thales biography in english

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Thales of miletus.

But the majority opinion considered him a true Milesian by descent, and of a distinguished family.

[ Thales ] first went to Egypt and thence introduced this study [ geometry ] into Greece. He discovered many propositions himself, and instructed his successors in the principles underlying many others, his method of attacking problems had greater generality in some cases and was more in the nature of simple inspection and observation in other cases.

[ Thales ] was apparently the only one of these whose wisdom stepped, in speculation, beyond the limits of practical utility, the rest acquired the reputation of wisdom in politics.

... there exists no cycle for solar eclipses visible at a given place: all modern cycles concern the earth as a whole. No Babylonian theory for predicting a solar eclipse existed at 600 BC, as one can see from the very unsatisfactory situation 400 years later, nor did the Babylonians ever develop any theory which took the influence of geographical latitude into account.

... day was all of a sudden changed into night. This event had been foretold by Thales, the Milesian, who forewarned the Ionians of it, fixing for it the very year in which it took place. The Medes and Lydians, when they observed the change, ceased fighting, and were alike anxious to have terms of peace agreed on.

... a more likely explanation seems to be simply that Thales happened to be the savant around at the time when this striking astronomical phenomenon occurred and the assumption was made that as a savant he must have been able to predict it.

Hieronymus says that [ Thales ] even succeeded in measuring the pyramids by observation of the length of their shadow at the moment when our shadows are equal to our own height.

Thales discovered how to obtain the height of pyramids and all other similar objects, namely, by measuring the shadow of the object at the time when a body and its shadow are equal in length.

... without trouble or the assistance of any instrument [ he ] merely set up a stick at the extremity of the shadow cast by the pyramid and, having thus made two triangles by the impact of the sun's rays, ... showed that the pyramid has to the stick the same ratio which the shadow [ of the pyramid ] has to the shadow [ of the stick ]

Thales is said to have travelled in Egypt, and to have thence brought to the Greeks the science of geometry. What Egyptians knew of geometry was mainly rules of thumb, and there is no reason to believe that Thales arrived at deductive proofs, such as later Greeks discovered.

• A circle is bisected by any diameter .
• The base angles of an isosceles triangle are equal .
• The angles between two intersecting straight lines are equal .
• Two triangles are congruent if they have two angles and one side equal .
• An angle in a semicircle is a right angle .

Pamphile says that Thales, who learnt geometry from the Egyptians, was the first to describe on a circle a triangle which shall be right-angled, and that he sacrificed an ox ( on the strength of the discovery ) . Others, however, including Apollodorus the calculator, say that it was Pythagoras .

[ Eudemus ] says that the method by which Thales showed how to find the distances of ships from the shore necessarily involves the use of this theorem.

Thales of Miletus taught that 'all things are water'.

...may seem an unpromising beginning for science and philosophy as we know them today; but, against the background of mythology from which it arose, it was revolutionary.

It was Thales who first conceived the principle of explaining the multitude of phenomena by a small number of hypotheses for all the various manifestations of matter.

References ( show )

• J Longrigg, Biography in Dictionary of Scientific Biography ( New York 1970 - 1990) . See THIS LINK .
• Biography in Encyclopaedia Britannica. http://www.britannica.com/biography/Thales-of-Miletus
• W S Anglin and J Lambek, The heritage of Thales ( New York, 1995) .
• R Baccou, Histoire de la science grecque de Thalès à Socrate ( Paris, 1951) .
• R S Brumbaugh, The philosophers of Greece ( Albany, N.Y., 1981) .
• Diogenes Laertius, Lives of eminent philosophers ( New York, 1925) .
• W K C Guthrie, The Greek Philosophers: From Thales to Aristotle (1975) .
• T L Heath, A History of Greek Mathematics I ( Oxford, 1921) .
• C H Kahn, Anaximander and the origins od Greek cosmology ( Indianapolis, 1994) .
• G S Kirk, J E Raven and M Schofield, The presocratic philosophers ( Cambridge, 1982) .
• O Neugebauer, The exact sciences in antiquity ( Providence, R.I., 1957) .
• B Russell, History of Western Philosophy ( London, 1961) .
• S Sambursky, The physical world of the Greeks ( London, 1956) .
• E Stamatis, The pre-Socratic philosophers : Thales of Miletus, the great scholar and philosopher ( Greek ) , Episteme kai Techne 116 (1959) .
• F Ueberweg, A History of Philosophy, from Thales to the Present Time (1972) (2 Volumes ) .
• B L van der Waerden, Science Awakening ( New York, 1954) .
• A C Bowen and B R Goldstein, Aristarchus, Thales, and Heraclitus on solar eclipses, Physis Riv. Internaz. Storia Sci. ( N.S. ) 31 (3) (1994) , 689 - 729 .
• C J Classen, Thales, in A Pauly, G Wissowa and W Kroll ( eds. ) , Reatencyclopädie der Altertumswissenschaft 10 ( Stuttgart, 1965) , 930 - 947 .
• D R Dicks, Thales, Classical Quarterly 9 (1959) , 294 - 309 .
• C R Fletcher, Thales - our founder?, Math. Gaz. 66 (438) (1982) , 266 - 272 .
• W Hartner, Eclipse periods and Thales' prediction of a solar eclipse : Historic truth and modern myth, Centaurus 14 (1969) , 60 - 71 .
• D Panchenko, Thales's prediction of a solar eclipse, J. Hist. Astronom. 25 (4) (1994) , 275 - 288 .
• D Panchenko, Thales and the origin of theoretical reasoning, Configurations 1 (3) (1993) , 387 - 414 .
• B Rizzi, Thales and the rise of science through critical discussion ( Italian ) , Physis - Riv. Internaz. Storia Sci. 22 (3 - 4) (1980) , 293 - 324 .

Additional Resources ( show )

Other pages about Thales of Miletus:

• See Thales of Miletus on a timeline
• Airy on Thales' eclipse
• The result about angles subtended in a circle
• Miller's postage stamps
• Heinz Klaus Strick biography

Other websites about Thales of Miletus:

• Dictionary of Scientific Biography
• G Don Allen
• Internet Encyclopedia of Philosophy
• Sci Hi blog

Honours ( show )

Honours awarded to Thales of Miletus

• Lunar features Crater Thales
• Popular biographies list Number 25

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Famous Mathematicians

List and Biographies of Great Mathematicians

The early philosophers used mythology to explain worldly phenomena but Thales was the first one to break away from that tradition. He employed scientific hypothesis and theories to explain natural occurrences instead of myths. According to Aristotle, Thales hypothesized the origin of all nature and matter to be water. His mathematical endeavors include the use of geometry to calculate the heights of pyramids. He is the first true mathematician about whose mathematical discoveries, historians feel fairly certain.

Thales was born in Miletus around 620 BC in a Phoenician family. It is one of most popularly believed account of his life. While others believe that he emigrated to Miletus with his parents afterwards. Thales was primarily an engineer and was aware of the existence of lodestone. He also came up with an ingenious idea to determine the length of enormous pyramids back in that age by comparing the length of shadow cast of an average human being compared with a pyramid.

Furthermore, the anecdotal record of Thales life suggests that he was a businessman as well. There is a story attached to his name how he became rich by predicting weather during an olive harvest. Thales was also involved in political affairs of defense of Anatolia’s Ionians against Persia. Moreover, he is credited for predicting the solar eclipse of 585 BC. He also calculated the equinoxes and solstices in a year. Plutarch noted in his account of Thales that an extant work called Astronomy was his effort.

Thales ventured into scientific and theoretical explanation of natural phenomena while his contemporaries relied upon Greek myths to support their theories. They would associate natural calamities to supernatural whims. However, Thales hypothesized that earthquakes occur because the Earth is rocked by the waves of the water on which it floats. The explanation was of course far from the truth but it is his non-stereotypical beliefs that paved way for scientific reasoning. He was also of the view that all matter was alive because of the movement of iron due to magnetic field and all that moved contained life.

He was recognized for his work in geometry and inventive employment of it. He held theoretical and practical both command over the subject. Thales described the method of using seked (slope) in geometry, which is a measure of the angle. Also he used trigonometry to measure the distances of ship at sea. In elementary geometry there are two theorems of Thales. One with the triangle inscribed in a circle is known as Thales’ triangle. The other theorem is named Intercept Theorem with the circle’s diameter as one leg. Thales observed that Egyptian drew two intersecting lines and through the vertical measurement they made sure the equal angles.

His cosmology thesis was his most renowned philosophical work. Aristotle is credited for noting his observations on Thales’ work in Metaphysics, which states that the originating source of all nature is one substance that is water. However, Aristotle did not share his opinion on the subject. Thales’ another strange hypothesis was his idea that the Earth is a flat object floating on the surface of water.

• Corrections

Thales of Miletus: The Father of Western Philosophy (Facts & Bio)

A philosopher, astronomer and legendary mathematician, the ancient Greek philosopher Thales of Miletus set the basis of Western thought.

Thales of Miletus was a Greek philosopher and one of the seven sages of antiquity. Aristotle considered him to be the first philosopher and his philosophical predecessor. Today, Thales is widely accepted as the first philosopher in the Western tradition. Although some of his concepts, like the idea that everything is made of water, seem out of place in the 21st century, Thales was an ingenious figure that changed the ancient world through his work in geometry, mathematics, astronomy, and, of course, philosophy.

The Life of Thales of Miletus

Thales was the son of Examyas and Cleobulina and was born in the Greek Ionian city of Miletus in Asia Minor at around 620 BCE. He belonged in one of the noble families of Miletus with possible Phoenician origins.

Not much is known about his life, but he was revered as one of the wisest Greeks of all time. He was included in the list of the seven sages of antiquity by Plato and considered to be the first philosopher by Aristotle. Traditionally, Thales is always listed as the first Presocratic philosopher . He is part of the group of the Milesian philosophers including Anaximander and Anaximenes who were his students and continuers of his thinking. In addition, due to his belief that everything derives from one and only element, water, he is also a monist philosopher just like the rest of the Milesians as well as the Ionian Greek philosopher Heraclitus .

Like most of the Presocratic philosophers, Thales was not simply a philosopher but rather a jack of all trades. He was a mathematician, an astronomer, and a mechanic. This was not something unusual. Science, theology, and philosophy were still deeply interconnected. At the time, a philosopher was a term signifying someone who loved wisdom and knowledge in all its forms. The main difference of a presocratic Greek philosopher, like Thales, from an Egyptian priest of Osiris , a Persian magus , or a Buddhist mystic, was the attempt to explain natural phenomena using natural principles. While Thales’ view that everything derives from water can be traced back to Egyptian and Semitic creation myths, his theory was an attempt at explaining the material world using natural, and not theological, principles.

Diogenes Laertius who lived in the third century CE attributes the famous Delphic maxim “know thyself” to Thales, although the ancients disagreed on the matter.

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In general, ancient sources disagreed on whether Thales of Miletus ever wrote a book. In any case, the key ideas of his thought were preserved through the work of later philosophers and scholars.

Thales’ death is placed in the 550s and there are two different versions of how he died. According to Apollodorus, he died of a heat stroke while watching the Olympic Games. However, Plato records that Thales was studying the stars of the night sky when he fell into a well. This story had a didactic value for the ancients warning them against spending too much time philosophizing, without caring about earthly matters.

However, the story could be a made-up legend. This was not uncommon in antiquity. Especially when it came to significant philosophers, politicians, and other influential personalities, the Greeks loved making up fake death stories that corresponded to the life or teachings of the deceased. Sometimes these stories were didactic and other times simply mean. In Thales’ case, it was probably a combination of the two. In the story with the well, Thales died because he lost contact with the real world after being absorbed in his pursuit of higher knowledge. Making him drown in the well was also a fun way of dismissing his theory that everything is made of water.

Thales’ Many Scientific Advancements

Thales of Miletus was not simply a theorist. He was a man who put his theoretical understanding of the world into practice. According to Herodotus , he had helped the army of King Croesus of Lydia cross the river Halys by digging a dam that divided the river into two passable straits.

As for his knowledge in Geometry and Mathematics, Thales became a symbol of the inventive man and most famously counted the height of the Great Pyramid of Giza using its shadow. He also measured the distance of ships at sea and was attributed with five theorems including the one known as the “Thales Theorem.”

His work on astronomy was also significant. His greatest and most well-known achievement was the prediction of the solar eclipse of May 28, 585 BC. He also observed and studied constellations; a feat that would be useful in the navigation of the sea. His third most important astronomical achievement was the determination of the sun’s course from solstice to solstice .

Thales Had Travelled to Egypt

“Thales… first went to Egypt and hence introduced this study [geometry] into Greece. He discovered many propositions himself, and instructed his successors in the principles underlying many others, his method of attack being in some cases more general, in others more empirical.” Proclus quoted by Thomas Little Heath

It was quite common amongst the Greeks to credit their wisest with having visited Egypt. Pythagoras, Solon, and Plato are among the most notable examples. However, in the case of Thales of Miletus, it seems that he really visited the land of the Nile as many of his achievements, like the measuring of the pyramids’ height, were set in Egypt.

Even if Thales’ visit never occurred, the legend may still point to the origins of the philosopher’s ideas. Thales was surely aware of Egyptian views about the cosmos and its creation but he managed to adapt them in a unique, unprecedented manner that led to the birth of philosophical thinking.

In addition, Geometry had originated in Egypt and Egyptian mathematical knowledge was among the most advanced in the world. Without a doubt, this knowledge passed down to Thales who became known as the one who introduced Geometry to Greece.

Thales and Monopoly

“…it is easy for philosophers to be rich if they choose, but this is not what they care about.” Aristotle, Politics 1259a

In a story told by Aristotle, Thales of Miletus provided one of the best arguments in defense of the life of a philosopher. In this story, Thales observed the celestial bodies and managed to predict that the next crop of olives would be unusually productive. He then invested in the olive presses of Miletus and Chios and, when the olives were ready to be turned to olive oil, he controlled the rate in which they were brought. This way he made a huge profit.

However, according to Aristotle, Thales did not do that in order to make money but to prove that a philosopher could live a wealthy life if they chose to. This way Thales gave an answer to everyone who called his profession useless and made fun of his poverty. The Milesian proved that a philosopher is not poor by fate but by choice at the same time signaling that there is a path of knowledge and spirituality offering higher satisfaction than the path of material wealth.

Aristotle was not convinced that this story was real. He thought that because of Thales’ wisdom, people attributed him with the tactic of monopolizing a market.

The Philosophy of Thales

As already mentioned before, Thales of Miletus is considered the first philosopher in the Western canon. His students Anaximander and Anaximenes did not follow his ideas exactly but maintained a similar direction. Since these three were born in Miletus, they are always grouped together as the Milesians.

Many also categorize Thales as an Ionian monist philosopher alongside his Milesian students and Heraclitus , the obscure philosopher from Ephesus that held that everything is made of fire and that “everything flows.”

There are many types of monism but Thales’ philosophy can be classified as substance and materialist monism. Substance monism is the idea that everything in the world can be traced back to a single substance. For Thales of Miletus, this was water. Since he also appeared to believe that matter, in the form of water, was above abstract ideas, like the soul, he was also a materialist. The monism of Thales does not mean that Thales did not recognize the existence of other substances. It rather means that he held that the primary source of everything was to be found in water. Although this sounds preposterous, in a sense, Thales was onto something.

Water, the Origin of Everything

“Thales the Milesian doth affirm that water is the principle whence all things in the universe spring.” Pseudo-Plutarch, Placita Philosophorum 1.3  

Thales believed that the world was made of water and that at some point everything would return to water.

Today, we understand that water is the universal solvent and, as far as we can tell, a necessary component for the existence of life. Now imagine being a man looking for answers to the nature of things 2,600 years ago. As you are trying to unravel the mystery of existence, you make the following observation; water is everywhere. You find a vast ocean, rivers, lakes, rain, snow, and observe that every living organism depends on this one substance called water. After all this, you observe water in all its forms; liquid, solid, and gas. Water is absorbed into the earth, and earth into the sea.

This doesn’t stop there. While you are looking for answers, you lean towards the ancient wisdom of Egyptian, Semitic, and, of course, Greek tales about the creation of the cosmos. What you discover there, is a common pattern; water is highly revered as a force of regeneration. Even the most important Greek poet, Homer, considers gods of water like Oceanus and Tethys the parents of all gods.

“For I am faring to visit the limits of the all-nurturing earth, and Oceanus, from whom the gods are sprung, and mother Tethys…” Homer, Iliad 14.246

After all this, can you really blame Thales for thinking that water is the one and only substance out of which everything derives?

The Earth Floats on the Sea?

Thales believed that the earth floated on water. This was a conclusion he had drawn after he observed that the earth presented a solidity and immobility that the sea did not. Compatible with this view, was also Thales’ belief that earthquakes were caused by the oceans’ roughness.

These ideas can also be traced back to Greek mythology where the ocean god Poseidon was also called “the Earth Shaker” and was considered to be the one responsible for earthquakes.

Furthermore, there is a debate as to whether Thales believed that the earth was flat or spherical. Although there are good reasons to suggest that Thales would have conceived the spherical shape of the earth through his astronomical endeavors, there is not sufficient evidence to back up this claim with certainty. Of course, it would not have been something preposterous for Thales to believe that the earth was round since this was a common understanding among ancient Greek philosophers and astronomers.

Did Thales Believe in the Concept of Soul?

Thales of Miletus was a naturalist philosopher trying to explain the world by observing natural phenomena. He was a materialist thinker since he attributed everything to one element, water. Despite that, he seems to have believed in the concept of the soul too. According to Aristotle, Thales was the origin of the belief that the soul is a property of things that is to be found everywhere. This idea could have been the predecessor of Plato’s concept of the soul .

“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 405 a20-22

“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.” Aristotle, On the Soul 411 a7-8

If we judge from these fragments, Thales did not even come close to Plato’s idealism . Besides his idea of the soul as a moving force of matter at a first glance appears closer to the idea of energy than the holy spirit in Christian theology. Of course, there are many ways to interpret these lines and no way of knowing exactly what Thales said. In any case, it is more likely than not, that when Thales tried to make sense of reality, he found answers in a material substance, namely water, and not in god or an abstract idea.

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Thales of Miletus

Thales of Miletus (c. 624–546 BCE) was an ancient Greek philosopher often regarded as one of the Seven Wise Men of Greece. Recognized as the first philosopher in Western history, Thales made notable contributions to various fields, including mathematics and astronomy. He is famously associated with proposing that water is the fundamental substance from which all things arise, a concept representing one of the earliest attempts to explain the natural world through reason rather than mythology. Thales’ philosophical ideas laid the groundwork for the later development of Greek philosophy and scientific inquiry.

Thales lived during a time when Greek civilization was undergoing significant cultural and intellectual developments. Miletus, a thriving city-state on the Ionian coast, was a center for trade and commerce. The exchange of ideas and goods with neighboring cultures influenced the intellectual environment in which Thales grew.

One of the remarkable aspects of Thales’ life is the absence of written records directly attributed to him. Unlike later philosophers who extensively documented their ideas, Thales’ teachings have reached us primarily through the writings of others, notably Aristotle. This lack of direct documentation makes it challenging to separate the historical Thales from the later interpretations of his ideas.

Thales is often credited with being one of the Seven Sages of Greece, a group of wise men renowned for their aphorisms and practical wisdom. However, the specifics of his teachings are not well-documented. Aristotle, in his work “Metaphysics,” attributes the belief that “everything is full of gods” to Thales, suggesting a cosmological perspective that associates divinity with the natural world.

One of Thales’ significant contributions lies in his attempt to explain the fundamental nature of the universe. He sought a single underlying substance or principle (arche) from which everything originated. Thales proposed that water was this fundamental substance, asserting that it could transform into various forms such as solid ice and gaseous vapor. While this idea might seem simplistic by modern standards, it marked a crucial shift from mythological explanations to a more systematic and rational approach to understanding the natural world.

Thales’ interest in geometry and mathematics is evident in his reputed prediction of a solar eclipse in 585 BCE. By applying his knowledge of geometry, he purportedly calculated the occurrence of the eclipse, showcasing the potential for using reason and observation to make predictions about celestial events. While the historicity of this anecdote is debated, it underscores Thales’ engagement with empirical observation and his recognition of the regularities in nature.

Another aspect of Thales’ legacy lies in his mathematical insights. He is credited with introducing geometric concepts from ancient Egypt to Greece, particularly the use of geometry in solving practical problems. According to some accounts, Thales visited Egypt and learned geometry from the Egyptians, leading to his application of geometric principles in various contexts.

The “Thales’ theorem” is a geometric proposition attributed to him. This theorem states that if A, B, and C are points on a circle where line segment BC is a diameter, then the angle at A is a right angle. While it might seem elementary, this theorem represents a foundational principle in geometry and highlights Thales’ ability to apply abstract mathematical concepts to practical situations.

Thales’ philosophical and scientific inquiries set the stage for subsequent thinkers in ancient Greece. His emphasis on seeking natural explanations for phenomena rather than resorting to mythological narratives paved the way for the development of empirical observation and rational inquiry. Thales’ approach laid the groundwork for the philosophical traditions that followed, influencing figures like Anaximander and Anaximenes, who expanded on his ideas.

While Thales’ contributions to philosophy and science are foundational, it’s essential to recognize the limitations of our knowledge about his life and works. The lack of direct writings makes it challenging to fully grasp the nuances of his philosophical doctrines. However, through the lens of later philosophical and historical accounts, we can appreciate Thales as a trailblazer who sparked a shift towards rational inquiry and systematic thinking in ancient Greece.

Thales’ influence extended beyond his own time, shaping the trajectory of Western philosophy and scientific inquiry. His exploration of the fundamental substance of the universe and his mathematical contributions laid the groundwork for the intellectual endeavors of subsequent generations. Despite the challenges of reconstructing the details of his life, Thales of Miletus remains a pivotal figure in the history of human thought, symbolizing the birth of philosophical and scientific reasoning in ancient Greece.

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Thales remains one of the most distinguished of all figures in the history of mathematics. He is considered the true father of Greek math, science, and even philosophy. Considering the impact of Greek innovations in these disciplines, Thales may actually be considered the father of these disciplines for Greece and for the world in general.

Thales’ Early Years

Thales was born around 624 BC. Due to the loss of records, there is very little known about him. It is known, however, that Thales had traveled early in life to Egypt and Babylon. During this tenure, he learned a great deal about astronomy and geometry. From his experiences, he was able to craft his own discoveries.

One of those discoveries was deductive mathematics which helped shaped theories of logic and math. He would soon develop the revolutionary concept called Thales Theorem which noted there are three points in a circle: A, B, and C. The diameter would be the line between points A and C.

Thales’ Theories and Theorems

There were several other innovative theorems that Thales would be credited with discovering. While they are not thought about as anything staggering by today’s advanced mathematics, Thales’ early research would make many simple deductions that would influence the evolution of math immensely. Attributed to Thales would be the notion a circle can be bisected by its diameter and that in an isosceles triangle, the base angles are equal.

His work was not always great though. He did have the dubious distinction of noting the earth was disk shaped and not round and they it floating on an ocean. The ocean, incidentally, was infinite. This notion was, obviously, disproved at a later point in human history. The time it took to disprove it was well over a thousand years after Thales noted his theory.

Thales as a Philosopher

While known mostly as a mathematician , Thales was also a philosopher in his own right. He championed scientific inquiry. He tried to avoid looking at mythology for answers to the origins of the natural world. He looked into the reasons for humanity’s existence and tried to do so without seeking answers in Zeus or the other gods of antiquity.

Within his philosophical musings, he was the first to truly flesh out the notion of examining things from the perspective of general principles and more rational, tight-knit hypotheses. Such innovative concepts had a profound impact on the sciences. As a result of his work, some have called him the ”Father of Science,” although this title might be a bit of an overstatement.

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Thales of Miletus: Greek Geometer

Wellcome Collection gallery / Wikimedia Commons / CC BY 4.0

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Much of our modern science, and astronomy in particular, has roots in the ancient world. In particular, the Greek philosophers studied the cosmos and tried to use the language of mathematics to explain everything. The Greek philosopher Thales was one such man. He was born around 624 BCE, and while some believe his lineage was Phoenician, most consider him to be Milesian (Miletus was in Asia Minor, now modern Turkey) and he came from a distinguished family.

It is difficult to write about Thales since none of his own writing survives. He was known to be a prolific writer, but as with so many documents from the ancient world, his vanished through the ages. He is mentioned in other people's works and seems to have been quite well-known for his time among fellow philosophers and writers. Thales was an engineer, scientist, mathematician, and philosopher interested in nature. He may have been the teacher of Anaximander (611 BC - 545 BCE), another philosopher.

Some researchers think Thales wrote a book on navigation, but there is little evidence of such a tome. In fact, if he wrote any works at all, they did not even survive until the time of Aristotle (384 BCE- 322 BCE). Even though the existence of his book is debatable, it turns out that Thales probably did define the constellation Ursa Minor .

Seven Sages

Despite the fact that much of what is known about Thales is mostly hearsay, he was definitely well-respected in ancient Greece. He was the only philosopher before Socrates to be counted among the Seven Sages. These were philosophers in the 6th century BCE who were statesmen and law-givers, and in Thales's case, a natural philosopher (scientist). 

There are reports that Thales predicted an eclipse of the Sun in 585 BCE. While the 19-year cycle for lunar eclipses was well known by this time, solar eclipses were harder to predict, since they were visible from different locations on Earth and people were not aware of the orbital motions of the Sun, Moon, and Earth that contributed to solar eclipses. Most likely, if he did make such a prediction, it was a lucky guess based on experience saying that another eclipse was due.

After the eclipse on 28 May, 585 BCE, Herodotus wrote, "Day was all of a sudden changed into night. This event had been foretold by Thales, the Milesian, who forewarned the Ionians of it, fixing for it the very year in which it took place. The Medes and Lydians, when they observed the change, ceased fighting, and were alike anxious to have terms of peace agreed on."

Impressive but Human

Thales is often credited with some impressive work with geometry. It is said he determined the heights of pyramids by measuring their shadows and could deduce the distances of ships from a vantage point onshore.

How much of our knowledge of Thales is accurate is anyone's guess. Most of what we know is due to Aristotle who wrote in his Metaphysics: "Thales of Miletus taught that 'all things are water'." Apparently Thales believed the Earth floated in water and everything came from water.

Like the absent-minded professor stereotype still popular today, Thales has been described in both glowing and derogatory tales. One story, told by Aristotle, says Thales used his skills to predict that the next season's olive crop would be bountiful. He then purchased all the olive presses and made a fortune when the prediction came true. Plato, on the other hand, told a story of how one night Thales was gazing at the sky as he walked and fell into a ditch. There was a pretty servant girl nearby who came to his rescue, who then said to him "How do you expect to understand what is going on up in the sky if you do not even see what is at your feet?"

Thales died about 547 BCE in his home of Miletus.

Edited and updated by  Carolyn Collins Petersen .

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Thales of Miletus

We explain who Thales of Miletus was, his contributions and ideas. In addition, Thales’ theorems and the main characteristics of the Milesian school.

Who was Thales of Miletus?

Thales of Miletus was an Ancient Greek philosopher and mathematician who lived between 624 BC and 548 BC in Miletus , in modern-day Turkey. His philosophy was a complete break from the prior mythological explanation of the world and it gave way to rational and logical thinking. This transformation is known as the transition from mythos to logos and is considered the beginning of Western philosophy.

Thales is one of the first physical or pre-Socratic philosophers . With him began a period which broke from the prior religious or mythological explanations regarding natural phenomena and the origin of the world. He is often referred to as the first philosopher, though this is true only for the Western world, heir to Greco-Latin thought. Thales was recognized as one of the Seven Sages of Greece.

One of the main subjects of his study was the arche or principle of all things . In Ancient Greek, the arche (ἀρχή) is the "beginning" or "origin" of all that is, both in a temporal and ontological sense. For Thales of Miletus, the originating principle of the world was water and he thus held that everything that existed was formed from it. His ideas and discoveries are considered to span disciplines such as mathematics, engineering and astronomy.

In fact, he is credited with having predicted the solar eclipse in 585 BC . However, several classical, modern and contemporary schools dedicated to the history of philosophy maintain that this is not true and that, in any case, without a direct source of the account, the hypothesis lacks foundation.

• See also: René Descartes

Main ideas of Thales of Miletus

Thales' ideas can be summarized as follows:

• For Thales, the physical universe could be explained through reason, despite its apparent disorder. He rejected any thought based on mysticism or magic.
• He investigated the primary principle of the universe and its nature. He was the first to question the nature of things and considered that, just as a piece of a mineral could be transformed into copper, all substances could be transformed into other substances.
• He believed that the first principle of all things must be material and eternal. He wondered whether at their origin all substances could have the same appearance and whether all things were in fact different aspects of the same originating substance.
• He thought the Earth as a flat disk floating on an infinite ocean covered by a celestial sphere, which was the sky.
• He was the first to introduce geometry in Greece and is credited with mathematical theorems and discoveries. Many of them are compiled in Greek mathematician Euclid’s work “Elements”.
• According to Greek historian Diogenes Laërtius, Thales was able to predict an eclipse and estimated the size of the moon in relation to the Sun.
• He was one of the first thinkers to have allegedly applied deductive reasoning.
• He believed in a universal principle (accessible through reason) which controlled and accounted for all things.
• He made no distinction between philosophy and science.

Life and work of Thales of Miletus

There are no precise details on the life of Thales of Miletus . Most of the information has come down to us from doxographers and compilers who lived at a much later time. Nonetheless, there is some widely accepted authoritative information, as is the case with Aristotle's Metaphysics , where reference is made to Thales and his work, particularly as a physicist or naturalist philosopher.

Thales was born in a region called Miletus in Ancient Greece, nowadays western Turkey . As was customary at the time, thinkers were known by their name followed by their place of birth, hence Thales is known as Thales of Miletus.

Though his theories revolutionized thought and his ideas have survived to the present day, no original writings of this thinker have been preserved, nor is he known to have written any. Therefore, there are no reliable sources that account for the authorship of many of the discoveries attributed to Thales, and most of the information that has come down to us is approximate. He is believed to have been born in Miletus in 624 BC. During his youth he allegedly visited Egypt , where he would have learned geometry and other sciences, studying with Egyptian priests.

Thales is credited with various theorems and reasonings , among which his eponymous theorems in the field of geometry stand out, even if authorship is not ascertained.

The Milesian or Ionian School

The Milesian or Ionian school was founded by Thales of Miletus, along with two contemporary philosophers and inhabitants of Miletus: Anaximander and Anaximenes. This school is considered to be the oldest in Greece and was characterized by the study of nature and the originating principle of the world, which is the reason for their appellation of "physicists". The Milesian philosophers were the first to suggest that through reason answers could be found as to certain uniformity of the universe, as well as to the alternation of day and night or summer and winter, for example.

According to Anaximander (610 BC -- 545 BC), a disciple of Thales, the originating principle of the world, or arche, was apeiron, which he defined as that which is indefinite and unlimited. Anaximenes in turn (590 BC -- 524 BC) held that the originating element of the universe was air.

From the accounts of Aristotle and Diogenes Laërtius we can certainly assert that Thales was the founder of the Ionian school of philosophy and that he believed water to be the originating substance or “the first principle of things” . This conception of water as the single material substance or arche is the reason Thales is regarded as the first philosopher in the Greek tradition or the first Western sage.

The eclipse

Another certainty that comes to us from Herodotus (a historian who lived 150 years after him) is that Thales predicted to the Ionians that there would be an eclipse during the battle between the Lydians and the Medes , on May 28, 585 BC. This prediction is considered one of the most significant events of Antiquity.

Later studies, however, have proven that Thales could not have predicted the date of the eclipse accurately nor based on a mathematical method, since his conception of the world was that of a flat planet floating on an infinite source of water. This could not have allowed him to perform the necessary calculations to measure the distance between the Earth and the Moon and between the Moon and the Sun. In fact, it is Herodotus himself who seems to point out that Thales did nothing more than indicate the year of the eclipse using a calculation period known as Saros (a cycle of 223 lunar months).

Regardless of the inaccuracies, the scarcity of reliable information and the discrepancies in the accounts regarding the Ionian philosopher, the magnitude of the profound changes he introduced in Greek and Western philosophical thought is undeniable. The mere fact that Aristotle, the highest historiographical authority of Antiquity, mentions him in the Metaphysics as the first philosopher is reason enough for him to occupy a privileged position in the history of Western philosophy.

Water as the arche or first principle

Aristotle writes in his Metaphysics that, based on his study of the nature of things, Thales concluded that all substances come out of a single ultimate substance . Following this assertion, he designated that the arche (or archai , the origin, source or principle of things that exist) was water, since it was not possible for any living being (animal or vegetable) to exist without it. As regards the concept of the first principle, Aristotle says:

(...) Thales, the founder of this philosophy, says that the originating principle is water and, for this reason, affirmed that the earth rests on it. Presumably he derived this assumption from seeing that the nutriment of everything is moist, and that heat itself is generated from moisture and depends upon it for its existence (and that from which a thing is generated is always its first principle). (Metaph. A, 983a b6 and following)

This thought and his quest to explain natural phenomena through reason made Thales the "father of philosophy". While the philosophers of his time did not accept the idea that the origin of things was water, they did accept and agree that all things that exist come from a single origin. For Anaximander, the origin of everything was the apeiron ; for Anaximenes, it was air; as for Heraclitus, it was fire and in the case of Parmenides, it was being.

Mathematical contributions and theorems of Thales

Thales is believed to have introduced geometry in Greece after traveling and studying in Egypt . Today, there are two theorems applied in the field of geometry which are ascribed to him. Thales is thought to have calculated the height of the pyramids of Giza in Egypt from their shadows.

The following two theorems are currently considered to have been discovered by Thales or, in any case, are named in his honor:

• Thales' first theorem . It states that if a line is drawn parallel to one side of a triangle to intersect the other two sides in distinct points, then the other two sides are divided in the same ratio.
• Thales' second theorem . It is applied in geometry and refers to right triangles, circles and inscribed angles. It states that the diameter of a circle always subtends a right angle to any point on the circle.

Thales is also credited with the following mathematical contributions:

• A circle is bisected by its diameter.
• The base angles of an isosceles triangle are equal.
• Opposite angles formed by intersecting straight lines are equal.
• The angle inscribed inside a semicircle is a right angle.

These findings were ascribed to Thales by Diogenes and Proclus. In any case, it should be pointed out that attributing significant discoveries to great thinkers was a common practice in antiquity.

• Guthrie, W. (1984). Historia de la filosofía griega, vol. I. Los primeros presocráticos y los pitagóricos. Gredos.
• Guthrie, W. (1953). Los filósofos griegos. De Tales a Aristóteles . FCE.
• Bernabé, A. (2008). Fragmentos presocráticos, de Tales a Demócrito . Alianza.
• “Thales of Miletus”. Britannica .
• “Thales of Miletus”. World History Encyclopedia .
• “Tales de Mileto”. Biblioteca Virtual Miguel de Cervantes .

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Thales was born more than 600 years before the birth of Christ. He entered life steeped in a culture defined by ancient mythologies. But it is Thales who is said to be among the first to toss aside centuries of nonscientific belief systems. Instead, he attempted to explain physical reality in terms of objective observation, measuring, testing and by developing solid mathematics.

Early Years of Thales

It is believed that Thales was born around the year 624 B.C. in the Ionian city of Miletus, which today is located on the western coast of Turkey. Because of the vast timescale, specific details of just where or when Thales was born are sketchy. Some ancient sources name his parents as Examyes and Cleobuline. It is possible and likely that his family was of the higher class, and perhaps even wealthy merchants. Some have traced the family of Thales back to an important Phoenician prince.

It must be acknowledged, however, that it is possible that Thales was born in Athens and later migrated to Miletus. That is because Thales is often considered to have been the “first Sage” of the famous Seven Sages. This was a school of elite philosophers known to have been established in Athens in the time period attributed to the life of Thales.

Thales the Philosopher

Up until the time of Thales, it was common for the ancient Greeks to explain natural phenomenon in terms of “actions of gods.” For example, a thunder storm might be attributed to the anger of Zeus, or an earthquake as the workings of the gods of the underworld.

But Thales was bold enough to go beyond this way of thinking in favor of more logical and rational explanations. As for earthquakes, for example, Thales proposed that the Earth’s landmasses are afloat on oceans, and so the violent action of waves might be the true cause of a shaking earth.

Contributions to Mathematics

The importance of Thales’ contributions to the understanding of mathematics cannot be overemphasized. His theoretical work in the field of geometry would have enormous influence on all western science that followed. Thales came before Euclid, after whom Euclidean Geometry is named. But without Thales, there may have never been a Euclid.

Without these kinds of fundamental understandings of geometry, so much of what we take for granted today would be impossible. The mathematical developments of Thales spurred forward a variety of practical disciplines, from navigation and architecture to engineering and a deeper understanding of astronomy.

Thales is famous for an important theorem that is named after him. The Thales Theorem states: “If A, B and C are points on a circle where the line AC is a diameter of the circle, then the angle ABC is a right angle.”

Thales and Materialism

The greatest philosophers of modern times have debated the influence of Thales with enthusiasm, but also considerable disagreement. Many point to Thales as the man who gave birth to materialism — the idea that our reality is made of something “solid.” This takes the fundamentals of physics out of the realm of mysticism or supernatural explanations and into “hard reality.”

Thales is also considered to be among the first “Naturalists,” meaning that he basically attempted to explain “nature with nature itself.” That is, rather than attributing the creation of water, rocks or trees to gods traditionally assigned to each of those, Thales sought to look at everything in terms of what the fundamental properties of substances are rather than overlaying it with a reference to a nonphysical or transcendent source.

As such, Thales was among the first to make a major break with traditional ways of thinking that had held sway for several centuries. That makes him a significant and important figure in world history.

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