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Thales of Miletus

Thales was a pre-Socratic ancient Greek philosopher, astronomer, and mathematician. He was born in  Miletus circa 624 BC and died circa 548 BC. Thales of Miletus was one of the Seven Sages of Greece and he considered to be the first philosopher in the Greek philosophical tradition. He is also historically recognized as the first individual in Western civilization to have entertained and engaged in scientific philosophy and also for being one of the first philosophers to explain natural objects and phenomena using theories and hypotheses (instead of mythology), in a precursor to modern science.

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


According to Herodotus, Thales predicted the solar eclipse of May 28, 585 BC. Among other things, Thales also pinpointed the position of Ursa Minor and thought the constellation would be useful to sailors as a guide for navigating at sea. Thales also calculated the duration of the year and the exact timings of the equinoxes and solstices, and he is attributed with the first observation of the Hyades and with calculating the position of the Pleiades.


Thales’ understanding of geometry was both theoretical and practical, and he was also known for his innovative use of geometry. It seems clear to us today that Thales understood similar triangles and right triangles, and what is more, he used this knowledge of geometry in practical ways. There is a well-known story told that he managed to measure the height of the pyramids by using their shadows at the moment when his own shadow was equal to his height. Thales used the same method to measure the distances of ships at sea and deduct that the earth is round and not flat.

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.


Thales’ cosmological thesis was his most famous philosophical position was his cosmological thesis, Aristotle in his Metaphysics, reported Thales’ hypothesis about the nature of all matter – that the originating principle of nature was water.

Influence and legacy

Thales is recognized by most philosophers as having brought something new to human thought. Philosophy. Mathematics, astronomy, and medicine already existed before Thales’ time, but Thales added something to the study of all these fields to produce a universality, which, was not in tradition before, but resulted in a new field: Philosophy.

Thales had a profound influence on other Greek thinkers and philosophers who followed him, and through them, he had a great impact on Western history. Legend has it that the great Pythagoras visited Thales when Pythagoras was a young man and Thales advised him to travel to Egypt to further his philosophical and mathematical studies.

Many philosophers of his time followed Thales’ lead in searching for explanations in nature rather than in the supernatural. Those who returned to supernatural explanations hid 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 mythical man explains the world around him based on gods and mythical 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. Logos is a way of thinking not only about individualism but also the abstract focused on sensible and continuous argumentation. This sensible and continuous argumentation lays the foundation of philosophy and its way of explaining the world.


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