Thales

This deals with the pre-Socratic philosopher, Thales of Miletus.

See also: Thales (disambiguation)

Philosophically, Thales was a materialist, and a monist. Aristotle says that he (Thales) was the first to consider the basic principles and originating substance of nature. When contemplating the myriad forms and changes seen in the world, the Ionian philosophers, and first among them, Thales, posited a basic unity and permanence behind the world of phenomena and its changes, something which underlay the changes around them and which remained unchanged through the various manifestations.

He attributed all objects to a single substance manifesting in different ways to produce different objects. Science today starts with a lot more substances, the differing atoms of the nearly 100 chemical elements. But the differing atoms all have a common set of constituents, and those may manifest as invisible strings of energy, manifesting differently to constitute different objects. Science might one day find out what Thales hypothesized, that a single substance underlay all phenomena; some think they're approaching that conclusion with superstring theory.

Hawking and Mlodinow (2010) interpret Aristotle as saying that Thales was the first to develop the idea that the understanding the world was possible without resort to supernatural deities with supernatural powers. Thales thus sought the causes of phenomena in terms of naturalistic explanations rather than the personal agency of supernatural beings, whereby he proposed the concept of a natural law regulated universe, in contrast with the mythological universe governed by actions of the Olympian deities. In seeking unity in nature, he wondered about the basic principle of matter in its various forms, Thales posited a material entity, water, as this unitary substance. This is what makes him a materialist. More important was his concept that there was such a basic substance.

As Frederick Copleston stated it, summing up Thales' main philosophical contribution in his monumental History of Philosophy: ". . . the importance of this early thinker lies in the fact that he raised the question, what is the ultimate nature of the world; and not in the answer that he actually gave to that question or in his reasons, be they what they may, for giving that answer."

Thales the scientist

Later Greek writers credited Thales with numerous discoveries and advances in astronomy and geometry.

In the field of astronomy, Thales is credited by Herodotus with having predicted a solar eclipse, later identified as one which occurred in the year 585 BC. Although, in the absence of Thales' actual writings, there is currently some doubt as to the authenticity and nature of this prediction, it seems certain that he knew the causes of solar (and lunar) eclipses. He is also credited with having determined the length of the solar year and the dates of the solstices, as well as the diameters of the Sun and Moon. In each case, detailed observations over lengthy periods of time are necessary as well as the conception of how to carry out the tasks.

Thales, who had travelled to Egypt where he observed the practical usage of geometrical measuring techniques, took the first steps in placing geometry on a theoretical basis. He is credited with having demonstrated several basic propositions of geometry. Thales' method of "proof" was based on repeated, empirical measurements and induction.

Among the propositions which he demonstrated in this manner are: 1) that a circle is bisected by a diameter; 2) the angles at the base of an isoceles triangle are equal; 3) the angle of a semi-circle is a right angle; 4) if two straight lines intersect each other, the opposite angles are equal, and; 5) he demonstrated certain properties of similar triangles, including the principle of ratio, or proportionality. It is this latter property (of simiilar triangles) which Thales used to measure the previously unknown height of the pyramids as well as the distance of ships at sea.