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Thales of Miletus

Thales of Miletus (c. 624/623 – c. 548/545 BC) was a pre-Socratic Greek philosopher, mathematician, and astronomer from Miletus in ancient Greek Ionia. He was one of the Seven Sages of Greece. Many, most notably Aristotle, regarded him as the first philosopher in the Greek tradition, and he is otherwise historically recognized as the first individual in Western civilization known to have entertained and engaged in scientific philosophy. He can also be regarded as one of the first option traders.

Thales is recognized for breaking from the use of mythology to explain the world and the universe, and instead explaining natural objects and phenomena by theories and hypotheses, in a precursor to modern science. Almost all the other pre-Socratic philosophers followed him in explaining nature as deriving from a unity of everything based on the existence of a single ultimate substance, instead of using mythological explanations. Aristotle regarded him as the founder of the Ionian School and reported Thales’ hypothesis that the originating principle of nature and the nature of matter was a single material substance: water.

In mathematics, Thales used geometry to calculate the heights of pyramids and the distance of ships from the shore. He is the first known individual to use deductive reasoning applied to geometry, by deriving four corollaries to Thales’ theorem. He is the first known individual to whom a mathematical discovery has been attributed.

What is Thales known for? The influence and legacy of Thales of Miletus.

Astronomy

According to Herodotus, Thales predicted the solar eclipse of May 28, 585 BC. Thales also described the position of Ursa Minor and 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 the first observation of the Hyades and with calculating the position of the Pleiades.

Geometry

Thales was known for his innovative use of geometry. His understanding was theoretical as well as practical. For example, he said: Μέγιστον τόπος· ἄπαντα γαρ χωρεῖ. – The greatest is space, for it holds all things.

Thales understood similar triangles and right triangles, and what is more, used that knowledge in practical ways. There is a story told that he measured the height of the pyramids by their shadows at the moment when his own shadow was equal to his height. 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.

More practically Thales used the same method to measure the distances of ships at sea, said Eudemus as reported by Proclus (“in Euclidem”). According to 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 (Proclus, In Euclidem, 352).

Thales’ theorems

There are two theorems of Thales in elementary geometry, one known as Thales’ theorem having to do with a triangle inscribed in a circle and having the circle’s diameter as one leg, the other theorem being also called the intercept theorem. In addition, Eudemus attributed to him the discovery that a circle is bisected by its diameter, that the base angles of an isosceles triangle are equal and that vertical angles are equal.

Philosophy

Thales’ most famous philosophical position was his cosmological thesis, which comes down to us through a passage from Aristotle’s Metaphysics. In the work, Aristotle unequivocally reported Thales’ hypothesis about the nature of all matter – that the originating principle of nature was 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 didn’t hold it himself).

Influence and legacy

In the long sojourn of philosophy, there has existed hardly a philosopher or historian of philosophy who did not mention Thales and try to characterize him in some way. He is generally recognized as having brought something new to human thought. Mathematics, astronomy, and medicine already existed. Thales added something to these different collections of knowledge to produce a universality, which, as far as writing tells us, was not in tradition before, but resulted in a new field.

Thales had a profound influence on other Greek thinkers and therefore on Western history. Some believe Anaximander was a pupil of Thales. Early sources report that one of Anaximander’s more famous pupils, Pythagoras, visited Thales as a young man and that Thales advised him to travel to Egypt to further his philosophical and mathematical studies.

Many philosophers followed Thales’ lead in searching for explanations in nature rather than in the supernatural; others returned to supernatural explanations but couched them in the language of philosophy rather than of myth or of religion.

Looking specifically at Thales’ influence during the pre-Socratic era, it is clear that he stood out as one of the first thinkers who thought more in the way of logos than mythos. The difference between these two more profound ways of seeing the world is that mythos is concentrated around the stories of holy origin, while logos is concentrated around the argumentation. When the mythical man wants to explain the world the way he sees it, he explains it based on gods and powers. Mythical thought does not differentiate between things and persons and furthermore, it does not differentiate between nature and culture. The way a logos thinker would present a world view is radically different from the way of the mythical thinker. In its concrete form, logos is a way of thinking not only about individualism but also the abstract. Furthermore, it focuses on sensible and continuous argumentation. This lays the foundation of philosophy and its way of explaining the world in terms of abstract argumentation, and not in the way of gods and mythical stories.