Episode 9: Thales, through a Glass Darkly

September 21, 2021

Thales was the first of the Greek astronomers and became known as one of the Seven Sages of Greece. Over the centuries many astronomical discoveries were attributed to him, but what was the reality and what was the hyperbole?


Good evening, and welcome to the Song of Urania, a podcast about the history of astronomy from antiquity to the present with new episodes every full moon. My name is Joe Antognini. In the last two episodes we’ve been introduced to what we might call the folk astronomy of the ancient Greeks. We looked at how they interpreted the heavens through the lens of mythology. And we saw how the implicit cosmological and astronomical ideas of the Greeks made their way into the works of Homer and Hesiod.

But now, and for the foreseeable future, the character of the astronomy we’ll be looking at will change from what we’ve seen in the past eight episodes of this podcast. The history of astronomy as I will be telling it, will change from a history in broad strokes, a history of the astronomy of civilizations and empires, evolving slowly over the centuries, to a personalized kind of astronomy. I’ve mentioned only a few astronomers by name in the narrative up until this point: Berossus and Kidinnu in particular. And many of the astronomical diaries of the Babylonians were signed by the astronomers who wrote them. But it isn’t clear what those particular astronomers contributed to the development of their field, if anything. And in the last episode I talked about Hesiod and Homer, but they were not astronomers and did not develop any new astronomical ideas or techniques themselves. They were poets who happened to convey the astronomical ideas floating about in their culture in their poetry.

But starting with Thales of Miletus, we for the first time can finally start to see the contributions of individual astronomers to the field of astronomy. From time to time I will try to zoom out a little bit and describe the evolution of astronomical thought in Greece and elsewhere in broader strokes. But at least until we finish with ancient Greece, we at long last have the luxury of knowing who it was who developed the astronomy of the culture. At least to an extent. In this episode we’ll be focusing on the first known Greek astronomer, Thales of Miletus. But as we’ll see, even though we know the name Thales and that he came from the city of Miletus on the western coast of Anatolia, and that he lived from sometime around the late 600s to the mid 500s BC, and we know that this man was considered to be a great astronomer, beyond that we unfortunately have very little solid evidence to go on as to what specifically he believed and discovered, and this was true of all of the earliest Greek scientists. Now, I don’t want to downplay this. Having very little solid evidence still means you have a great deal more solid evidence than absolutely no solid evidence or no evidence whatsoever, solid or otherwise, which is all we have to go on prior to this. Nevertheless, I do want to set some realistic expectations here for how completely we can really understand the science of these earliest Greek figures whose names we know.

So before I go ahead and tell you what Thales of Miletus was said to have done and thought, and before I tell you what he may have actually discovered and thought, it would be wise to ask ourselves how we know what we know about ancient Greek astronomy and the earliest Greek astronomers. Now, Greece was a relatively literate society by the standards of the ancient world. In many of the other great civilizations of the ancient world that developed a system of writing, the Egyptians, Babylonians, Chinese, literacy was largely confined to a small class of priests and scribes. But Greece never developed a specialized class of scribes, perhaps because of the highly decentralized nature of its politics. The earlier Mycenaeans had developed a system of writing known today as Linear A and Linear B, but records in Linear B stop after the Late Bronze Age Collapse, and apparently literacy in the region declined during the Greek Dark Ages. But as the ancient near east began to recover from the Late Bronze Age Collapse, the nearby growing civilization of the Phoenicians came up with an interesting innovation. Rather than a hieroglyphic or pictographic system like the Egyptians and Chinese, where each word has a unique character associated with it, and unlike the cuneiform of the Babylonians and Assyrians, or the earlier Linear B script of the Mycenaeans, where each character represented either a word or a syllable, the writing that the Phoenicians developed was a true alphabet, where each symbol represented a particular phoneme. This innovation was to become extremely popular because it was enormously flexible. Characters tied to individual words and syllables were closely tied to the original language that they were developed for.

Now, this doesn’t mean that you can’t adopt a logographic script from one language to another. In fact the Japanese did just that with Chinese logograms and still use them today in what is called Kanji. Today kanji tends to be used mostly for what are called “content words,” things that tend to be more concrete in meaning, rather than function words, which are used more for syntactical purposes and tend to vary much more widely between languages. Content words can oftentimes translate relatively more or less directly between languages but this is much more difficult for function words. Consequently, it’s easier to adopt a logographic system from another language for your content words, but a lot harder to do that for your function words. So Japanese writing today uses kanji, the Chinese logographs, for their content words, and falls back on a separate writing system which is syllabic, called Kana, for the function words.

Well, of course millions of people today can read Japanese, but because of its origins as a borrowed logographic script, Japanese orthography is notorious for its complexity. By contrast, if the characters of your script simply represent phonemes, that is, individual consonants and vowels, the script can translate relatively easily from one language to another. It doesn’t matter what the content or meaning of the word is, all you need to do is sound it out, and write down the sounds. Now, you can run into some problems if your language has sounds that the first language doesn’t. But this issue can be circumvented fairly easily just by switching around the sounds associated with the various characters, or adding a new character or two to represent the new sounds. Once you’ve hit upon the basic idea that each character represents a sound, making some tweaks here and there isn’t all that hard by comparison.

Now, to be clear, the Phoenician script did not develop in a vacuum here. It evolved from an earlier Proto-Sinaitic script from the late Bronze age and also actually incorporated some elements from Egyptian hieroglyphs along the way. As I mentioned last episode, the Phoenicians were a thalassocratic civilization and developed an extensive trading network across the Mediterranean. In fact, centuries later, one of their major settlements, Carthage, eventually became a major nuisance for the Romans as the Romans started embarking on their quest for world domination. All this is to say that the Phoenicians contacted many civilizations across the Mediterranean and many of these civilizations encountered Phoenician writing and saw its advantages. The Greeks were one of these. In fact, both the Greek script and our modern day Latin script derive from the Phoenician alphabet.

Writing in Greece starts to be reintroduced into the historical record in the early 8th century BC in the form of graffiti on pottery at gravesites, probably from relatives inscribing either the name of the deceased or their own names. Because the vases and pots were sealed in the tomb, the date of the writing can be established as being roughly contemporaneous with the date that the pottery was made and Greek pottery can be reliably dated based on the artistic style. How did archaeologists figure out the dates of the various artistic styles in the first place? A rough chronological order can be determined at certain sites based on relative depths in the soil. But the more conclusive evidence is if there happens to be organic remains near the pottery like bones or charcoal, in which case radiocarbon dating can be used to get a date perhaps to within a few decades. It only takes a relatively small number of archaeological sites that happen to have the necessary organic material together with the pottery in order to tie distinct artistic and technical styles to different eras.

Well, it seems that writing was present in Greece relatively early on in the archaic period, but its use was fairly limited, at least based on the records we have available to us. The writing we see is almost entirely names scratched onto funerary vases, though there are two notable exceptions. There is a wine jug called an oenochoe dating from around 740 BC that has an inscription in hexametric verse, “Whoever of all the dancers now dances most daintily, of him this…” and then the text becomes unclear but maybe reads pot. Then there is an artifact known as “Nestor’s cup”, which is a wine cup called a skyphos from perhaps the late 700s with a three line inscription that reads:

I am the cup of Nestor good for drinking. Whoever drinks from this cup, desire for beautifully crowned Aphrodite will seize him instantly.

But given the paucity of written records from the early archaic period, especially compared to the more detailed records we have in Linear B from the Mycenaean civilization, it is clear that literacy was not widespread in Archaic Greece and the society was predominantly oral. In fact there is only a single reference to writing in The Iliad in Book 6, in which Homer takes a small digression, much like this podcast is wont to do, and tells a small story about the hero Bellerophon, who you may remember from Episode 6 as being the true companion of the winged horse Pegasus. Well, in Homer’s telling, Bellerophon happened to be in Tiryns, where Proetus was king. The queen Anteia fell in love with Bellerophon and made advances on him, but Bellerophon kept his honor and rebuffed her. Then — well, why should I tell this story, let’s let Homer do it:

That strong king Proetus
now drove Bellerophon out of Argos
this because Anteia, the queen,
lusted to couple with him secretly,
but he was honorable, she could not lure him,
and in the king’s ear hissed a lie: ‘Oh Proetus
I wish that you may die unless you kill
Bellerophon — he desired to take me
in lust against my will.’ Rage filled the king
over her slander, but being scrupulous
he shrank from killing him. So into Lykia
he sent him, charged to bear a deadly cipher,
magical marks Proitos engraved and hid
in folded tablets. He commanded him
to show these to his father-in-law,
thinking in this way he should meet his end.
Guided by gods he sailed, and came to Lykia,
high country, crossed by Xanthos’s running stream;
and Lykia’s lord received him well.
Nine days he honored him, nine revels led
with consecrated beasts. When Dawn was rosy
fingers eastward made the tenth day bright,
he questioned him, and asked at length to see
what sign he brought him from his son-in-law.
When he had read the deadly cipher, changing,
he gave his first command: his guest should fight
and quell a foaming monster, the Chimera,
of ghastly and inhuman origin,
her forepart lionish, her tail a snake’s
a she-goat in between.

So the king Proitus wanted to kill Bellerophon for supposedly having attempted to rape his wife, but Proitus couldn’t do this himself because Bellerophon was his guest, and to kill a guest was to invite the wrath of the furies. So he had written a coded letter to his father-in-law telling him that Bellerophon had attempted to rape his wife, or his father-in-law’s daughter, and had Bellerophon transport the letter, expecting that his father-in-law would execute the man. But his father-in-law received Bellerophon as a guest before he read the letter and so couldn’t kill Bellerophon without inviting the wrath of the furies as well. So instead he attempted to kill the hero the way that most kings tried to kill seemingly invincible heroes — he sent him on what he believed to be an impossible quest to kill a terrifying monster. At any rate, the interesting bit here is that Homer describes the writing as “magical marks”, or in another translation, “baneful signs”, which seems to indicate that writing was very rare at the time and held special significance.

Well, based on the available archaeological evidence, it seems that writing spread slowly throughout Greece during the Archaic period. By around 600 BC, around the time when Thales of Miletus was coming of age it is estimated that the number of literate men in the larger cities may have numbered in the hundreds, and that more modestly sized Greek cities may have had a few dozen literate men. We have less evidence as to the number of literate women, but it was certainly considerably smaller, although literate women were not unheard of, the poetess Sappho being a principal example. But Sappho was born to a very wealthy family and was exceptional in many ways, not simply on account of her literacy.

At any rate, during the sixth century, literacy seems to have spread more rapidly throughout Greece. By the middle of the 6th century, the philosopher Pherecydes had developed a new cosmogony and wrote it down in a text called Pentemychos, meaning the five recesses. The cosmogony itself is still highly mythological in character, but what is notable about the text is that Pherecydes wrote it down in prose rather than verse. This is one of the early indications that written text was starting to take primacy over oral transmission in Greek civilization.

This isn’t the only evidence of this, either. Particularly in the later half of the 6th century BC as tyrannies began to wane in favor of nascent forms of democracy, cities began to inscribe their laws in public places. Of course, it was certainly not the case that everyone could read those inscriptions, or even that most people could, but it does suggest that there was a large enough literate population to make it worth their while. And more fundamentally it again established the primacy of written text over oral transmission.

One of the later Athenian tyrants was a man by the name of Hipparchus, not to be confused with the astronomer named Hipparchus from the second century BC whom we’ll talk about in a future episode. Hipparchus constructed a series of monuments called herms along the roads in the countryside leading to Athens. A herm is a kind of interesting piece of sculpture. It’s a square pillar, about human height, with a bust of a head on top, oftentimes depicting the god Hermes. Then, somewhat inexplicably, at least to modern viewers, there is also a model of male genitalia stuck on at the appropriate height. Herms were usually placed to mark boundaries and along roads, particularly at crossroads. Hipparchus also added some engravings to his herms describing how they came to be by saying, “This is a monument of Hipparchus,” and then giving a bit of advice to the traveller like, “Do not deceive a friend.” Most people who encountered these herms probably could not learn that Hipparchus had erected the herm and came away no wiser and continued to deceive their friends, but Hipparchus must have thought that enough of the population could read the engraving, or knew someone who could, to go to the trouble of adding the engravings to ensure that they didn’t forget who it was that was in charge.

By the end of the sixth century literacy must have been quite widespread, though nevertheless still very far from universal. By this point, for example, Athens had adopted a democratic procedure called ostracism. Once a year, the citizens were permitted to vote as to whether they would ostracize one of the citizens of the city. If the vote passed, they would return two months later to then vote on which citizen in particular, was to be ostracized. The unlucky man was forced into exile for a duration of 10 years. According to Plutarch, a quorum of 6000 votes was required for the ostracism to be valid, and votes were written onto potsherds, or broken pieces of pottery. Now, this does not necessarily imply that Athens had at least 6000 literate men. There were probably scribes who would write down the votes of the illiterate population. But it does imply that by this point writing had begun to occupy a central role in the legal, political, and cultural life of the ancient Greeks.

I have already mentioned the philosopher Pherecydes, who wrote his cosmogony in prose, perhaps in the middle of the 6th century, but as the 6th century progressed, other philosophers began writing their ideas down as well. Prior to Pherecydes, in the early 6th century, another natural philosopher named Anaximander, who was possibly a student of Thale’s wrote his ideas down in a work called, simply enough, On Nature. Now, unlike Pherecydes, Anaximander wrote his ideas down in verse, so Pherecydes gets the distinction of having written the first philosophical text in prose, but the point is that it’s around this time that philosophers start putting their ideas into text and this practice only grows throughout antiquity. We’ll have a lot more to say about Anaximander in the next episode, but Thales just missed the mark here. As far as we know, Thales never wrote any treatises. He probably was literate and wrote letters to his contemporaries, but these haven’t survived except two highly dubious quotations in a much later source. Although writing was growing in ancient Greece at the time, it was still primarily an oral intellectual culture. So you might suppose that this really puts us out of luck in terms of understanding what he thought. But in some ways this doesn’t actually end up mattering a great deal. Our knowledge of Thales is not all that different from the other early Greek philosophers who did write down their ideas for posterity.

Unfortunately, sometime between the time these other early Greek philosophers wrote their thoughts down and today, all copies of these texts were lost, either destroyed intentionally, unintentionally, by fire or neglect. However, the Greeks, being a highly literate culture, did not produce works in a vacuum. Their texts referred to other texts, taking ideas from them and explaining why they were wrong and why this other idea was better, or just compiling together the ideas from a whole bunch of people into a single work. So a number of later texts either copied passages from these earlier works, or paraphrased the ideas to make various points. Unfortunately, all these texts have been lost as well. However, even later texts cited, plagiarised, and otherwise referenced these intermediate works, and some of these texts survived to modernity. And this is the essential problem of understanding the early Greek philosophers. We’re oftentimes not looking at the text itself, nor are we looking at an intermediate’s interpretation of the text, but we’re looking at the text two or three times removed. Each chain in the copy potentially adds its own ideas, biases, or mistakes, which makes it sometimes very hard to divine what the original thinker actually thought. But this doesn’t mean we can’t try.

An important way that the ideas of the older philosophers persisted was through a kind of text called an epitome. An epitome was a sort of ancient version of the Reader’s Digest or Cliff Notes and is where we get the modern meaning of the word epitome as being the distilled essence of something. An epitome was a collection of short summaries of the thoughts of various philosophers for the thinking man on the go. But usually these summaries would be written by a new author rather than quoting from the original philosophers, so the accuracy of the epitome depends on the skill of the later author. Related to this is a type of text called a doxography. Unlike an epitome, which was a standalone work, a doxography can simply be a passage from some other work that happens to describe the ideas of an earlier philosopher. Plato and Aristotle both included a number of doxographies in their works in order to present the ideas of an earlier philosopher so that they could then demonstrate why those ideas were wrong and their own proposed ideas were correct. Plato, in particular, seems to have done a relatively good job at fairly representing the views of earlier philosophers, perhaps because he structures his texts as dialogues, with Socrates conversing with another philosopher. Since the philosopher is given the chance to speak for himself, he can present his argument in the strongest possible terms. Aristotle is not quite so fair. Although he wrote many more doxographies, and as a general practice introduced his topics by providing a sort of historical overview of the thoughts of earlier philosophers as a sort of ancient Greek version of a literature review, it seems as though he had a tendency to misrepresent the views of those earlier philosophers in order to make a particular point. As we’ll talk about in a later episode, the works of Aristotle are notoriously difficult to read, probably because they were not meant to be standalone texts, but may have been more like lecture notes.

Now, one of the most important doxographies was a written by a student of Aristotle called Theophrastus, whose name was given to him by Aristotle himself and meant “divinely phrased” for the quality of his writings. For our purposes, the most important of his writings was a text that has been variously called The History of Physics or Physical Opinions, or Opinions of the Natural Philosophers, or Opinions in Natural Philosophy. As you might guess by the fact that we don’t actually know the title of this work, it was lost to history and only a few fragments of text survive. This is a tragedy because it was by all accounts a remarkably thorough and fair exposition of the ideas of the early Greek philosophers. But thanks to its high quality it managed it survive through the end of antiquity in broad form because later writers used it as their primary source for their own histories of early Greek natural philosophy. In fact, one of the later texts follows Theophrastus so closely that we can actually reconstruct exactly what chapters were in the original work. This is the text called the Refutation of All Heresies written by St. Hippolytus of Rome. As his name suggests this was written quite a bit later than Theophrastus’s original text. Theophrastus was active around the late 4th century and early 3rd century BC, and St. Hippolytus was active in the early 3rd century AD, by which point Christianity had started to spread through the Greek world. St. Hippolytus was interested in, well, refuting all heresies, just as it says on the tin. But in order to do so, he had to do the work of explaining exactly what the heretics thought so that he could explain why they were wrong. St. Hippolytus cast himself a very broad net here. He did not limit himself to what we normally think of as heresies, namely Christian sects that the Catholic Church considered heretical (and I’m also including the Orthodox Church there because the two were united at that time). He did, of course, refute a number of these, like the Gnostic heresy, which itself was a very broad movement with a variety of branches, but more or less centered around an idea that Jesus Christ had imparted some hidden knowledge to some of his disciples and that an individual’s spiritual task was to escape their irredeemably corrupt earthly bodies into the realm of the divine. And he covered the heresy of docetism, which is an idea that Jesus Christ was a sort of divine ghost or apparition and never took on human flesh as a physical being, and a heresy propounded by Noetus of what is called modalistic monarchianism, which would require probably half a year’s worth of podcast episodes just to lay the foundations of trinitarian theology and Christology to understand what exactly that’s even talking about.

But St. Hippolytus spent most of his time refuting other ideas that we wouldn’t exactly call heretical today, just not Christian. He writes about various branches of Judaism of the time, the Pharisees, the Sadducees, the Essenes, though by the time he was writing the latter two groups were on their way out, he writes about the Chaldeans over in Babylon, the Brahmins of India, the Celtic druids, he writes about magicians and astrologers, and most relevant to us, he writes extensively about the early Greek philosophers.

When St. Hippolytus first embarked on this project, it seems he had a limited number of sources available to him and wrote the first part of the text based around those, but at some point he came into a copy of Theophrastus’s text and could write a more detailed description of the thoughts of many Greek philosophers.

Now, I don’t want to imply that the Refutation of All Heresies of St. Hippolytus is the only surviving text that we have to understand the ideas of the early Greek natural philosophers. It is an especially complete text, which is why I dwelled on it for some time, but certainly not the only one, and, of course, it itself derives from a number of other texts, some surviving, some not. There is also a work called De Placita Philosophorum, by a philosopher named Aëtius, which doesn’t survive and was probably drawn from an even older text which has been given the name Vestusta Placita, which also didn’t survive, and was in turn drawn from Theophrastus. But, Aetius’s work heavily influenced another work called Placita Philosophorum written by an author who called themselves Plutarch, but wasn’t actually the famous Plutarch, but some unknown author who just palmed his works off as Plutarch’s in order to attract more attention. But it seems to have worked as the work of this author, today called Pseudo-Plutarch, survives. So you can see that there was considerable variety in the quality of ancient sources, and some of the sources we have available to us today are as many as four times removed from the original work of Theophrastus.

This strain of texts that I’ve been describing generally originates with Theophrastus and is primarily interested in describing the ideas of the various natural philosophers. But there is another strain of works that survive to this day and these are more biographical in nature. The ur-text in this strain is a text called Successions by the philosopher Sotion of Alexandria. Like the work of Theophrastus, this doesn’t survive, but was an important source for later authors. Sotion’s text apparently discussed a number of notable philosophers, but was also interested in their lives as well as their ideas. I won’t go through the whole litany of all the later texts that drew from Sotion or the other independent strains of biographical works, but one of the more important works that drew from Sotion was a text called The Lives and Opinions of Eminent Philosophers by a man named Diogenes Laërtius. This work is mostly important because it survived and few of the other biographical works did. But it is a frustrating text for modern scholars because while it represents the only surviving work in a particular strain of literature, by all accounts Diogenes Laërtius had no idea what he was doing. As the historian John Dreyer puts it, “he was more interested in trivial anecdotes than in the doctrines of the philosophers.” Dreyer goes on to say that his work “is a very carelessly made compilation by an author who does not always appear to understand what he is writing about.” John Dreyer was not alone in this viewpoint. The historian Thomas Heath writes that his book “is a compilation made in a most haphazard way, without the exercise of any historical sense or critical faculty.” Nevertheless, for many topics, Diogenes Laertius’s work, as unfortunate as it is, is all we have to go on.

Well, all this exposition is to say that when we’re trying to understand what Thales and other early Greek philosophers thought, we do need to be very careful, because we’re looking through a glass darkly. All those caveats out of the way, what is it, exactly that the later sources say that Thales thought? As it turns out, a great deal. Thales was hugely influential in ancient Greece and only became more so over time. In the same way that in the 20th century, Einstein became an icon of the genius scientist, and if you were alive in the 19th century, Newton would have been the name you would immediately reach to if someone asked you to name the smartest person. And more generally it seems that every era has needed someone to fill this role and ancient Greece was no exception. For them, it was Thales. Consequently, later writers attributed all sorts of discoveries and tales to him simply because he was regarded as the quintessential genius.

This earned Thales a place among the famed Seven Sages of Greece. These were seven men who were exalted in the Greek culture for their wisdom. Interestingly, though, only Thales could really be considered a philosopher in the modern sense of the word. The other six were influential statesmen. There is actually no canonical list of who the seven were, but always included among them were Solon of Athens, who was highly influential in the development of democracy in Athens, and Chilon of Sparta, who was influential in the development of the militaristic Spartan culture. Another sage, Pittacus of Mytilene was influential in helping to bring the aristocracy under control. Since he couldn’t directly single the aristocracy out, he did this in a clever way. As ruler of Mytilene he introduced a law that imposed a double punishment on anyone who violated a law while drunk. The aristocrats were far more frequently intoxicated than the commoners, so this had the effect of helping to rein in their behavior.

The Seven Sages of Greece had evidently permeated the cultural consciousness of the classical Mediterranean. Although all of the sages lived during the 6th century BC, they were remembered in a semi-mythical manner many centuries later. Some 600 years later off to the west in Rome there is a unique piece of archaeological evidence for the extent of their influence. There was a small town about 15 miles southwest of the city of Rome called Ostia Antica that the Romans had constructed, originally as a military camp, but which later grew into a town in its own right. At some point, perhaps during the 1st century AD, the Romans built out a number of amenities in the town, and among them was a public latrine. Now, latrines in ancient Rome were rather different than the latrines of today. The Romans were less squeamish about privacy while answering the call of nature than we moderners are. The construction of the latrine was a square room with a stone bench along the four walls with holes in the bench every few feet or so, with no dividers between the holes. You simply did your business in full view of everyone else in the room. Now, historians believe that the Romans would probably cover their lower half with a sheet of cloth, but nevertheless, going to the public latrine was apparently something of a social activity and people would talk and joke with each other. So that is certainly quite different from the public latrines we are used to. But one thing ancient latrines had in common with the public latrines of today was that just as we do, the Romans delighted in writing graffiti on the walls, especially graffiti of a scatological nature. Here, of all places, in the public latrine of the town of Ostia Antica, hundreds of miles away from Greece and centuries later, we find references to the Seven Sages of Greece.

One of the graffiti says “Ut bene cacaret, ventrum palpavit Solon”, which translates to “To poop well, Solon rubbed his belly.” Now, as a note here, when I began this podcast, I was under the impression that a podcast about the history of astronomy would have no content of an explicit nature and labeled my podcast as clean. At that time, however, I will admit that I was not aware of the graffiti in the public latrine of Ostia Antica. Nevertheless, I will honor my original pledge that this is a clean podcast and translate this with the word “poop”. But if you are a mature individual over the age of 18, you may feel free to substitute another word for “poop” if you so desire.

Another graffito references the subject of this episode, Thales: “Durum cacantes monuit ut nitant Thales”, which translates to “Thales admonished those pooping to strain hard.” And Chilon of Sparta provides some advice as well: “Vissire tacite Chilon docuit subdolus”, which translates to “Sly Chilon taught to fart silently.”

The sages are not the only ones to provide advice to the occupants of the latrine. Another graffito recommends, “shake yourself about so you’ll go faster.” Another seems to poo-poo the practice of giving advice entirely and reads, “friend, the proverb escapes you, poop well and screw the doctors.” Feel free here, to substitute another word for “screw.” The implication of the proverb escaping you is that proverbs are crap. Finally, there is a rather more personal graffito, “no one talks to you much, Priscianus, until you use the sponge on a stick.” We don’t know anything about this Priscianus, but, to be honest, it is impressive that the name of this otherwise anonymous man has survived some two thousand years, even if it is only as some graffiti scrawled in a public bathroom. While I hope that this podcast will echo down the centuries, realistically the name of Priscianus will likely last longer than my own. Now, this doesn’t come across in the English, but in the Latin, the sayings attributed to the Seven Sages are in a more formal register than those that aren’t attributed to anyone at all. The advice of the sages on how to have a satisfying bowel movement is written in the past tense, in the third person, and in the meter of iambic senarii, which was commonly used in Roman comedies. By contrast, the other graffiti is written in a common register: first and second person, present tense, and without any particular meter.

One other detail to note about this last graffito “No one talks to you much, Priscianus, until you use the sponge on a stick” is the sponge on the stick, or a xylospongium. The ancient Romans did not have toilet paper so they used the xylospongium to clean themselves after they did their business instead. This was a stick with a sea sponge attached to one end. This was not exactly a disposable instrument and so was shared by everyone who used the latrine. Of course the Romans were not barbarians and had some sense of hygiene and would keep a bucket filled with vinegar to clean it between uses.

Now, if you’ve read the Gospel of John, you may remember that as Jesus is dying on the cross, he says he is thirsty and a Roman centurion attaches a sponge to a stick and offers vinegar to Jesus. The implication of this is lost on most modern readers because it seems like kind of a strange thing to do, but to someone living in the ancient world, everyone knew what a sponge on a stick soaked in vinegar was used for. The centurion was essentially offering a toilet brush to taunt a thirsty convict dying on the cross. Or that is one interpretation anyway. In the gospels of Mark and Matthew there is a different story, where Jesus is offered wine mixed with either myrrh or gall and the interpretation here is that these had a sedative effect and were offered by the Romans as an act of mercy. But to be honest, while I’ve frequently seen this explanation, I’ve seen little independent evidence that this was a common practice in ancient Rome. Roman soldiers were not especially known for their works of mercy. But as is so frequently the case, I am straying off topic.

Well let’s get back to Thales. The whole point of all that was that Thales was broadly perceived as the paradigmatic wise man, to the point that commoners in Rome were graffitiing his name in public latrines in a different country more than half a millennium later. This meant that a lot of things were attributed to Thales and it can be very difficult to separate the truth from the hyperbole or outright fiction.

Plato and Aristotle tell two tales about Thales that are somewhat contradictory in their lesson and almost certainly apocryphal. The first comes from Plato in the Theaetetus, which is one of the Socratic dialogs concerning epistemology, that is, the nature of knowledge. The passage reads:

A case in point is that of Thales, who when he was star-gazing and looking upward, fell into a well, and was admonished, so it is said, by a clever and pretty maidservant from Thrace because he was eager to know what went on in the heavens, but did not notice what was in front of him, nay, at his very feet.

This is an amusing story and it actually makes it into Aesop’s fables, though the astronomer in Aesop’s version is unnamed. And it as an entirely familiar kind of story to us moderners. We still have the trope of the absent-minded professor and socially clueless geek. In fact, the modern sitcom The Big Bang Theory is essentially a show playing out this trope, following a group of people whose minds are filled with abstruse scientific theories, but who are hopelessly inept in managing their own lives, and this trope originates here with the ancient Greeks. But this kind of character is not a cultural universal, and speaks to the unique place that philosophers attained in ancient Greece. Certainly we see no stories poking fun of the Babylonian astronomer-priests for tumbling out of an observatory while drawing up a horoscope for the king.

The second story attributed to Thales comes to us through Aristotle’s Politics, and perhaps has the opposite implication about the personality of Thales.

Thales, so the story goes, because of his poverty was taunted with the uselessness of philosophy; but from his knowledge of astronomy he had observed while it was still winter that there was going to be a large crop of olives, so he raised a small sum of money and paid round deposits for the whole of the olive-presses in Miletus and Chios, which he hired at a low rent as nobody was competing with him; and when the season arrived, there was a sudden demand for a number of presses at the same time, and by letting them out on what terms he liked he realized a large sum of money, so proving that it is easy for philosophers to be rich if they choose, but this is not what they care about.

So this story is in essence, Aristotle’s answer to the question, “if you’re so smart, why aren’t you rich?” Thales said screw it, I will become rich.

Well, as I said earlier, both of these stories are almost certainly apocryphal. As much as I would like it to be otherwise, we now know that there is no way to use astronomy to predict olive harvests. But perhaps Thales used some other technique to try to anticipate demand for olive presses. He is today not only revered in the world of astronomy as an early astronomer, but in the world of finance as an early futures trader as well.

The accomplishment that Thales is best known for was probably more grounded in something that actually occurred, although here the story is still unfortunately murkier than we would like. This accomplishment was predicting the solar eclipse that occurred during the Battle of Halys, which is more commonly known as the Battle of the Eclipse. The account of this battle comes to us principally from Herodotus, who, unlike his contemporary Thucydides, was somewhat less critical about the stories that he heard and put into writing and would bend the truth for dramatic or moralistic purposes. Well, according to Herodotus, in the early 6th century BC, the Lydians were at war with the Medes. The Lydians were a Greek kingdom in the western part of Anatolia, or modern day Turkey. The Median Empire had originated out of Iran during the tumult of the Late Bronze Age Collapse and during the 7th century BC had taken advantage of the weakness of the Neo-Assyrian Empire to expand across the northern stretches of the fertile crescent and by the late 7th century had made it all the way to Anatolia. After losing some territory in the subsequent decades, a new Median king named Cyaxares regrouped and pushed the borders of Medes back to Lydia, probably around the Halys river which roughly divides Anatolia into its western and eastern halves.

Herodotus reports that in the 6th century BC, the Lydians and Medians had been at war for six years. Now it is probably the case that the real reason for this conflict was just the inevitable result of an expansionist empire seeking to swallow up its neighboring territories. But according to Herodotus, the casus belli was that a group of Scythians had been feuding with other Scythians and had arrived in Medes and sought protection from king Cyaxares in exchange for tribute. The Scythians were a nomadic group of low repute among the Greeks. You may remember the Scythians from episode 7 as being the barbaric tribe that drank wine undiluted. Cyaxares agreed to this arrangement and, as was apparently standard practice, sent a group of boys to live among the Scythians so that they could learn their language and any new military techniques. The Scythians would go hunting frequently and one day came back having caught nothing. Cyaxares was evidently in a bad mood and insulted the Scythians for failing in their hunt. So, in a story reminiscent of King Lycaon attempting to feed is son to Zeus, the Scythians took one of the Median boys, killed him, and prepared him the way they would a wild animal they had caught on the hunt and fed the boy to Cyaxares and his court. Naturally they had to get out of Medes after they were found out and moved west to Lydia and asked King Alyattes for protection. The Lydians agreed and refused to give up the Scythians to Cyaxares, thereby igniting the six-year conflict.

Why exactly the Lydians fought a six-year war on account of a group of men who had murdered a boy and fed him to the king, is not quite clear in Herodotus’s account. At any rate, the war was a stalemate and one day, as the battle was heating up, day turned into night. The combatants, seeing what had happened, understandably took it as a very bad omen indeed and put down their arms and arranged a peace treaty whereby King Alyattes gave his daughter in marriage to the son of Cyaxares.

Now, total solar eclipses are very rare. As I mentioned in Episode 4, a given patch of land only sees a solar eclipse every few hundred years on average. There are only a handful of total solar eclipses that occurred in that region during the relevant period, and the most likely candidate for this eclipse, was the eclipse of May 28, 585 BC. But there are a few problems with this. The first is that, at least according to Median king lists, Cyaxares had been dead for some ten years by this point. The other major problem is that this eclipse occurred fairly close to sunset at the location of the battle. But battles almost always began not long after sunrise even a long battle would typically finish by the heat of midday. But according to Herodotus, this eclipse occurred just as the battle was heating up, which seems hard to square with the eclipse happening so late in the day.

There were other solar eclipses in the region around that time, but none of them are total. Some of them were partial or annular, in some cases with 90% of the Sun being covered, but even if the Sun is 90% covered it’s actually hard to notice that anything is different unless you’re looking for it. It’s only when the Sun is closer to 97 or 98% covered that the darkening is really noticeable.

As with so many events in antiquity, it’s hard to prove anything conclusively. Probably the most plausible interpretation is that the battle really did happen on May 28, 585 BC but that Herodotus embellished some of the details about the eclipse happening in the heat of battle.

Well, so much for the battle itself, did Thales actually predict that this eclipse would happen, and if so, how? This is where things start to get very tricky. The main problem here is that solar eclipses are very, very difficult to predict. Lunar eclipses are relatively easy to predict because when a lunar eclipse happens it’s visible from anywhere on Earth where it’s night. This makes it easy to infer patterns of when the Moon will be full as it passes through a node. But a solar eclipse is more delicate. A total solar eclipse is only visible along a narrow strip of land on the Earth. It’s possible to come up with techniques to figure out that a solar eclipse will happen somewhere on Earth by looking at patterns of their occurrence in the same way that Babylonians developed the Saros cycle to predict lunar eclipses. But no one in the ancient world would have been able to compile tables of their occurrence because they could only observe them from a very limited region and they were so rare. And even if you can predict when an eclipse will occur, it’s far harder to figure out where those eclipses will occur.

The ancient Greeks eventually developed techniques to do this, but it was centuries later and only after many intermediate steps had been developed in astronomy. So if Thales had managed to figure out how to do this, he would have had to make centuries of progress in astronomy entirely on his own, and his techniques would have had to be completely lost to his successors.

Nevertheless, the story of Thales predicting the eclipse is relatively widespread in the ancient literature, so perhaps there is something to it. Of course, we need to take the predominance of something like this with a grain of salt, because perhaps all the later authors were simply parroting a tall tale told by Herodotus. Neither Plato nor Aristotle say anything about Thales and an eclipse. That said, if there is some truth to the story, it may have been the case that he had access to the Babylonian astronomical records. The later biographers state that he travelled to Egypt and learned astronomy there, and by this point in time the astronomy of Egypt had been heavily influenced by Babylonian astronomy. Moreover Thales was based in Miletus which is on the western coast of Anatolia and was quite close to the western extent of the Neo-Babylonian empire. So it is by no means out of the question that in his travels, Thales could have encountered Babylonian astronomical records.

From these, he could have learned of the Saros cycle that can be used to predict lunar eclipses. The Saros cycle can also be used to predict solar eclipses since lunar and solar eclipses come bunched together, namely whenever the moon is new or full as it passes through a node. But, of course, the trick here is how you know whether or not a solar eclipse will be visible at a given location. It is possible that Thales had simply noticed that 585 BC was during an eclipse season and that a solar eclipse of some kind was probably during the year. If that were the case, the fact that it turned out to be a total solar eclipse visible from a battlefield was simply a spectacular coincidence.

Another intriguing theory is that Thales didn’t predict the eclipse of 585 BC, but that this eclipse had produced so much consternation that he had assured the public that this was simply a natural event and that he could predict the next time this would occur. Thales could possibly have used a sort of generalization of the Saros cycle called the exeligmos cycle, which is about three times longer and more fully takes into account the quality of the eclipse, which can be correlated with where the eclipse will occur on Earth. Now, it’s important to note here that he could not have used the exeligmos cycle to predict the 585 eclipse because the previous eclipses in that cycle did not exist in the Babylonian record. But he could have predicted an eclipse in 582 or 581 BC based on these earlier records. In this theory, put forward by the Russian historian Dmitri Panchenko, Thales would have announced his prediction at the Pan-Ionian games, a predecessor of the Olympic games, and stated that an eclipse would be visible before the following Pan-Ionian games four years later. These were only partial or annular eclipses, but if the Greeks had been looking for them, they would have been easily visible.

Well, it’s frustrating to be constantly left in a state of uncertainty, but that’s usually how it goes with ancient history. We can make plausible arguments, but without new evidence it is very hard to say anything conclusive.

We can be a little more certain about certain details of his biography. Or at least, we have no evidence to contract those details. He was born in Miletus and was mixed race. Judging from the names of his parents his father was Phoenician and his mother Greek. It also seems to be the case that he traveled to Egypt and learned astronomy and mathematics there. As far as his personal life goes, Diogenes Laërtius tells, as you might expect, two stories which contradict each other. In one of the stories Thales is married, but in the other story he is not married and his mother pesters him asking why he hasn’t gotten married yet. He always responds by saying that he is too young to get married and will do so when he is older. Then one day he switches his story and says that he is too old to get married. The story about Thales being unmarried is in accordance with a story from Plutarch in which Solon asks him why he hasn’t gotten married and Thales responds that he didn’t want to worry about his children.

We unfortunately don’t know much about his cosmological ideas, only a few scraps of information persist through Aristotle. It seems that Thales’s cosmology was similar to that of the archaic Greeks that we discussed in the last episode on Homer and Hesiod. He conceived of the world as being a flat disc surrounded by the river Okeanus. But unlike the cosmology of Hesiod and Homer in which there is a cavernous region called Daedalus under the Earth, Thales believed that the Earth floated on a vast expanse of water. He argued that earthquakes were due to turbulence in this vast water.

The substance of water was foundational to Thales’s natural philosophy. To Thales, water was the source of all matter. The origin of the universe was in a vast ocean, out of which precipitated muddy terrain which then released its moisture to separate into dry land and an air, producing heat in the process. This cosmogony of course seems fairly fanciful to us, but it’s important to keep two things in mind. The first is that we are seeing this cosmogony through a glass darkly. There are only a few lines describing it by hostile authors many centuries later. So it’s very difficult to know Thales’s motivations for these ideas and the details of his theories. The second thing to keep in mind is that, naive though an idea like “all matter comes from water” may seem, it was the first in a long line of attempts to answer a question that dogged the Greek philosophers: what was the nature of matter? It is obvious enough that there are different kinds of matter, rocks and soil and plants and air and water, but also that some of these kinds of matter were related to each other. If you mixed wood and fire, you seemed to get a new kind of air. If you mixed water and earth, you got mud. And of course the metallurgists had found all kinds of ways to mix different kinds of rock with fire to produce various kinds of metals. So what were the relationships between these various kinds of matter? Were some more fundamental than others? Were they made up of discrete components or could you divide them up infinitely finely? These questions would be with the Greeks for centuries, but Thales was the first of many to engage with them.

On a more practical matter, Thales was credited with changing maritime navigation. You’ll recall in Episode 8 that Hesiod and Homer had mentioned that sailors used the Big Dipper to navigate. At that time, due to the precession of the equinoxes, the north celestial pole was actually somewhere between the Big and Little Dippers. But over the centuries it drifted closer towards Polaris. In fact it is still drifting closer towards Polaris today and will get closest to Polaris around 2100. Although the Little Dipper is less conspicuous than the Big Dipper, even during the time of Hesiod and Homer it would have been closer to the north celestial pole and made a better navigation aid, but both of them are quite clear that sailors of their day used the Big Dipper. But a few centuries later Greek navigators had learned to use the dimmer Little Dipper to find north and they attributed this development to Thales of Miletus.

You may also recall from the previous episode that Hesiod had noted the winter and summer solstices. But Thales was later credited with determining when the equinoxes were. This might seem to be somewhat trivial, but it is a more interesting discovery than it might seem because the equinoxes are not equally spaced between the summer and winter solstices. According to an author named Theon of Smyrna who quotes another author named Eudemus, Thales had discovered “the fact that the period of the sun with respect to the solstices is not always the same.” In modern terms, summer is longer than spring, which is longer than fall, which is longer than winter. Summer is about 93 1/2 days and winter is 89 days long. We now know that this inequality is due to the eccentricity of the Earth’s orbit. But while we don’t have any record of Thales proposing an explanation for his observation, explaining this anomaly between the lengths of the solstices and equinoxes came to occupy Greek astronomy for centuries.

There is one final discovery attributed to Thales and this is a measurement of the angular diameter of the Sun. The principle of the measurement is simple. You note when the Sun first starts to peak above the horizon at sunset, and then you measure the amount of time it takes before the Sun is completely above the horizon. Since the Sun moves 360 degrees over the course of 24 hours, this means it moves 15 degrees per hour and if you observe the Sun carefully during sunrise or sunset, you will find that it takes about two minutes between the time you first see the Sun pop above the horizon and when it has fully risen, which corresponds to an angular diameter of half a degree. Now, if you have very precise timepieces as you do today, you’ll find that this won’t be a great method to measure the Sun’s angular diameter to high precision because the Sun generally doesn’t rise exactly perpendicular to the horizon and atmospheric effects can make it difficult to determine exactly when the sunrise begins and ends. But at the tropics or the lower temperate latitudes it’s certainly good enough to make a measurement of about half a degree which is very close to the true value. According to Diogenes Laërtius, Thales measured this diameter to be 1/720th the circumference of a circle, which is half a degree.

But, when it comes to ancient astronomy, nothing can be as simple as you would like it to be. This technique had been known to the Babylonians and the Egyptians as well, but they reported that it took 1/30th of an hour for the Sun to rise. Now, this is about two minutes if we take an hour to mean its modern duration. But you’ll recall from Episode 5 that the hour the Babylonians used was actually two modern hours. So this would imply an angular diameter of one degree, twice as large as the true value. What is even more disconcerting is that none of the later Greeks use the value that Thales apparently measured. It doesn’t really show up again until the time of Archimedes some three centuries later, and when Aristarchus used this value around the same time to estimate the distance to the Moon, he used a wildly inaccurate value of two degrees. So if Thales indeed measured the angular diameter of the Sun, it seems clear that the particular result he obtained did not survive in Greek intellectual thought. In some ways this is not entirely implausible. Compared to the Babylonians, the Greeks were relatively uninterested in experimental measurements. For them it was sufficient to have devised a means to make the measurement. The particular value that resulted was of no special importance.

Well, regardless of the veracity of Thales’s apparent measurement, there is a nice story about the supposed discovery by Apuleius in a collection of his speeches called Florida, in which he writes

Thales is said to have communicated this discovery soon after it was made to Mandrolytus of Priene, who was greatly delighted with this new and unexpected information and asked Thales to say how much by way of fee he required to be paid to him for so important a piece of knowledge. “I shall be sufficiently paid”, replied tho sage, “if, when you set to work to tell people what you have learnt from me, you will not take credit for it yourself but will name me, rather than another as the discoverer.”

So, supposing this story is true, we could fairly call Thales the inventor of the academic citation.

Like many of the other Greek philosophers, Thales’s interests were not confined only to astronomy. He was apparently a gifted mathematician and has not one but two mathematical theorems named after him, both of which you would have learned in geometry even if his name wasn’t attached to them. The first is that if one of the sides of a triangle inscribed in a circle is a diameter of the circle, then the triangle is a right triangle. The second theorem states that if you take two parallel lines, and then draw two additional lines that intersect each other through the parallel lines to form two triangles, those triangles will be similar. Like his astronomical discoveries, later authors noted that he had learned his geometry during his travels in Egypt.

Thales also apparently had opinions on the nature of the soul, although as with his notion that water is the origin of all matter, it is hard to understand what exactly his ideas were on this. Apparently he believed that lodestones, natural magnets, had souls and that indeed, all things were full of gods. But again, all these notions come to us filtered through the lens of other ancient authors, in this case Aristotle, who had his own agenda. Unfortunately, unless some previously unknown document turns up in an archaeological dig, we will not get to see Thales face to face and will have to content ourselves with seeing him through a glass, darkly. The Thales we know of today is probably more legend than man, but even if a few of the discoveries attributed to him had some truth to them, if, for example, he had predicted an eclipse season or devised a method to measure the angular diameter of the Sun, his reputation as one of the great astronomers would be well deserved and he could certainly be considered to be the father of Greek astronomy. For a man about whom so few reliable pieces of concrete information exist, he still looms large in the culture even if it is only his reputation that survives.

Well, that is all I have to say about Thales of Miletus. In the next episode we will turn to some of the other early Greek astronomers in the so-called Ionian school, in particular Anaximander and Anaximenes. I hope you’ll join me then. Until the next full moon, good night, and clear skies.


  • https://www.purplemotes.net/2014/01/19/seven-sages-ostia/
  • Hall (2014), A History of the Archaic Greek World
  • Harris (1989) Ancient Literacy
  • https://en.wikipedia.org/wiki/Dipylon_inscription
  • https://en.wikipedia.org/wiki/Nestor%27s_Cup_(Pithekoussai)
  • http://articles.adsabs.harvard.edu/pdf/1994JHA….25..275P