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Thales of Miletus (c. 624 BC – c. 546 BC) was a pre-Socratic Greek philosopher from Miletus in Asia Minor, and one of the Seven Sages of Greece. Many, most notably Aristotle, regard him as the first philosopher in the Greek tradition. According to Bertrand Russell, “Western philosophy begins with Thales”. Thales attempted to explain natural phenomena without reference to mythology and was tremendously influential in this respect. Almost all of the other Pre-Socratic philosophers follow him in attempting to provide an explanation of ultimate substance, change, and the existence of the world—without reference to mythology. Those philosophers were also influential, and eventually Thales’ rejection of mythological explanations became an essential idea for the scientific revolution. He was also the first to define general principles and set forth hypotheses, and as a result has been dubbed the “Father of Science”, though it is argued that Democritus is actually more deserving of this title.

In mathematics, Thales used geometry to solve problems such as calculating the height of pyramids and the distance of ships from the shore. He is credited with the first use of deductive reasoning applied to geometry, by deriving four corollaries to Thales’ Theorem. As a result, he has been hailed as the first true mathematician and is the first known individual to whom a mathematical discovery has been attributed.

The current historical consensus is that Thales was born in the city of Miletus around the mid 620s BC. Miletus was an ancient Greek Ionian city on the western coast of Asia Minor (in what is today Aydin Province of Turkey), near the mouth of the Maeander River.

The dates of Thales’ life are not exactly known, but are roughly established by a few dateable events mentioned in the sources. According to Herodotus (and determination by modern methods) Thales predicted the solar eclipse of May 28, 585 BC. Diogenes Laertius quotes the chronicle of Apollodorus of Athens as saying that Thales died at the age of 78 in the 58th Olympiad (548–545 BC).

Diogenes Laertius states that (“according to Herodotus and Douris and Democritus”) Thales’ parents were Examyes and Cleobuline, then traces the family line back to Cadmus, a prince of Tyre. Diogenes then delivers conflicting reports: one that Thales married and either fathered a son (Cybisthus or Cybisthon) or adopted his nephew of the same name; the second that he never married, telling his mother as a young man that it was too early to marry, and as an older man that it was too late. Plutarch had earlier told this version: Solon visited Thales and asked him why he remained single; Thales answered that he did not like the idea of having to worry about children. Nevertheless, several years later, anxious for family, he adopted his nephew Cybisthus.

Thales involved himself in many activities, taking the role of an innovator.  But according to others he wrote nothing but two treatises, one On the Solstice and one On the Equinox, regarding all other matters as incognizable. He seems by some accounts to have been the first to study astronomy, the first to predict eclipses of the sun and to fix the solstices; so Eudemus in his History of Astronomy. It was this which gained for him the admiration of Xenophanes and Herodotus and the notice of Heraclitus and Democritus”.

Some say that he left no writings. (No writing attributed to him is known to have survived.) “And some, including Choerilus the poet, declare that he was the first to maintain the immortality of the soul. He was the first to determine the sun’s course from solstice to solstice, and according to some the first to declare the size of the sun to be one seven hundred and twentieth part of the solar circle, and the size of the moon to be the same fraction of the lunar circle. He was the first to give the last day of the month the name of Thirtieth, and the first, some say, to discuss physical problems. Aristotle and Hippias affirm that, arguing from the magnet and from amber, he attributed a soul or life even to inanimate objects. Pamphila states that, having learnt geometry from the Egyptians, he was the first to inscribe a right-angled triangle in a circle, whereupon he sacrificed an ox. Others tell this tale of Pythagoras, amongst them Apollodorus the arithmetician. (It was Pythagoras who developed to their furthest extent the discoveries attributed by Callimachus in his Iambics to Euphorbus the Phrygian, I mean “scalene triangles” and whatever else has to do with theoretical geometry)”.

Diogenes Laertius quotes two letters from Thales: one to Pherecydes of Syros offering to review his book on religion, and one to Solon, offering to keep him company on his sojourn from Athens. Thales identifies the Milesians as Athenians.

Several anecdotes suggest that Thales was not solely a thinker but was also involved in business and politics. One story recounts that he bought all the olive presses in Miletus after predicting the weather and a good harvest for a particular year. In another version of the same story, Aristotle explains that Thales reserved presses ahead of time at a discount only to rent them out at a high price when demand peaked, following his predictions of a particular good harvest. This first version of the story would constitute the first creation and use of futures, whereas the second version would be the first creation and use of options. Aristotle explains that Thales’ objective in doing this was not to enrich himself but to prove his fellow Milesians that philosophy could be useful, contrary to what they thought.

Thales’ political life had mainly to do with the involvement of the Ionians in the defense of Anatolia against the growing power of the Persians, who were then new to the region. A king had come to power in neighboring Lydia, Croesus, who was somewhat too aggressive for the size of his army. He had conquered most of the states of coastal Anatolia, including the cities of the Ionians. The story is told in Herodotus.

The Lydians were at war with the Medes, a remnant of the first wave of Iranians in the region, over the issue of refuge the Lydians had given to some Scythian soldiers of fortune inimical to the Medes. The war endured for five years, but in the sixth an eclipse of the Sun (mentioned above) spontaneously halted a battle in progress (the Battle of Halys).

It seems that Thales had predicted this solar eclipse. The Seven Sages were most likely already in existence, as Croesus was also heavily influenced by Solon of Athens, another sage. Whether Thales was present at the battle is not known, nor are the exact terms of the prediction, but based on it the Lydians and Medes made peace immediately, swearing a blood oath.

The Medes were dependencies of the Persians under Cyrus. Croesus now sided with the Medes against the Persians and marched in the direction of Iran (with far fewer men than he needed). He was stopped by the river Halys, then unbridged. This time he had Thales with him, perhaps by invitation. Whatever his status, the king gave the problem to him, and he got the army across by digging a diversion upstream so as to reduce the flow, making it possible to ford the river. The channels ran around both sides of the camp.

The two armies engaged at Pteria in Cappadocia. As the battle was indecisive but paralyzing to both sides, Croesus marched home, dismissed his mercenaries and sent emissaries to his dependents and allies to ask them to dispatch fresh troops to Sardis. The issue became more pressing when the Persian army showed up at Sardis. Diogenes Laertius tells us that Thales gained fame as a counselor when he advised the Milesians not to engage in a symmachia, a “fighting together”, with the Lydians. This has sometimes been interpreted as an alliance, but a ruler does not ally with his subjects.

Croesus was defeated before the city of Sardis by Cyrus, who subsequently spared Miletus because it had taken no action. Cyrus was so impressed by Croesus’ wisdom and his connection with the sages that he spared him and took his advice on various matters

The Ionians were now free. Herodotus says that Thales advised them to form an Ionian state; that is, a bouleuterion (“deliberative body”) to be located at Teos in the center of Ionia. The Ionian cities should be demoi, or “districts”. Miletus, however, received favorable terms from Cyrus. The others remained in an Ionian League of 12 cities (excluding Miletus now), and were subjugated by the Persians.

While Herodotus reported that most of his fellow Greeks believe that Thales did divert the river Halys to assist King Croesus’ military endeavors, he himself finds it doubtful.


The Ionic Stoa on the Sacred Way in Miletus

Diogenes Laertius tells us that the Seven Sages were created in the archonship of Damasius at Athens about 582 BC and that Thales was the first sage. The same story, however, asserts that Thales emigrated to Miletus. There is also a report that he did not become a student of nature until after his political career. Much as we would like to have a date on the seven sages, we must reject these stories and the tempting date if we are to believe that Thales was a native of Miletus, predicted the eclipse, and was with Croesus in the campaign against Cyrus.

Thales had instruction from Egyptian priest. It was fairly certain that he came from a wealthy and established family, and the wealthy customarily educated their children. Moreover, the ordinary citizen, unless he was a seafaring man or a merchant, could not afford the grand tour in Egypt, and in any case did not consort with noble lawmakers such as Solon.

He did participate in some games, most likely Panhellenic, at which he won a bowl twice. He dedicated it to Apollo at Delphi. As he was not known to have been athletic, his event was probably declamation, and it may have been victory in some specific phase of this event that led to his being designated sage.

The Greeks often invoked idiosyncratic explanations of natural phenomena by reference to the will of anthropomorphic gods and heroes. Thales, however, aimed to explain natural phenomena via a rational explanation that referenced natural processes themselves. For example, Thales attempted to explain earthquakes by hypothesizing that the Earth floats on water, and that earthquakes occur when the Earth is rocked by waves, rather than assuming that earthquakes were the result of supernatural processes. Thales was a Hylozoist (those who think matter is alive). It is unclear whether the interpretation that he treated matter as being alive might have been mistaken for his thinking the properties of nature arise directly from material processes, more consistent with modern ideas of how properties arise as emergent characteristics of complex systems involved in the processes of evolution and developmental change.

Thales, according to Aristotle, asked what was the nature (Greek Arche) of the object so that it would behave in its characteristic way. Physis (φύσις) comes from phyein (φύειν), “to grow”, related to our word “be”. (G)natura is the way a thing is “born”, again with the stamp of what it is in itself.

Aristotle characterizes most of the philosophers “at first” (πρτον) as thinking that the “principles in the form of matter were the only principles of all things”, where “principle” is arche, “matter” is hyle (“wood” or “matter”, “material”) and “form” is eidos.

Arche is translated as “principle”, but the two words do not have precisely the same meaning. A principle of something is merely prior (related to pro-) to it either chronologically or logically. An arche (from ρχειν, “to rule”) dominates an object in some way. If the arche is taken to be an origin, then specific causality is implied; that is, B is supposed to be characteristically B just because it comes from A, which dominates it.

The archai that Aristotle had in mind in his well-known passage on the first Greek scientists are not necessarily chronologically prior to their objects, but are constituents of it. For example, in pluralism objects are composed of earth, air, fire and water, but those elements do not disappear with the production of the object. They remain as archai within it, as do the atoms of the atomists.

What Aristotle is really saying is that the first philosophers were trying to define the substance(s) of which all material objects are composed. As a matter of fact, that is exactly what modern scientists are attempting to accomplish in nuclear physics, which is a second reason why Thales is described as the first western scientist.

Water as a first principle

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 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). Aristotle considered Thales’ position to be roughly the equivalent to the later ideas of Anaximenes, who held that everything was composed of air.

Aristotle laid out his own thinking about matter and form which may shed some light on the ideas of Thales, in Metaphysics 983 b6 8-11, 17-21 (The passage contains words that were later adopted by science with quite different meanings.)

“That from which is everything that exists and from which it first becomes and into which it is rendered at last, its substance remaining under it, but transforming in qualities, that they say is the element and principle of things that are. …For it is necessary that there be some nature (φύσις), either one or more than one, from which become the other things of the object being saved... Thales the founder of this type of philosophy says that it is water”.

In this quote we see Aristotle’s depiction of the problem of change and the definition of substance. He asked if an object changes, is it the same or different? In either case how can there be a change from one to the other? The answer is that the substance “is saved”, but acquires or loses different qualities (πάθη, the things you “experience”).

Aristotle conjectured that Thales reached his conclusion by contemplating that the “nourishment of all things is moist and that even the hot is created from the wet and lives by it”.

While Aristotle’s conjecture on why Thales held water was the originating principle of water is his own thinking, his statement that Thales held it was water is generally accepted as genuinely originating with Thales and he is seen as an incipient matter-and-form.

Heraclitus Homericus states that Thales drew his conclusion from seeing moist substance turn into air, slime and earth. It seems likely that Thales viewed the Earth as solidifying from the water on which it floated and which surrounded Ocean.

Writing centuries later Diogenes Laertius also states that Thales taught “Water constituted (πεστήσατο, ‘stood under’) the principle of all things”.


Later scholastic thinkers would maintain that in his choice of water Thales was influenced by Babylonian or Chaldean religion, that held that a god had begun creation by acting upon the pre-existing water. Historian Abraham Feldman holds this does not stand up under closer examination. In Babylonian religion the water is lifeless and sterile until a god acts upon it, but for Thales water itself was divine and creative. 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.

Feldman points out that while other thinkers recognized the wetness of the world “none of them was inspired to conclude that everything was ultimately aquatic”. He further points out that Thales was “a wealthy citizen of the fabulously rich Oriental port of Miletus...a dealer in the staples of antiquity, wine and oil...He certainly handled the shell-fish of the Phoenicians that secreted the dye of imperial purple”. Feldman recalls the stories of Thales measuring the distance of boats in the harbor, creating mechanical improvements for ship navigation, giving an explanation for the flooding of the Nile (vital to Egyptian agriculture and Greek trade), and changing the course of the river Halys so an army could ford it. Rather than seeing water as a barrier Thales contemplated the Ionian yearly religious gathering for athletic ritual (held on the promontory of Mycale and believed to be ordained by the ancestral kindred of Poseidon, the god of the sea). He called for the Ionian mercantile states participating in this ritual to convert it into a democratic federation under the protection of Poseidon that would hold off the forces of pastoral Persia. Feldman concludes that 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”.

Feldman considers Thales’ environment and holds that Thales would’ve seen tears, sweat, and blood as granting value to a person’s work and the means how life giving commodities travelled (whether on bodies of water or through the sweat of slaves and pack-animals). He would have seen that minerals could be processed from water such as life-sustaining salt and gold taken from rivers. He would’ve seen fish and other food stuffs gathered from it. Feldman points out that Thales held that the lodestone was alive as it drew metals to itself. He holds that Thales “living ever in sight of his beloved sea” would see water seem to draw all “traffic in wine and oil, milk and honey, juices and dyes” to itself, leading him to “a vision of the universe melting into a single substance that was valueless in itself and still the source of wealth”. Feldman concludes that for Thales “...water united all things. The social significance of water in the time of Thales induced him to discern through hardware and dry-goods, through soil and sperm, blood, sweat and tears, one fundamental fluid stuff...water, the most commonplace and powerful material known to him”. This combined with his contemporary’s idea of “spontaneous generation” allow us to see how Thales could hold that water could be divine and creative.

Feldman points to the lasting association of the theory that “all whatness is wetness” with Thales himself, pointing out that Diogenes Laertius speaks of a poem, probably a satire, where Thales is snatched to heaven by the sun, “Perhaps it was an elaborate paronomasia based on the fact that thal was the Phoenician word for dew”.

Beliefs in divinity

Thales applied his method to objects that changed to become other objects, such as water into earth (or so he thought). But what about the changing itself? Thales did address the topic, approaching it through lodestone and amber, which, when electrified by rubbing together, also attracts. It is noteworthy that the first particle known to carry electric charge, the electron, is named for the Greek word for amber, ήλεκτρον (ēlektron).

How was the power to move other things without the movers changing to be explained? Thales saw a commonality with the powers of living things to act. The lodestone and the amber must be alive, and if that were so, there could be no difference between the living and the dead. When asked why he didn’t die if there was no difference, he replied “because there is no difference.”

Aristotle defined the soul as the principle of life, that which imbues the matter and makes it live, giving it the animation, or power to act. The idea did not originate with him, as the Greeks in general believed in the distinction between mind and matter, which was ultimately to lead to a distinction not only between body and soul but also between matter and energy.

If things were alive, they must have souls. This belief was no innovation, as the ordinary ancient populations of the Mediterranean did believe that natural actions were caused by divinities. Accordingly, the sources say that Thales believed that “all things were full of gods”. In their zeal to make him the first in everything some said he was the first to hold the belief, which must have been widely known to be false.

However, Thales was looking for something more general, a universal substance of mind. That also was in the polytheism of the times. Zeus was the very personification of supreme mind, dominating all the subordinate manifestations. From Thales on, however, philosophers had a tendency to depersonify or objectify mind, as though it were the substance of animation per se and not actually a god like the other gods. The end result was a total removal of mind from substance, opening the door to a non-divine principle of action.

Classical thought, however, had proceeded only a little way along that path. Instead of referring to the person, Zeus, they talked about the great mind:

“Thales”, says Cicero, “assures that water is the principle of all things; and that God is that Mind which shaped and created all things from water”.

The universal mind appears as a Roman belief in Virgil as well:

“In the beginning, SPIRIT within (spiritus intus) strengthens Heaven and Earth,

The watery fields, and the lucid globe of Luna, and then --

Titan stars; and mind (mens) infused through the limbs

Agitates the whole mass, and mixes itself with GREAT MATTER (magno corpore)”


Thales (who died around 30 years before the time of Pythagoras and 300 years before Euclid, Eudoxus of Cnidus, and Eudemus of Rhodes) is often hailed as “the first Greek mathematician”. While some historians, such as Colin R. Fletcher, point out that there could have been a predecessor to Thales who would’ve been named in Eudemus’ lost book History of Geometry it is admitted that without the work “the question becomes mere speculation”. Fletcher holds that as there is no viable predecessor to the title of first Greek mathematician, the only question is does Thales qualify as a practitioner in that field; he holds that “Thales had at his command the techniques of observation, experimentation, superposition and deduction…he has proved himself mathematician”

The evidence for the primacy of Thales comes to us from a book by Proclus who wrote a thousand years after Thales but is believed to have had a copy of Eudemus’ book. Proclus wrote “Thales was the first to go to Egypt and bring back to Greece this study”. He goes on to tell us that in addition to applying the knowledge he gained in Egypt “He himself discovered many propositions and disclosed the underlying principles of many others to his successors, in some case his method being more general, in others more empirical”.

Other quotes from Proclus list more of Thales mathematical achievements:

“They say that Thales was the first to demonstrate that the circle is bisected by the diameter, the cause of the bisection being the unimpeded passage of the straight line through the centre”.

“[Thales] is said to have been the first to have known and to have enunciated [the theorem] that the angles at the base of any isosceles triangle are equal, though in the more archaic manner he described the equal angles as similar”.

“This theorem, that when two straight lines cut one another, the vertical and opposite angles are equal, was first discovered, as Eudemus says, by Thales, though the scientific demonstration was improved by the writer of Elements”.

Eudemus in his History of Geometry attributes this theorem [the equality of triangles having two right angles and one side equal] to Thales. For he says that the method by which Thales showed how to find the distance of ships at sea necessarily involves this method”.

Pamphila says that, having learnt geometry from the Egyptians, he [Thales] was the first to inscribe in a circle a right-angled triangle, whereupon he sacrificed an ox”.

In addition to Proclus, Hieronymus of Rhodes also cites Thales as the first Greek mathematician. Hieronymus held that Thales was able to measure the height of the pyramids by a successful application of geometry (after gathering data by using his staff and comparing its shadow to those cast by the pyramids). We receive variations of Hieronymus’ story through Diogenes Laertius, Pliny the Elder, and Plutarch. Due to the variations among testimonies, such as the “story of the sacrifice of an ox on the occasion of the discovery that the angle on a diameter of a circle is a right angle” in the version told by Diogenes Laertius being accredited to Pythagoras rather than Thales, some historians (such as D. R. Dicks) question whether such anecdotes have any historical worth whatsoever.

Practice and theory

Thales was known for his innovative use of geometry. His understanding was theoretical as well as practical. For example, he said:

“Space is the greatest thing, as it contains all things”

Topos is in Newtonian-style space, since the verb, chorei, has the connotation of yielding before things, or spreading out to make room for them, which is extension. Within this extension, things have a position. Points, lines, planes and solids related by distances and angles follow from this presumption.

Thales understood similar triangles and right triangles, and what is more, used that knowledge in practical ways. The story is told in DL (loc. cit.) 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.

This story indicates that he was familiar with the Egyptian seked, or seqed - the ratio of the run to the rise of a slope (cotangent). The seked is at the base of problems 56, 57, 58, 59 and 60 of the Rhind papyrus - an ancient Egyptian mathematics document.

In present day trigonometry, cotangents require the same units for run and rise (base and perpendicular), but the papyrus uses cubits for rise and palms for run, resulting in different (but still characteristic) numbers. Since there were 7 palms in a cubit, the seked was 7 times the cotangent.

Thales’ Theorem:

To use an example often quoted in modern reference works, suppose the base of a pyramid is 140 cubits and the angle of rise 5.25 seked. The Egyptians expressed their fractions as the sum of fractions, but the decimals are sufficient for the example. What is the rise in cubits? The run is 70 cubits, 490 palms. X, the rise, is 490 divided by 5.25 or 931⁄3 cubits. These figures sufficed for the Egyptians and Thales. We would go on to calculate the cotangent as 70 divided by 931⁄3 to get 3/4 or .75 and looking that up in a table of cotangents find that the angle of rise is a few minutes over 53 degrees.

Whether the ability to use the seked, which preceded Thales by about 1000 years, means that he was the first to define trigonometry is a matter of opinion. 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 (reference cited below), 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.

The seked is a measure of the angle. Knowledge of two angles (the seked and a right angle) and an enclosed leg (the altitude) allows you to determine by similar triangles the second leg, which is the distance. Thales probably had his own equipment rigged and recorded his own sekeds, but that is only a guess.

Thales’ Theorem is stated in another article. (Actually there are two theorems called Theorem of Thales, one 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. According to a historical Note, when Thales visited Egypt, he observed that whenever the Egyptians drew two intersecting lines, they would measure the vertical angles to make sure that 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. It would be hard to imagine civilization without these theorems.


Due to the scarcity of sources concerning Thales and the diversity among the ones we possess, there is a scholarly debate over possible influences on Thales and the Greek mathematicians that came after him.

Historian Roger L. Cooke points out that Proclus does not make any mention of Mesopotamian influence on Thales or Greek geometry, but “is shown clearly in Greek astronomy, in the use of sexagesimal system of measuring angles and in Ptolemy’s explicit use of Mesopotamian astronomical observations”. Cooke notes that it may possibly also appear in the second book of Euclid’s Elements, “which contains geometric constructions equivalent to certain algebraic relations that are frequently encountered in the cuneiform tablets”. Cooke notes “This relation however, is controversial”.

Historian B.L. Van der Waerden is among those advocating the idea of Mesopotamian influence, writing “It follows that we have to abandon the traditional belief that the oldest Greek mathematicians discovered geometry entirely by themselves…a belief that was tenable only as long as nothing was known about Babylonian mathematics. This in no way diminishes the stature of Thales; on the contrary, his genius receives only now the honour that is due to it, the honour of having developed a logical structure for geometry, of having introduced proof into geometry”.

Some historians, such as D. R. Dicks takes issue with the idea that we can determine from the questionable sources we have, just how influenced Thales was by Babylonian sources. He points out that while Thales is held to have been able to calculate an eclipse using a cycle called the “Saros “held to have been “borrowed from the Babylonians”, “The Babylonians, however, did not use cycles to predict solar eclipses, but computed them from observations of the latitude of the moon made shortly before the expected syzygy”. Dicks cites historian O. Neugebauer who relates that “No Babylonian theory for predicting solar eclipse existed at 600 B.C., as one can see from the very unsatisfactory situation 400 year later; nor did the Babylonians ever develop any theory which took the influence of geographical latitude into account”. Dicks examines the cycle referred to as ‘Saros’ - which Thales is held to have used and which is believed to stem from the Babylonians. He points out that Ptolemy makes use of this and another cycle in his book Mathematical Syntaxis but attributes it to Greek astronomers earlier than Hipparchus and not to Babylonians. Dicks notes Herodotus does relate that Thales made use of a cycle to predict the eclipse, but maintains that “if so, the fulfillment of the ‘prediction’ was a stroke of pure luck not science”. He goes further joining with other historians (F. Martini, J.L. E. Dreyer, O. Neugebauer) in rejecting the historicity of the eclipse story altogether. Dicks links the story of Thales discovering the cause for a solar eclipse with Herodotus’ claim that Thales discovered the cycle of the sun with relation to the solstices, and concludes “he could not possibly have possessed this knowledge which neither the Egyptians nor the Babylonians nor his immediate successors possessed”. Josephus is the only ancient historian that claims Thales visited Babylonia.

Herodotus wrote that the Greeks learnt the practice of dividing the day into 12 parts, about the polos, and the gnomon from the Babylonians. (The exact meaning of his use of the word polos is unknown, current theories include: “the heavenly dome”, “the tip of the axis of the celestial sphere”, or a spherical concave sundial.) Yet even Herodotus’ claims on Babylonian influence are contested by some modern historians, such as L. Zhmud, who points out that the division of the day into twelve parts (and by analogy the year) was known to the Egyptians already in the second millennium, the gnomon was known to both Egyptians and Babylonians, and the idea of the "heavenly sphere" was not used outside of Greece at this time.

Less controversial than the position that Thales learnt Babylonian mathematics is the claim he was influenced by Egyptians. Pointedly historian S. N. Bychkov holds that the idea that the base angles of an isosceles triangle are equal likely came from Egypt. This is because, when building a roof for a home - having a cross section be exactly an isosceles triangle isn't crucial (as its the ridge of the roof that must fit precisely), in contrast a symmetric square pyramid cannot have errors in the base angles of the faces or they will not fit together tightly. Historian D.R. Dicks agrees that compared to the Greeks in the era of Thales, there was a more advanced state of mathematics among the Babylonians and especially the Egyptians – “both cultures knew the correct formulae for determining the areas and volumes of simple geometrical figures such as triangles, rectangles, trapezoids, etc.; the Egyptians could also calculate correctly the volume of the frustum of a pyramid with a square base (the Babylonians used an incorrect formula for this), and used a formula for the area of a circle...which gives a value for π of 3.1605--a good approximation”. Dicks also agrees that this would have had an effect on Thales (whom the most ancient sources agree was interested in math and astronomy) but he holds that tales of Thales' travels in these lands are pure myth.

The ancient civilization and massive monuments of Egypt had “a profound and ineradicable impression on the Greeks”. They attributed to Egyptians “an immemorial knowledge of certain subjects” (including geometry) and would claim Egyptian origin for some of their own ideas to try and lend them “a respectable antiquity” (such as the “Hermetic” literature of the Alexandrian period).

Dicks holds that since Thales was a prominent figure in Greek history by the time of Eudemus but “nothing certain was known except that he lived in Miletus”. A tradition developed that as “Milesians were in a position to be able to travel widely” Thales must have gone to Egypt. As Herodotus says Egypt was the birthplace of geometry he must have learnt that while there. Since he had to have been there, surely one of the theories on Nile Flooding laid out by Herodotus must have come from Thales. Likewise as he must have been in Egypt he had to have done something with the Pyramids - thus the tale of measuring them. Similar apocryphal stories exist of Pythagoras and Plato traveling to Egypt with no corroborating evidence.

As the Egyptian and Babylonian geometry at the time was “essentially arithmetical”, they used actual numbers and “the procedure is then described with explicit instructions as to what to do with these numbers” there was no mention of how the rules of procedure were made, and nothing toward a logically arranged corpus of generalized geometrical knowledge with analytical ‘proofs’ such as we find in the words of Euclid, Archimedes, and Apollonius. So even had Thales traveled there he could not have learnt anything about the theorems he is held to have picked up there (especially because there is no evidence that any Greeks of this age could use Egyptian hieroglyphics).

Likewise until around the second century BCE and the time of Hipparchus (c. 194-120 BCE) the Babylonian general division of the circle into 360 degrees and their sexagesimal system was unknown.[ Herodotus says almost nothing about Babylonian literature and science, and very little about their history. Some historians, like P. Schnabel, hold that the Greeks only learned more about Babylonian culture from Berossus, a Babylonian priest who is said to have set up a school in Cos around 270 BCE (but to what extent this had in the field of geometry is contested).

Dicks points out that the primitive state of Greek mathematics and astronomical ideas exhibited by the peculiar notions of Thales’ successors (such as Anaximander, Anaximenes, Xenophanes, and Heraclitus), which historian J. L. Heiberg calls “a mixture of brilliant intuition and childlike analogies”, argues against the assertions from writers in late antiquity that Thales discovered and taught advanced concepts in these fields.


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.

Ever since, interested persons have been asking what that new something is. Answers fall into (at least) two categories, the theory and the method. Once an answer has been arrived at, the next logical step is to ask how Thales compares to other philosophers, which leads to his classification (rightly or wrongly).


The most natural epithets of Thales are “materialist” and “naturalist”, which are based on ousia and physis. The Catholic Encyclopedia notes that Aristotle called him a physiologist, with the meaning “student of nature”. On the other hand, he would have qualified as an early physicist, as did Aristotle. They studied corpora, “bodies”, the medieval descendants of substances.

Most agree that Thales’ stamp on thought is the unity of substance, hence Bertrand Russell:

“The view that all matter is one is quite a reputable scientific hypothesis”.

“...But it is still a handsome feat to have discovered that a substance remains the same in different states of aggregation”.

Russell was only reflecting an established tradition; for example: Nietzsche, in his Philosophy in the Tragic Age of the Greeks, wrote:

“Greek philosophy seems to begin with an absurd notion, with the proposition that water is the primal origin and the womb of all things. Is it really necessary for us to take serious notice of this proposition? It is, and for three reasons. First, because it tells us something about the primal origin of all things; second, because it does so in language devoid of image or fable, and finally, because contained in it, if only embryonically, is the thought, ‘all things are one’.”

This sort of materialism, however, should not be confused with deterministic materialism. Thales was only trying to explain the unity observed in the free play of the qualities. The arrival of uncertainty in the modern world made possible a return to Thales; for example, John Elof Boodin writes (“God and Creation”):

“We cannot read the universe from the past...”

Boodin defines an “emergent” materialism, in which the objects of sense emerge uncertainly from the substrate. Thales is the innovator of this sort of materialism.

Rise of theoretical inquiry

In the West, Thales represents a new kind of inquiring community as well. Edmund Husserl attempts to capture the new movement as follows. Philosophical man is a “new cultural configuration” based in stepping back from “pregiven tradition” and taking up a rational “inquiry into what is true in itself”; that is, an ideal of truth. It begins with isolated individuals such as Thales, but they are supported and cooperated with as time goes on. Finally the ideal transforms the norms of society, leaping across national borders.


The term “Pre-Socratic” derives ultimately from the philosopher Aristotle, who distinguished the early philosophers as concerning themselves with substance.

Diogenes Laertius on the other hand took a strictly geographic and ethnic approach. Philosophers were either Ionian or Italian. He used “Ionian” in a broader sense, including also the Athenian academics, who were not Pre-Socratics. From a philosophic point of view, any grouping at all would have been just as effective. There is no basis for an Ionian or Italian unity. Some scholars, however, concede to Diogenes' scheme as far as referring to an “Ionian” school. There was no such school in any sense.

The most popular approach refers to a Milesian school, which is more justifiable socially and philosophically. They sought for the substance of phenomena and may have studied with each other. Some ancient writers qualify them as Milesioi, of Miletus.

Influence on others

Thales (Electricity), sculpture from “The Progress of Railroading” (1908), main facade of Union Station (Washington, DC)

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.

Reliability of sources

Thales, Nuremberg Chronicle.

Because of Thales’ elevated status in Greek culture an intense interest and admiration followed his reputation. Due to this following, the oral stories about his life were open to amplification and historical fabrication, even before they were written down generations later. Most modern dissension comes from trying to interpret what we know, in particular, distinguishing legend from fact.

Historian D.R. Dicks and other historians divide the ancient sources about Thales into those before 320 BCE and those after that year (some such as Proclus writing in the 5th century C.E. and Simplicius of Cilicia in the 6th century C.E. writing nearly a millennium after his era). The first category includes Herodotus, Plato, Aristotle, Aristophanes, and Theophrastus among others. The second category includes Plautus, Aetius, Eusebius, Plutarch, Josephus, Iamblichus, Diogenes LaërtiusTheon of Smyrna, Apuleius, Clement of Alexandria, Pliny the Elder, and John Tzetzes among others.

The earliest sources on Thales (living before 320 BCE) are often the same for the other Milesian philosophers (Anaximander, and Anaximenes). These sources were either roughly contemporaneous (such as Herodotus) or lived within a few hundred years of his passing. Moreover, they were writing from an oral tradition that was widespread and well known in the Greece of their day.

The latter sources on Thales are several “ascriptions of commentators and compilers who lived anything from 700 to 1,000 years after his death” which include “anecdotes of varying degrees of plausibility” and in the opinion of some historians (such as D. R. Dicks) of “no historical worth whatsoever”. Dicks points out that there is no agreement “among the ‘authorities’ even on the most fundamental facts of his life--e.g. whether he was a Milesian or a Phoenician, whether he left any writings or not, whether he was married or single-much less on the actual ideas and achievements with which he is credited”.

Contrasting the work of the more ancient writers with those of the later, Dicks points out that in the works of the early writers Thales and the other men who would be hailed as “the Seven Sages of Greece” had a different reputation than that which would be assigned to them by later authors. Closer to their own era, Thales, Solon, Bias of Priene, Pittacus of Mytilene and others were hailed as “essentially practical men who played leading roles in the affairs of their respective states, and were far better known to the earlier Greeks as lawgivers and statesmen than as profound thinkers and philosophers”. For example, Plato praises him (coupled with Anacharsis) for being the originator of the potter’s wheel and the anchor.

Only in the writings of the second group of writers (working after 320 BCE) do “we obtain the picture of Thales as the pioneer in Greek scientific thinking, particularly in regard to mathematics and astronomy which he is supposed to have learnt about in Babylonia and Egypt”. Rather than “the earlier tradition [where] he is a favourite example of the intelligent man who possesses some technical ‘know how’...the later doxographers [such as Dicaearchus in the latter half of the fourth century BCE] foist on to him any number of discoveries and achievements, in order to build him up as a figure of superhuman wisdom”.

Dicks points out a further problem arises in the surviving information on Thales, for rather than using ancient sources closer to the era of Thales, the authors in later antiquity (‘epitomators, excerptors, and compilers’) actually “preferred to use one or more intermediaries, so that what we actually read in them comes to us not even at second, but at third or fourth or fifth hand. ...Obviously this use of intermediate sources, copied and recopied from century to century, with each writer adding additional pieces of information of greater or less plausibility from his own knowledge, provided a fertile field for errors in transmission, wrong ascriptions, and fictitious attributions”. Dicks points out that “certain doctrines that later commentators invented for Thales...were then accepted into the biographical tradition” being copied by subsequent writers who were then cited by those coming after them “and thus, because they may be repeated by different authors relying on different sources, may produce an illusory impression of genuineness”.

Doubts even exist when considering the philosophical positions held to originate in Thales “in reality these stem directly from Aristotle’s own interpretations which then became incorporated in the doxographical tradition as erroneous ascriptions to Thales”. (The same treatment was given by Aristotle to Anaxagoras.)

Most philosophic analyses of the philosophy of Thales come from Aristotle, a professional philosopher, tutor of Alexander the Great, who wrote 200 years after Thales death. Aristotle, judging from his surviving books, does not seem to have access to any works by Thales, although he probably had access to works of other authors about Thales, such as Herodotus, Hecataeus, Plato etc., as well as others whose work is now extinct. It was Aristotle's express goal to present Thales work not because it was significant in itself, but as a prelude to his own work in natural philosophy. Geoffrey Kirk and John Raven, English compilers of the fragments of the Pre-Socratics, assert that Aristotle’s “judgments are often distorted by his view of earlier philosophy as a stumbling progress toward the truth that Aristotle himself revealed in his physical doctrines”. There was also an extensive oral tradition. Both the oral and the written were commonly read or known by all educated men in the region.

Aristotle’s philosophy had a distinct stamp: it professed the theory of matter and form, which modern scholastics have dubbed hylomorphism. Though once very widespread, it was not generally adopted by rationalist and modern science, as it mainly is useful in metaphysical analyses, but does not lend itself to the detail that is of interest to modern science. It is not clear that the theory of matter and form existed as early as Thales, and if it did, whether Thales espoused it.

While some historians, like B. Snell, maintain that Aristotle was relying on a pre-Platonic written record by Hippias rather than oral tradition, this is a controversial position. Representing the scholarly consensus Dicks states that “the tradition about him even as early as the fifth century B.C., was evidently based entirely on hearsay....It would seem that already by Aristotle's time the early Ionians were largely names only to which popular tradition attached various ideas or achievements with greater or less plausibility”. He points out that works confirmed to have existed in the sixth century BCE by Anaximander and Xenophanes had already disappeared by the fourth century BCE, so the chances of Pre-Socratic material surviving to the age of Aristotle is almost nil (even less likely for Aristotle's pupils Theophrastus and Eudemus and less likely still for those following after them).

The main secondary source concerning the details of Thales’ life and career is Diogenes Laertius, “Lives of Eminent Philosophers”. This is primarily a biographical work, as the name indicates. Compared to Aristotle, Diogenes is not much of a philosopher. He is the one who, in the Prologue to that work, is responsible for the division of the early philosophers into “Ionian” and “Italian”, but he places the Academics in the Ionian school and otherwise evidences considerable disarray and contradiction, especially in the long section on forerunners of the “Ionian School”. Diogenes quotes two letters attributed to Thales, but Diogenes wrote some eight centuries after Thales' death and that his sources often contained “unreliable or even fabricated information”, hence the concern for separating fact from legend in accounts of Thales.

It is due to this use of hearsay and a lack of citing original sources that leads some historians, like Dicks and Werner Jaeger, to look at the late origin of the traditional picture of Pre-Socratic philosophy and view the whole idea as a construct from a later age, “the whole picture that has come down to us of the history of early philosophy was fashioned during the two or three generations from Plato to the immediate pupils of Aristotle”.




Herodotus, Duris, and Democritus are agreed that Thales was the son of Examyas and Cleobulina, and belonged to the Thelidae who are Phoenicians, and among the noblest of the descendants of Cadmus and Agenor. As Plato testifies, he was one of the Seven Sages. He was the first to receive the name of Sage, in the archonship of Damasias at Athens, when the term was applied to all the Seven Sages, as Demetrius of Phalerum mentions in his List of Archons. He was admitted to citizenship at Miletus when he came to that town along with Nileos, who had been expelled from Phoenicia. Most writers, however, represent him as a genuine Milesian and of a distinguished family.

After engaging in politics he became a student of nature. According to some he left nothing in writing; for the Nautical Astronomy attributed to him is said to be by Phocus of Samos. Callimachus knows him as the discoverer of the Ursa Minor; for he says in his Iambics:


Who first of men the course made plain

Of those small stars we call the Wain,

Whereby Phoenicians sail the main.


But according to others he wrote nothing but two treatises, one On the Solstice and one On the Equinox, regarding all other matters as incognizable. He seems by some accounts to have been the first to study astronomy, the first to predict eclipses of the sun and to fix the solstices; so Eudemus in his History of Astronomy. It was this which gained for him the admiration of Xenophanes and Herodotus and the notice of Heraclitus and Democritus.

And some, including Choerilus the poet, declare that he was the first to maintain the immortality of the soul. He was the first to determine the sun's course from solstice to solstice, and according to some the first to declare the size of the sun to be one seven hundred and twentieth part of the solar circle, and the size of the moon to be the same fraction of the lunar circle. He was the first to give the last day of the month the name of Thirtieth, and the first, some say, to discuss physical problems.

Aristotle and Hippias affirm that, arguing from the magnet and from amber, he attributed a soul or life even to inanimate objects. Pamphila states that, having learnt geometry from the Egyptians, he was the first to inscribe a right-angled triangle in a circle, whereupon he sacrificed an ox. Others tell this tale of Pythagoras, amongst them Apollodorus the arithmetician. (It was Pythagoras who developed to their furthest extent the discoveries attributed by Callimachus in his Iambics to Euphorbus the Phrygian, I mean “scalene triangles” and whatever else has to do with theoretical geometry.)

Thales is also credited with having given excellent advice on political matters. For instance, when Croesus sent to Miletus offering terms of alliance, he frustrated the plan; and this proved the salvation of the city when Cyrus obtained the victory. Heraclides makes Thales himself say that he had always lived in solitude as a private individual and kept aloof from State affairs. Some authorities say that he married and had a son Cybisthus; others that he remained unmarried and adopted his sister’s son, and that when he was asked why he had no children of his own he replied “because he loved children”. The story is told that, when his mother tried to foroe him to marry, he replied it was too soon, and when she pressed him again later in life, he replied that it was too late. Hieronymus of Rhodes in the second book of his Scattered Notes relates that, in order to show how easy it is to grow rich, Thales, foreseeing that it would be a good season for olives, rented all the oil-mills and thus amassed a fortune.

His doctrine was that water is the universal primary substance, and that the world is animate and full of divinities. He is said to have discovered the seasons of the year and divided it into 365 days.

He had no instructor, except that he went to Egypt and spent some time with the priests there. Hieronymus informs us that he measured the height of the pyramids by the shadow they cast, taking the observation at the hour when our shadow is of the same length as ourselves. He lived, as Minyas relates, with Thrasybulus, the tyrant of Miletus.

The well-known story of the tripod found by the fishermen and sent by the people of Miletus to all the Wise Men in succession runs as follows.Certain Ionian youths having purchased of the Milesian fishermen their catch of fish, a dispute arose over the tripod which had formed part of the catch. Finally the Milesians referred the question to Delphi, and the god gave an oracle in this form:


Who shall possess the tripod? Thus replies

Apollo: “Whosoever is most wise”.


Accordingly they give it to Thales, and he to another, and so on till it comes to Solon, who, with the remark that the god was the most wise, sent it off to Delphi. Callimachus in his Iambics has a different version of the story, which he took from Maeandrius of Miletus. It is that Bathycles, an Arcadian, left at his death a bowl with the solemn injunction that it “should be given to him who had done most good by his wisdom”. So it was given to Thales, went the round of all the sages, and came back to Thales again.And he sent it to Apollo at Didyma, with this dedication, according to Callimachus:


Lord of the folk of Neleus' line,

Thales, of Greeks adjudged most wise,

Brings to thy Didymaean shrine

His offering, a twice-won prize.


But the prose inscription is:


Thales the Milesian, son of Examyas [dedicates this] to Delphinian Apollo after twice winning the prize from all the Greeks.


The bowl was carried from place to place by the son of Bathycles, whose name was Thyrion, so it is stated by Eleusis in his work On Achilles, and Alexo the Myndian in the ninth book of his Legends.

But Eudoxus of Cnidos and Euanthes of Miletus agree that a certain man who was a friend of Croesus received from the king a golden goblet in order to bestow it upon the wisest of the Greeks; this man gave it to Thales, and from him it passed to others and so to Chilon.

Chilon laid the question “Who is a wiser man than I?” before the Pythian Apollo, and the god replied “Myson”. Of him we shall have more to say presently. (In the list of the Seven Sages given by EudoxusMyson takes the place of Cleobulus; Plato also includes him by omitting Periander.) The answer of the oracle respecting him was as follows:


Myson of Chen in Oeta; this is he

Who for wiseheartedness surpasseth thee;


and it was given in reply to a question put by AnacharsisDaimachus the Platonist and Clearchus allege that a bowl was sent by Croesus to Pittacus and began the round of the Wise Men from him.

The story told by Andron in his work on The Tripod is that the Argives offered a tripod as a prize of virtue to the wisest of the Greeks; Aristodemus of Sparta was adjudged the winner but retired in favour of Chilon.Aristodemus is mentioned by Alcaeus thus:


Surely no witless word was this of the Spartan, I deem,

“Wealth is the worth of a man; and poverty void of esteem”.


Some relate that a vessel with its freight was sent by Periander to Thrasybulus, tyrant of Miletus, and that, when it was wrecked in Coan waters, the tripod was afterwards found by certain fishermen. However, Phanodicus declares it to have been found in Athenian waters and thence brought to Athens. An assembly was held and it was sent to Bias; for what reason shall be explained in the life of Bias.

There is yet another version, that it was the work of Hephaestus presented by the god to Pelops on his marriage. Thence it passed to Menelaus and was carried off by Paris along with Helen and was thrown by her into the Coan sea, for she said it would be a cause of strife. In process of time certain people of Lebedus, having purchased a catch of fish thereabouts, obtained possession of the tripod, and, quarrelling with the fishermen about it, put in to Cos, and, when they could not settle the dispute, reported the fact to Miletus, their mother-city. The Milesians, when their embassies were disregarded, made war upon Cos; many fell on both sides, and an oracle pronounced that the tripod should be given to the wisest; both parties to the dispute agreed upon Thales. After it had gone the round of the sages, Thales dedicated it to Apollo of Didyma. The oracle which the Coans received was on this wise:


Hephaestus cast the tripod in the sea;

Until it quit the city there will be

No end to strife, until it reach the seer

Whose wisdom makes past, present, future clear.


That of the Milesians beginning “Who shall possess the tripod?” has been quoted above. So much for this version of the story.

Hermippus in his Lives refers to Thales the story which is told by some of Socrates, namely, that he used to say there were three blessings for which he was grateful to Fortune: “first, that I was born a human being and not one of the brutes; next, that I was born a man and not a woman; thirdly, a Greek and not a barbarian”. It is said that once, when he was taken out of doors by an old woman in order that he might observe the stars, he fell into a ditch, and his cry for help drew from the old woman the retort, “How can you expect to know all about the heavens, Thales, when you cannot even see what is just before your feet?”. Timon too knows him as an astronomer, and praises him in the Silli where he says:


Thales among the Seven the sage astronomer.


His writings are said by Lobon of Argos to have run to some two hundred lines. His statue is said to bear this inscription:


Pride of Miletus and Ionian lands,

Wisest astronomer, here Thales stands.


Of songs still sung these verses belong to him:


Many words do not declare an understanding heart.

Seek one sole wisdom.

Choose one sole good.

For thou wilt check the tongues of chatterers prating without end.


Here too are certain current apophthegms assigned to him:


Of all things that are, the most ancient is God, for he is uncreated.

The most beautiful is the universe, for it is God's workmanship.

The greatest is space, for it holds all things.

The swiftest is mind, for it speeds everywhere.

The strongest, necessity, for it masters all.

The wisest, time, for it brings everything to light.


He held there was no difference between life and death.

“Why then”, said one, “do you not die?”

“Because”, said he, “there is no difference”.

To the question which is older, day or night, he replied: “Night is the older by one day”.

 Some one asked him whether a man could hide an evil deed from the gods: “No”, he replied, “nor yet an evil thought”.

To the adulterer who inquired if he should deny the charge upon oath he replied that perjury was no worse than adultery. Being asked what is difficult, he replied, “To know oneself”.

“What is easy?” “To give advice to another”.

 “What is most pleasant?” “Success”.

 “What is the divine?” “That which has neither beginning nor end”.

 To the question what was the strangest thing he had ever seen, his answer was, “An aged tyrant”.

“How can one best bear adversity?” “If he should see his enemies in worse plight”.

“How shall we lead the best and most righteous life?” “By refraining from doing what we blame in others”.

“What man is happy?” “He who has a healthy body, a resourceful mind and a docile nature”.

 He tells us to remember friends, whether present or absent; not to pride ourselves upon outward appearance, but to study to be beautiful in character. “Shun ill-gotten gains”, he says. “Let not idle words prejudice thee against those who have shared thy confidence”. “Whatever provision thou hast made for thy parents, the same must thou expect from thy children”. He explained the overflow of the Nile as due to the etesian winds which, blowing in the contrary direction, drove the waters upstream.

Apollodorus in his Chronology places his birth in the first year of the 35th Olympiad. He died at the age of 78 (or, according to Sosicrates, of 90 years); for he died in the 58th Olympiad, being contemporary with Croesus, whom he undertook to take across the Halys without building a bridge, by diverting the river.

There have lived five other men who bore the name of Thales, as enumerated by Demetrius of Magnesia in his Dictionary of Men of the Same Name:

1. A rhetorician of Callatia, with an affected style.

2. A painter of Sicyon, of great gifts.

3. A contemporary of Hesiod, Homer and Lycurgus, in very early times.

4. A person mentioned by Duris in his work On Painting.

5. An obscure person in more recent times who is mentioned by Dionysius in his Critical Writings.

Thales the Sage died as he was watching an athletic contest from heat, thirst, and the weakness incident to advanced age. And the inscription on his tomb is:


Here in a narrow tomb great Thales lies;

Yet his renown for wisdom reached the skies.


I may also cite one of my own, from my first book, Epigrams in Various Metres:


As Thales watched the games one festal day

The fierce sun smote him, and he passed away;

Zeus, thou didst well to raise him; his dim eyes

Could not from earth behold the starry skies.


To him belongs the proverb “Know thyself”, which Antisthenes in his Successions of Philosophers attributes to PhemonoE, though admitting that it was appropriated by Chilon.

This seems the proper place for a general notice of the Seven Sages, of whom we have such accounts as the following. Damon of Cyrene in his History of the Philosophers carps at all sages, but especially the Seven. Anaximenes remarks that they all applied themselves to poetry; Dicaearchus that they were neither sages nor philosophers, but merely shrewd men with a turn for legislation. Archetimus of Syracuse describes their meeting at the court of Cypselus, on which occasion he himself happened to be present; for which Ephorus substitutes a meeting without Thales at the court of Croesus. Some make them meet at the Pan-Ionian festival, at Corinth, and at Delphi. Their utterances are variously reported, and are attributed now to one now to the other, for instance the following:


Chilon of Lacedaemon’s words are true:

Nothing too much; good comes from measure due.


Nor is there any agreement how the number is made up; for Maeandrius, in place of Cleobulus and Myson, includes Leophantus, son of Gorgiadas, of Lebedus or Ephesus, and Epimenides the Cretan in the list; Plato in his Protagoras admits Myson and leaves out PerianderEphorus substitutes Anacharsis for Myson; others add Pythagoras to the Seven. Dicaearchus hands down four names fully recognized: Thales, Bias, Pittacus and Solon; and appends the names of six others, from whom he selects three: AristodemusPamphylusChilon the Lacedaemonian, CleobulusAnacharsisPeriander. Others add Acusilaus, son of Cabas or Scabras, of Argos.Hermippus in his work On the Sages reckons seventeen, from which number different people make different selections of seven. They are: Solon, Thales, Pittacus, Bias, ChilonMysonCleobulusPerianderAnacharsisAcusilausEpimenidesLeophantusPherecydesAristodemus, Pythagoras, Lasos, son of Charmantides or Sisymbrinus, or, according to Aristoxenus, of Chabrinus, born at Hermione, Anaxagoras. Hippobotus in his List of Philosophers enumerates: Orpheus, Linus, Solon, PerianderAnacharsisCleobulusMyson, Thales, Bias, Pittacus, Epicharmus, Pythagoras.

Here follow the extant letters of Thales.

“Thales to Pherecydes

I hear that you intend to be the first Ionian to expound theology to the Greeks. And perhaps it was a wise decision to make the book common property without taking advice, instead of entrusting it to any particular persons whatsoever, a course which has no advantages. However, if it would give you any pleasure, I am quite willing to discuss the subject of your book with you; and if you bid me come to Syros I will do so. For surely Solon of Athens and I would scarcely be sane if, after having sailed to Crete to pursue our inquiries there, and to Egypt to confer with the priests and astronomers, we hesitated to come to you. For Solon too will come, with your permission.You, however, are so fond of home that you seldom visit Ionia and have no longing to see strangers, but, as I hope, apply yourself to one thing, namely writing, while we, who never write anything, travel all over Hellas and Asia”.

“Thales to Solon

“If you leave Athens, it seems to me that you could most conveniently set up your abode at Miletus, which is an Athenian colony; for there you incur no risk. If you are vexed at the thought that we are governed by a tyrant, hating as you do all absolute rulers, you would at least enjoy the society of your friends. Bias wrote inviting you to Priene; and if you prefer the town of Priene for a residence, I myself will come and live with you”.




On the results of recent calculations on the Eclipse of Thales and Eclipses connected with it.

G B Airy, Esq. F.R.S. Astronomer Royal.

On Friday 4 February 1853

The Lecturer commenced by remarking that he should not have thought the calculations connected with any other eclipse a subject worthy of his audience. The eclipse commonly called that of Thales is however one of extraordinary interest. It refers to a point of time which connects in a remarkable way the history of Asia Minor and the Greek colonies settled there with the history of the great Eastern empires. Its precise date has been for a long time a subject of discussion among the ablest astronomical computers and chronologers. It shows in a remarkable degree the power of astronomy; for it is no small thing that we are able to go back so many centuries and confidently to describe a phenomenon which then occurred, almost to its minutest features. But it shows also the weakness of astronomy. It requires the combination of theory and observation, with a full sense of the possible inaccuracies of both, and with an endeavour by the use of each to correct the failings of the other. It requires general criticism, history, tradition, and a careful examination of geographical and military circumstances. But when all these aids are properly brought to bear upon it, a conclusion is obtained upon which there appears to be no room for further doubt.

In the last century, the computations, or rather the assumptions, of distant eclipses, were extremely vague. The theory of the moon's motion, as applicable to distant eclipses, was imperfect; and it would almost seem that computers, under a sense of this imperfection, felt themselves free to interpret the calculations as loosely as they might find convenient. Eclipses were adopted by them, as corresponding to historical accounts, which did not represent the physical phenomena when visible; some were even taken which occurred before sunrise or after sunset at the places of observation.

The great step made in theory, in reference to these inquiries, was the discovery made by Laplace near the end of the last century, of the secular change in the moon's mean motion in longitude (accompanied by similar changes in the motion of the perigee and the node). In explanation of this, the Lecturer pointed out that the force which acts upon the moon tending to draw it towards the earth is not simply the attraction of the earth, but consists of that attraction diminished by a disturbing force which is produced by the sun's attraction. The sun sometimes attracts the moon towards the earth or the earth towards the moon, sometimes it produces the opposite effect; but on the whole it tends to pull the moon away from the earth. And this diminution of the earth's attraction is greater as the sun is nearer; and therefore, in an elliptic orbit such as the earth describes about the sun (or such as the sun appears to describe about the earth), the diminution of the earth's attraction is greater when the earth is nearest to the sun than when the earth is farthest from the sun. It might be supposed that one of these effects exceeds that which would happen when the earth is at its mean distance from the sun, as much as the other falls short of it; but in reality the excess is greater than the deficiency, and therefore the more eccentric the earth's orbit is, the greater is this disturbing force. So long as these circumstances remain the same, the magnitude of the moon's orbit will not be sensibly altered. But the fact is, that, in consequence of the perturbations produced by the planets, though the earth's mean distance from the sun remains unaltered from age to age, yet the eccentricity of its orbit is diminishing from age to age; the sun's disturbing force is therefore diminishing from age to age: and the real force which acts upon the moon as tending to draw it towards the earth is therefore increasing from age to age; and, from age to age, the moon approaches a little nearer to the earth and performs her revolutions a little quicker. This effect is extremely small. Between one lunation and the next (taken one with another) the moon's distance from the earth is diminished by about 1/14 of an inch; it would seem at first that this could produce no discoverable effect in the moon's motion: but one of the most wonderful things in the application of the laws of mechanics generally, and the law of gravitation in particular (where the magnitude of the force varies with the variation of distance), is, that the effect of a variation of a small fraction of an inch is as certain, in proportion to its magnitude, as that of a thousand miles. Still the effect produced in the moon's apparent motion is very small: in a century it amounts to only ten seconds; an angle which, when expressed in the usual way by the breadth of a known object as seen at a known distance, is less than the angle subtended by the human hand as seen at the distance of a mile. Yet in the course of twenty-four centuries the effect of this becomes so important as, in the case of eclipses, completely to change the face of the heavens; an eclipse might happen in Asia or Africa which, but for this consideration, we might expect to occur at that time in America.

Shortly after the discovery of this secular change, the French lunar tables (Bürg's) were constructed, the first which introduced this element. The late Mr Francis Baily soon made use of these in an investigation of the date of the eclipse of Thales, which deserves to be ranked among the most valuable that has been directed to that subject. The historical account of the eclipse is that the Medes attacked the Lydians, and that a war continued several years, until at length, when the two armies were preparing for battle, the day suddenly became night (an event which Thales is said to have predicted), and both parties were so much alarmed that they made peace at once. Mr Baily in the first place pointed out, from a collation of the beet accounts of total and annular and other partial eclipses, that nothing but a total eclipse could produce such a striking effect and that a total eclipse could do it. Mr Baily afterwards saw the total eclipse of 1842, but he saw it from the window of a house: the Lecturer, who had seen the total eclipses of 1842 and 1851, in each case from the top of a hill and in command of the open country, wished much that Mr Baily could so have seen it, when he could not have failed to be reminded of his former assertions with regard to the eclipse of Thales: the phenomenon in fact is one of the most terrible that man can witness, and no degree of partial eclipses gives any idea of its horror. Mr Baily then, using Bürg's tables, computed all the eclipses which could by possibility be visible in Asia Minor through a period of time exceeding that to which the eclipse of Thales is limited by chronological considerations, and found that only the eclipse of B.C. 610, September 30, could be total; and that the track of its shadow would pass across the mouth of the river Halys. He accordingly fixed upon that as the true date. But he then made a calculation which threw great doubt upon the result. Upon using the same tables to compute the eclipse of Agathocles (to be described shortly) he found that the track of the shadow would be nearly 200 miles in error; and, with a degree of good faith which was characteristic of him, he at once avowed his belief that if the elements of the tables were so altered as to make the eclipse of Agathocles possible, the eclipse of B.C. 610 could no longer be shown to be total in or near Asia Minor. He expressed his confidence however that no other eclipse could, under any possible change of the tables, have been total in Asia Minor. Mr Baily's conduct in this avowal was favourably contrasted with that of a German astronomer, Oltmanns; who, in one paper, using the same tables as Baily, fixed upon the same date as Baily for the eclipse of Thales; and in another paper, after alteration of the elements, showed that the eclipse of Agathocles was possible; but, although he then alluded to his own calculations of the eclipse of Thales, had not the courage to announce that his former conclusions must now be considered to be unfounded.

The Lecturer then proceeded to explain how it happens that there exists such a connection between two eclipses nearly 300 years apart, that the errors of calculation of one can have any influence upon the other. He explained that the moon's orbit is inclined to the sun's apparent orbit round the earth, but not always in the same direction, the line of nodes (or the intersection of the planes of the two orbits) revolving so as to complete a revolution in about 191 years; and that an eclipse of the sun can happen only when the line of nodes is turned nearly towards the sun (as, in other cases. the shadow falls above or below the earth). If for a given day of the year, (when the sun is in one certain position), the moon is in that part of its orbit most nearly in the direction of the sun, the shadow of the moon will fall upon a certain point of the earth; but now if the place of the node be changed, the effect will be that of driving a wedge under the moon, and she will be thrown further north or south, and the shadow upon the earth will be thrown further north or south. Thus the place of the node will define the part of the earth on which the shadow will be thrown; and conversely, a knowledge of the part of the earth on which the shadow is thrown will give information on the place of the node. Thus the alteration of the lunar elements, which is necessary to throw the shadow further north in the eclipse of Agathocles, consists in an alteration of the place of the node (other elements being supposed moderately correct); and this requires an alteration in the annual motion of the node, reckoning backwards from the present time when the position of the node is well known; and applying the same annual correction by the rule of three backwards to the place of the node at an assumed time of the eclipse of Thales, the corrected place of the node at, that time is found, and then the corrected track of the moon's shadow can be found.

Subsequently to the time of the calculations of Baily and Oltmanns, the improvements in astronomy haze been very great. Many advances have been made in theory, and one of the secular changes (that of motion of perigee) has been greatly modified. The Greenwich Lunar Observations from 1750 to 1830 (which are the foundation of Lunar Astronomy) have been completely reduced, on one uniform plan. Improvements have been made in the details of construction, but still greater improvements in the principles, of astronomical instruments. Our knowledge, also, of the geography of the countries to which the eclipses before us have relation, is much more accurate and extensive than it was.

Still there remain causes of uncertainty in the results of any calculations made for such distant periods.

First, in the theory. No person who has not fairly entered into the details of the Lunar Theory can conceive the complexity of the algebraical expressions and the operations which occur in it. Besides the usual chances of error from mistake of figures and mistake of signs, there is the risk of mistake in the selection of some terms to the exclusion of others, and the possibility of positive error in the metaphysical reasoning which guides some of the operations. And we are driven at last to admit that what is sometimes called mathematical evidence is after all but moral evidence. And thus it has happened that the conclusions of different theorists on some very important points are by no means accordant.

Secondly, in the observations from which are determined the elements that are to be combined with theory. Upon the same principle by which it was shown that the track of shadow in one eclipse depends upon the track of shadow in another eclipse, it will be easily seen that the track of shadow in a distant eclipse will depend upon the observed elevation of the moon in the beginning of the modem period of comparatively accurate astronomy; (for that elevation determines the place of the node; and an error in the elevation produces an error in the computed place of the node for that time; and this exhibits an error in the annual motion of the node; and that error carried through the long period to a distant eclipse produces a very great error in the place of the node there, and consequently in the track of the shadow). If a ladder of centuries- be constructed, each stave corresponding to a century, the extent of tolerably accurate and well-reduced observations of the moon (1750 to 1830) is represented by only 4 of an interval of staves. Thus it appears that an error of two seconds in Bradley's observations, (the angle which a finger-ring subtends at the distance of a mile, and which is smaller than can be perceived by the unassisted eye) would destroy our conclusions with regard to the distant eclipses in question. The fault in the principle of the Greenwich instrument used for observing the elevation of the moon (namely a quadrant, the use of which was for many years the bane of astronomy), and the slovenly way of using it in Bradley's time (no attention being given to the taking the elevation of the moon at the precise instant of her passing the meridian, though her elevation then changes rapidly) might well allow of this error. The Lecturer stated that both in the careful examination of the principles on which instruments are constructed, and in the rigorous attention to the proper rules for their use, it might be hoped that great improvement would be found in modem times.

In consequence of these causes of uncertainty, it becomes very desirable, in the investigation of the eclipse of Thales, to correct the elements of the moon's motions by some other well determined eclipse. Omitting the eclipses since the year 1200 A.D., and two in the second century B.C. which are somewhat discordant, there are two eclipses of peculiar value. One is the eclipse at the battle of Stiklastad at which Olaf king of Norway was killed, A.D 1030 August 31; in which the precise spot is known, and the precise position of the moon is known (the breadth of the shadow being very small, inasmuch as, when the eclipse commenced on the earth, it was annular). The only objection is, that if there is any uncertainty in the secular change of mean motions, the adjustment of the mean motions to represent the eclipse of Stiklastad will still leave a large uncertainty on an eclipse about 1600 years before it. Using the illustration of the ladder of centuries, it is like fixing the ladder at the bottom and at a point at one third of its height, which fastening, if the ladder is bent in some uncertain degree, still leaves great uncertainty in the place of its top. The other eclipse is that of Agathocles, B.C. 310, August 15, which will leave little uncertainty of that kind, if we can but determine its exact place upon the earth.

Agathocles, the Lecturer stated, being blockaded by the Carthaginians in Syracuse, placed men on board a fleet, ready to escape on the first opportunity; the approach of a provision-fleet drew off the Carthaginian ships, and Agathocles burst out of the harbour, and was pursued by the Carthaginians, but escaped. The next morning there was an eclipse of the sun which was evidently total. After six days he landed in the Carthaginian territories at a place called the Quarries, and, traversing their provinces, reduced the citizens of Carthage to the utmost difficulty, (in their terror they sacrificed 500 children to their god Kronos). The Lecturer acknowledged his obligations to Capt W H Smyth, R.N. who had called his attention to the enormous quarries at Alhowareah (Aquilaria) under Cape Bon, from which Utica and Carthage were built; which place appears to have been used by the Romans as a landing-place from Sicily; and which the Lecturer adopted without doubt as the landing-place of Agathocles. He then stated that from J W Bosanquet Esq., he had received the suggestion that Agathocles might have passed the Strait of Messina; and that gentleman had pointed out the passages in the historical accounts which indicated the belief of the sailors that they were going either to Italy or to Sardinia. The Lecturer stated that, on minute examination, he had found that only the city of Gela remained in alliance with Syracuse, and the provision-fleet must have come from Gela, and must have approached Syracuse from the south, and from this it followed that Agathocles must have escaped to the north. This brings the probable position of Agathocles at the time of the eclipse near to Messina; if it were still supposed (as had been formerly supposed) that be sailed to the south, his position would probably have been near to Cape Passaro. The Lecturer explained the small corrections which must be made in the Greenwich determination of the place of the moon's node to satisfy these two conditions: and these were then taken as bases for the investigations connected with the eclipse of Thales.

The armies which were confronted at the time of the eclipse of Thales were evidently large armies (from the circumstances that they were commanded by the kings in person, who were ready to make a treaty on the spot, and that their principal allies, Syennesis and Labynetus, were present). And the principal question to be answered is, where such armies were likely to march. The Lecturer called attention to the general form of Mount Taurus and Anti-taurus (as one part is sometimes called), ranging from the mountains in the south of Asia Minor, in a general north-eastern direction, till they joined the mountains about Trebizond and Erzerum; and stated that, according to the best information that he could obtain, (in which he had been materially assisted by W J Hamilton, Esq. and M Pierre Tchihacheff) the following were the principal roads through them. On the north coast there is one, of which the difficulties were well known from the retreat of the ten thousand Greeks. From Erzerum there are two roads towards Siwah (Sebaste) and Kaisarieh (the Cappadocian Caesarea), rugged, and passing through barren countries. There is one road from Kaisarieh falling on a branch of the Euphrates, which flows by Malatieh (Melitene); a rugged road parallel to it from Guroun; and finally, the road which is the best of all, descending from the southern mountains into the plain of Tarsus and Adana, then skirting the sea by Issus to Antioch. The Lecturer stated that on examining history he found no instance of an easterly or westerly march through the northern mountains: he had found one march of an army (under the Byzantine emperor Heraclius) from Trebizond to the south, which army however returned by Issus: one march by Melitene, where the last great battle of Chosroes Nushirvan with the Byzantine armies was fought: but, from the time of the younger Cyrus and Alexander, the marches by Issus are very numerous. Some of these lines of march are evidently very much curved out of their straight direction in order to take advantage of the pass of Issus: thus Alexander marched thither from Angora (Ancyra): Valerian entered by Issus to attack Sapor: Sapor, when in Armenia, and on his way to attack Caesarea, marched by Issus: Julian in return invaded Persia by the same road. From these circumstances it appeared most probable that the Medes entered by Issus to attack the Lydians, and that the battle-field would probably be included in the polygon whose angles are Issus, Melitene, Ancyra, Sardes, and Iconium.

The Lecturer then showed what would be the track of the shadow in the eclipse of B.C. 585, May 28, either on the supposition that the place of the Moon's node was that given by the Greenwich observations, or on the supposition that the motion of the node was so corrected as to make the shadow in the eclipse of Agathocles pass centrally over the assumed southern position of Agathocles, Or over the assumed northern position of Agathocles. The uncorrected Greenwich track, and the track over Asia Minor corresponding to a central eclipse on the southern position of Agathocles, though not inadmissible, are too far south to be accepted as probable; but the track over Asia Minor, corresponding to the elements which give a central or nearly central eclipse for the northern position of Agathocles (near the strait of Messina), would certainly pass over any probable position of the battle-field.

The conclusion as to the general fitness of the eclipse of B.C. 585 for representing the circumstances of the eclipse of Thales, by inference from modern elements of calculation, was first published by Mr Hind in the Athenaeum.

The Lecturer then stated that he had examined in greater or less detail every eclipse from B.C. 630 to B.C. 580, and that no other eclipse could pass over Asia Minor. That selected by Messrs Baily and Oltmanns, it was now shown, passed to the north of the sea of Azof.

In concluding this astronomical discussion, the Lecturer expressed his opinion that the date B C. 585 was now established for the eclipse of Thales beyond the possibility of a doubt.

The Lecturer then alluded to the tradition preserved by Sir John Malcolm from the poetical History of Persia, that Kai Kaoos (whom Sir John Malcolm considers to be the same as Cyaxares or Astyages, or possibly to represent both), having marched on a military expedition into Mazenderam, himself and his army were struck with sudden blindness; and that this had been foretold by a magician. Sir John Malcolm considered, and it appears most probable, that this is the record of a total eclipse of the sun; but no total eclipse near this time passed over Mazenderam. The Lecturer conceived therefore that it might refer to the eclipse of Thales, though with a strange perversion of the name of the province. Such perversions however occur in the Persian poetical history with regard to other names, which there is reason to believe are correctly given by the Greeks. The name Xerxes, for instance, has been found by Colonel Rawlinson in the Behistun inscriptions under the form Khshayarsha, of which the Greek Xerxes was probably a fair oral representation; whereas the name preserved in the poetical history is Isfundear. These confusions however are incidental to poetical history: thus if the Henriade of Voltaire should remain as the only history of the times to which it relates, the name of the king who preceded Henri IV would go down as Valois, instead of Henri III.

[G. B. A.]