that one could be greater than the grandest Olympian.

Thales was looking for something more general, a universal substance of mind. Zeus was the personification of supreme mind, dominating all the subordinate manifestations. However, from Thales and on philosophers had a tendency to depersonify or objectify mind. The end result was a total removal of mind from substance, opening the door to a non-divine principle of action.

There is no Greek or Roman philosopher, who had not referenced to Thales, who had not tried in some degree to characterise his philosophy. We will never be able to know the exact facts about Thales’ life, but it is very important to understand his philosophy, as he was the founder of Greek philosophical tradition, and probably of whole Western Philosophy.


1) Bertrand Russell. The History of Western Philosophy.

2) Dorling Kindersley Limited (2011). The Philosophy Book.

3) John Burnet. Early Greek Philosophy.

4) Diogenes Laertius. Life of Thales.

5) Abraham Feldman. Thoughts on Thales.

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