Dec 17, 2010 - the first, Thales is a genius who actually accomplished all that ... Don't take your father's bad points. ... Keep evil things hidden at home.
4 Thales of Miletus Thales of Miletus, famed as the originator of Greek philosophy and science, lived in the first part of the sixth century, as is shown by the stories of his prediction of the solar eclipse of 585 BCE. Thales is a figure of legendary wisdom in many fields, from engineering to politics, from applied economics to science. He was known as the founder of Greek mathematics and astronomy as well as of philosophy. He was also reputed as a sage, a kind of combination of Solomon and Benjamin Franklin who authored short sayings of practical advice. (“The man’s a Thales!” exclaims a character in one of Aristophanes’ comedies1 written a century and a half after Thales lived.) He is unique among the early philosophers in being associated with so wide a range of activities. In fact, many scholars doubt that Thales actually was responsible for so many deeds and discoveries, and for good reason, as we will see. But how far can skepticism reasonably go? There are three general approaches to interpreting Thales: the credulous, the skeptical, and the historically tempered. On the first, Thales is a genius who actually accomplished all that antiquity reports. On the second, he is truly a man of legend: a historical person to whom various exploits and accomplishments (some of them genuine, but achieved by others) have been falsely attributed. On the third, he is a gifted but historically plausible person whose actual accomplishments were transformed by tradition into works of genius. Which of these approaches (or what combination of them) we decide is correct has crucial importance for our understanding of the beginning of Greek philosophy. I shall return to this issue at the end of the chapter and also in Chapter 8. But first I will present Thales’ achievements as they are reported and some of the interpretations they have received. In an oft-told story,2 King Croesus of Lydia asked Thales for help in transporting his army across the river Halys, and Thales made it passable by diverting its course upstream from the army’s position, so that some or all the water flowed behind the camp, rejoining the original riverbed downstream. Here we have a practical Thales involved in engineering projects, whose reputation was so great that foreign monarchs consulted him. However, the military expedition in question, Croesus’s attack on the Persian army, took place almost forty years after the eclipse, a date that seems to some impossibly (or improbably) late for Thales’ active participation. (We do not know when he was born or died.) He is said to have advised the Ionian cities of Asia Minor to form a political union with a centrally located common governing council,3 advice which if taken might have 1. Aristophanes, Birds line 1009 (not in DK). 2. The earliest source is Herodotus, Histories 1.75 = DK 11A6. Other sources are cited as well at DK 11A6. 3. Herodotus, Histories 1.170 = DK 11A4. 21
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made the Ionian cities better able to resist Persian expansion. However, this story is rendered historically implausible by the same considerations, namely the time when the Persians were threatening the Ionian Greeks seems too late to have occurred in the period of Thales’ activity. Further, he has a reputation as a sage. Later ages assembled a list of the Seven Sages, like the Seven Wonders of the World, and various deeds and pieces of proverbial wisdom are assigned to them. They are all historical personages who lived in the sixth century. Thales is the only Presocratic named among the Seven Sages,4 a clear indication of his fame as a wise man in later generations. One author credits a number of sayings to each of the Seven, including the following, which he ascribes to Thales. 4.1
Remember friends both present and absent. Don’t beautify your face, but be beautiful in what you do. Don’t acquire wealth immorally. Don’t hesitate to flatter your parents. Don’t take your father’s bad points. However many feasts you hold in honor of your parents, your children will hold for you. It is difficult to know oneself. The sweetest thing is to get what you desire. Laziness is incurable. Incontinence is harmful. Lack of education is a burden. Teach and learn what is better. Don’t be late, even if you are wealthy. Keep evil things hidden at home. It is better to be envied than pitied. Be moderate. Don’t believe everyone. (Demetrius of Phaleron, Sayings of the Seven Sages, quoted in Stobaeus, 3.1.172 = DK 10, 3)
However, it would be a mistake to accept these alleged quotations at face value. The content of the sayings reveals a good deal about traditional attitudes and beliefs, but most people agree that these maxims were well known and were assigned to the Seven Sages by later compilers for want of more information about their authors. As the earliest subject of both an “absent-minded professor” story and a defense of philosophy against charges of uselessness, Thales is emblematic of the different responses philosophy provoked in its cultural setting. 4.2
They say that once when Thales was gazing upwards while doing astronomy, he fell into a well, and that a witty and charming Thracian serving-girl made fun of him for being eager to know the things in the heavens but failing to notice what was just behind him and right by his feet. (Plato, Theaetetus 174a = DK 11A9)
4.3
The story goes that when they were reproaching him for his poverty, supposing that philosophy is useless, he learned from his astronomy that the olive crop would be large. Then, while it was still winter, he obtained a little
4. The earliest reference to the Seven Sages includes Thales among their number. It is found in Plato, Protagoras 343a = DK 10,2.
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money and made deposits on all the olive presses both in Miletus and in Chios, and since no one bid against him, he rented them cheaply. When the time came, suddenly many requested the presses all at once, and he rented them out on whatever terms he wished, and so he made a great deal of money. In this way he proved that philosophers can easily be wealthy if they wish, but this is not what they are interested in. (Aristotle, Politics 1.11 1259a9–18 = DK 11A10)
Astronomy These no doubt fictitious stories portray Thales as an astronomer, which chimes with his prediction of the eclipse. But here we run across the central problem in understanding Thales. Did he really found Western science and philosophy? Or did he simply parrot the theories and discoveries of others? Or is the story a total fabrication? First, what did his prediction actually say? We do not have his words; the earliest report is given by the fifth-century historian Herodotus. In recounting a war between the Medes and the Lydians he says: 4.4
As they were having equal success in the war, it happened that in the sixth year, when a battle was being fought, the day suddenly became night. Thales of Miletus had foretold to the Ionians that this loss of daylight would occur, setting as a limit the very year in which the event occurred. (Herodotus, Histories 1.74 = DK 11A5)
Two things should be noticed in Herodotus’s account. Thales predicted the year of the eclipse, not the date or time of day, and he is not said to have predicted that the eclipse would be visible at any specific place. If Herodotus is an accurate guide, Thales’ prediction, if it existed, did not resemble modern ones, which specify not just the year but the day and the path of the eclipse and the time of partial and total eclipse at different places along its path. Modern predictions require much precise knowledge that was not available until much later (for example, the elliptical orbits of earth and moon were determined in the 17th century), and although some needed facts, such as the sphericity of the earth, were known in later antiquity, there is no reason to suppose that Thales knew them.5 It is clear that Thales could not have predicted the eclipse in the same way that astronomers do today. But this does not necessarily mean that he did not predict the eclipse in some other way. An attractive alternative is that he based his prediction on Babylonian astronomy. Here the idea is that if solar eclipses are recorded over a sufficiently long time—longer than a single person’s lifetime—patterns of their 5. The evidence for this assertion is the astronomy of Thales’ immediate successors, which does not recognize a spherical earth and which was in other ways grossly unsuited to making accurate predictions of celestial phenomena.
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occurrences emerge which can be used to make rough predictions even without modern astronomical knowledge. The Babylonians, keenly interested in eclipses and other astronomical phenomena for astrological and religious purposes, kept meticulous records from the mid-eighth century and so had a data base sufficient for such limited predictions. Thales is said to have traveled to Egypt, and given Miletus’s international connections he may have visited Babylon too. Alternatively, people versed in Babylonian astronomy may have visited Miletus. In these circumstances, Thales may have learned to make predictions himself or may merely have reported a Babylonian prediction. But this approach is doomed as well. Babylonian astronomy was never capable of predicting when an eclipse would occur at a specific location. Eventually it could say when an eclipse might occur (which is a matter of predicting when the moon is in the same place in the sky as the sun6) but the determination of whether it would occur in a particular place was not achieved prior to Ptolemy’s Almagest (c.150 CE). On the other hand, there is some more concrete evidence that Thales was interested in eclipses. 4.5
Thales said that the sun suffers eclipse when the moon comes to be in front of it, the day in which the moon produces the eclipse being marked by its concealment. (P.Oxy. 53.3710, col. 2, 37–40 [not in DK])
This information is taken from a quotation of Aristarchus (third century BCE) in a commentary on Homer’s Odyssey.7 According to this text, Thales knew the cause of solar eclipses: that the moon is between the sun and the earth and so blocks the sun’s light. But this knowledge does not amount to a method of predicting eclipses. Since the concealment referred to is most likely to be not the concealment of the sun (namely, the eclipse) but that of the moon, Aristarchus is asserting that Thales knew that eclipses occur at new moon (the phase when the moon is invisible), which is the period when its celestial longitude is very near to that of the sun. This is not improbable. A person interested in solar and lunar phenomena, including the apparent motion of the moon relative to the sun, and who observed one or more solar eclipses could be expected to note that the eclipse took place at new moon. From here it would be but a small step to the conclusion that eclipses always take place at this phase of the moon’s cycle—in other words, that a necessary condition for a solar eclipse is that it occur at new moon—and it would be a larger but not unimaginably larger step to the conclusion that the position of the moon in the sky during an eclipse coincides with 6. That is, when the celestial longitude and latitude of the moon and sun are identical, which occurs when the moon and sun are in conjunction (have the same longitude) at a lunar node (when the moon is at the ecliptic). See Aaboe (1972). 7. This text is discussed in Bowen and Goldstein (1994).
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that of the sun. From here it would be natural to infer the correct account of solar eclipses as due to the moon’s interposition between the earth and the sun. I see no reason against thinking that Thales could have gone so far (although I am cautious about asserting that he actually did), but I remain skeptical about the possibility of his being able to predict when an eclipse will actually occur.8 In any case it is likely that Thales had an interest in astronomical phenomena. In addition to the eclipse, he is plausibly said to have investigated the solstices and equinoxes, the seasons of the year, and the number of days in the year and month. These phenomena have to do with the sun and moon, and their investigation requires careful and sustained observations but nothing that could not have been done at any time by a person interested in understanding the phenomena in question.9
Mathematics In his History of Geometry, Aristotle’s follower Eudemus reports that Thales introduced geometry to Greece from Egypt, made discoveries of his own, and transmitted to posterity the principles of many theorems, “attacking some more generally and others more perceptually.”10 Among other achievements11 he is credited with the theorem that triangles with one side and the two adjacent angles equal are congruent, for “he must have used this theorem to show the distance of ships at sea in the way he did.”12 This statement gives a clue to how later historians of geometry approached their subject, and also leads us once more to question Thales’ originality. Greek geometry, as canonized in Euclid’s Elements (c.300 BCE), proceeds by proofs based on definitions and other unproved principles. It deals more with general theorems than with specific problems and is not primarily devoted to calculations. In these respects it differs from earlier mathematics, including Egyptian geometry. Ancient historians of mathematics from Eudemus on assumed that Greek geometry had this distinctive character from the start and that it developed cumulatively, with successive mathematicians contributing proofs of new theorems or organizing existing knowledge into a comprehensive system of proofs. Accordingly, they said that Thales, the founder of Greek mathematics, passed on the principles of many theorems to posterity, and they sought to attribute particular theorems to him. Recent historians of Greek mathematics reject this approach. 8. For a more optimistic account of Thales as eclipse-predictor, see Panchenko (1994). 9. For further discussion, see White (2008). 10. Eudemus, cited in Proclus, Commentary on the First Book of Euclid’s Elements 65.7–11 = DK 11A11. 11. He is also said to have “demonstrated” that a circle is bisected by its diameter, that the base angles of an isosceles triangle are equal, and that if two straight lines intersect, the vertical angles are equal (ibid., 157.10, 250.20, 299.1 = DK 11A20). 12. Ibid., 352.14–18 = DK 11A20.
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The notion of proving results is unlikely to have sprung full grown from the head of the first Greek geometer like Athena from the head of Zeus, but more probably developed over an extended period of time, perhaps influenced by the use of proofs in philosophy, which are not found before Parmenides.13 The mention of Thales’ use of the angle-side-angle congruence theorem to show the distance of ships at sea indicates the following method or something equivalent to it. From two points on the shore (A, B) determine the angles between shore and ship (a, b). Construct equal angles on the shoreward side of those points and continue the lines until they intersect (C). The distance from C to the line between A and B will be equal to the distance from that line to the ship.
A
a a
b b
B
C This application of geometry does presuppose knowing certain properties of triangles, but contrary to Eudemus’s inferences it implies nothing about Thales’ inventing a proof of the angle-side-angle theorem or of his having a concept of proof. It does not even make it certain that he stated the theorem generally or that he had the technical vocabulary (“angle,” “congruent”) to do so. Eudemus’s vague assertion that Thales attacked some theorems “more generally and others more perceptually” may give insight into the nature of Thales’ “proofs.” His proof that a circle is bisected by its diameter,14 perhaps involved folding or cutting a drawn circle and showing that the two pieces match. Such an argument might be called perceptual. Nowadays this kind of procedure would not count as a legitimate proof, and even by Euclid’s day it had fallen out of favor. But it does contain the germ of the idea of mathematical proof (showing one fact to follow from others and seeing that the result applies generally to all circles and their diameters, not just to the one used in the actual proof) and constitutes a decisive step away from the practical and empirical mathematics of the Egyptians. On the other hand, skeptics argue, if we are dubious about the claims that Thales discovered these theorems, we should be equally dubious about the proof 13. Parmenides is the subject of Ch. 11. 14. Eudemus, cited in Proclus, Commentary on the First Book of Euclid’s Elements 157.10–11 = DK 11A20.
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he is said to have found. It would be simple enough for someone at a later date who wanted to attribute some specific mathematical discoveries to Thales to have credited him with a few simple theorems that anyone with a little geometry would know and to have credited him with a simple and primitive sounding proof for one of them. Thales’ claim to be the founder of Greek mathematics is as uncertain as his credentials as the first Greek astronomer. So far Thales is an ambiguous figure. He may have made original scientific discoveries (inventing the notion of proof would make him one of the most important figures in the entire history of human thought); he may have simply imported the scientific knowledge of other peoples; and he may have done nothing at all in these areas. His speculations about water, however, belong to quite a different area of endeavor.
Water Aristotle’s survey of some of the opinions of his philosophical forebears contains the most important testimonium about Thales, which I divide into several sections. 4.6
Causes are spoken of in four ways, of which . . . one is matter. . . . Let us take as associates in our task our predecessors who considered the things that are and philosophized about the truth, for it is clear that they too speak of certain principles and causes, and so it will be useful to our present inquiry to survey them: either we will find some other kind of cause or we will be more confident about the ones now being discussed. (Aristotle, Metaphysics 1.3 983a26–b6 [not in DK])
Aristotle’s purposes are clear. He does not aim to discuss the complete theories of former philosophers sympathetically and in context; he wants only to see if they contain anything relevant to his own philosophical project of identifying different types of causes. His starting points are his own notion of “cause” and his view that there are precisely four kinds of causes, and despite his assertion in the final sentence, he proves reluctant to acknowledge additional kinds, let alone to admit any radically different approach to the subject of causes. He continues with a strongly Aristotelian account of what a “material cause” is. 4.7
Of those who first pursued philosophy, the majority believed that the only principles of all things are principles in the form of matter. For that of which all existing things are composed and that from which they originally come to be and that into which they finally perish—the substance persisting but changing in its attributes—this they state is the element and principle of the things that are. . . . For there must be one or more natures from which the rest come to be, while it is preserved. (Aristotle, Metaphysics 1.3 983b6–18 = DK 11A12)
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This notion of underlying matter was Aristotle’s invention. Even though earlier thinkers regarded one or more kinds of things as somehow primary, Aristotle is anachronistic in assuming that their notions of primacy coincided with his (in particular with his developed notion of “substance”), or even that their theories addressed the problems that engaged him. He goes on to mention Thales. 4.8
However, they do not all agree about how many or what kinds of such principles there are, but Thales, the founder of this kind of philosophy, stated it to be water. (This is why he declared that the earth rests on water.) He may have got this idea from seeing that the nourishment of all things is moist, and that even the hot itself comes to be from this and lives on this (the principle of all things is that from which they come to be)—getting this idea from this consideration and also because the seeds of all things have a moist nature; and water is the principle of the nature of moist things. (Aristotle, Metaphysics 1.3 983b18–27 = DK 11A12) (continuation of 4.7)
This passage tells us three things. (a) Thales says the earth floats on water, (b) Aristotle interprets Thales as declaring that water is the “material cause” as defined in 4.7, and (c) Aristotle has to guess Thales’ reasons for giving primacy to water. If Aristotle infers (b) from (a), we must question Thales’ originality again. For in discussing another passage which attributes (a) to Thales, Simplicius remarks: 4.9
Aristotle speaks quite strongly against this view, which was prevalent perhaps because the Egyptians recounted it in mythological form and Thales may have imported the doctrine from there. (Simplicius, Commentary on Aristotle’s On the Heavens 522.16–18 = DK 11A14)
Again, we may have borrowing from Egypt; this time the borrowing is not of science but of myth. Aristotle himself is aware of Greeks who advanced mythical ways of thought, but makes it clear that Thales was not one of them. 4.10
Some believe that the people of remote antiquity, long before the present generation, who were the first to speculate about the gods, had this idea about nature too. For they made Ocean and Tethys parents of coming to be and made water, which the poets called Styx, the oath by which the gods swore. For the most ancient is the most honored, and the most honored thing is what is used to swear by. (Aristotle, Metaphysics 1.3 983b27–33 = DK 11A12) (continuation of 4.8)
For Aristotle, Thales is a philosopher, not a speculator about the gods, and I think that this is one interpretation that we are bound to accept. Thales was said to have contributed to many areas of thought, but mythology is not one of them.
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Thales’ claim that the earth rests on water may have been intended to explain natural phenomena. One source tells us that Thales held that the motion of this subterranean water was the cause of earthquakes.15 If this was his view, Thales made a decisive break with the traditional belief that earthquakes are caused by Poseidon.16 Moreover, in hypothesizing an unobserved natural state of affairs (no one had seen the earth resting on water) to explain an observed phenomenon, Thales made an intellectual move which has remained a principal part of scientific thinking to this day. It is unlikely that Thales wrote down his views on water as a cosmological principle. If Aristotle had any such book he would not have been so vague and so quickly driven to guesswork. Still, he regards Thales as the founder of his own philosophical and scientific tradition, not just an importer of foreign ideas or a teller of myths like Homer and Hesiod (who are behind the reference to Ocean and Tethys in 4.10). Even if Thales’ ideas stem from mythology, at the very least he demythologizes them, and this is a crucial move for philosophy and science. How, then, did he present the demythologized ideas? There are two main lines of interpretation. First, the traditional view, which follows Aristotle, is that for Thales in some way all things are water; they are made or composed of water. Thus, Thales’ main question is “What are all things made of?” and as far as we know he was the first to ask this question, and his answer is of the same type as those given by later Presocratics and by physicists up to the present day. The idea that everything is water is open to a number of objections which not only seem obvious to us, but which Thales’ immediate successors avoid in their theories—objections such as, “If everything is composed of water, how can there be different kinds of things in the world, some of them, such as fire, seemingly opposed to water?” and “Even if (as Aristotle indicates) water is necessary for the origin and maintenance of other things, why should we think that water is their only constituent?” It is unclear what if any response Thales would make to these criticisms. But in this period it is not surprising if theories are open to obvious objections, and the mere fact that there are decisive reasons to reject a theory is no reason at all to think it was not actually held. On the second interpretation, towards which I incline and which is actually better supported than the first by Aristotle’s discussion in 4.8, Thales’ principal question is, “What is the origin of all things?”17 In identifying water as the origin he harks back to Greek and Near Eastern mythological accounts of the origin of the earth, with which his assertion that the earth floats on water fits nicely. On this view, Thales’ interests are somewhat different from those of his successors, although many of them were concerned with the origin 15. Seneca, Natural Questions 3.14 = DK 11A15. 16. Since Poseidon was also the god of the sea, it is possible that by attributing earthquakes to the movement of water, Thales was offering a naturalistic account of phenomena that eliminated the need to refer to this Olympian god at all. 17. The key word, arkhē can mean “origin” and “beginning” as well as “principle.”
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of the world as well as its physical constitution. Thales’ question stems from the past, but his answer, grounded in the nature of the world around us rather than in the family history of the gods, rejected tradition and provided a starting point for his successors.
Souls and Gods Aristotle reports that Thales believed magnets possess soul because they move iron, and infers that he judged the soul to be a thing that causes motion.18 Thales also held that amber (which has magnetic properties when rubbed or heated) possesses soul.19 It is hard to know what to make of these statements. The idea that the soul is the principle of life was widespread in Greek thought. The presence of soul makes a thing alive; when a living thing dies, it no longer has a soul. Thus, Aristotle held that plants and animals possess souls. He held further that motion is characteristic of life, especially in his broad sense of “motion,” which includes growth and changes in quality—“motions” which even plants possess. Thus, the presence of soul, and therefore of life, implies motion. Thales attributes soul to things not normally thought to be alive. Is he proposing a version of hylozoism, the view that matter has life, so that life is found in all things whatever? Also, since magnets and amber cause other things to move, is Thales’ point that the notion of soul should be extended to include things that themselves are motionless but make other things move? Or instead of moving in these exciting new directions does he just want to reinforce (in a nonmythological context) a pre-philosophical animistic conception that many parts of what we regard as inanimate nature are actually alive? The following passage may help resolve these questions. 4.11
Some declare that it [the soul] is mixed in the whole [the universe], and this may be why Thales thought all things are full of gods. (Aristotle, On the Soul 1.5 411a7–8 = DK 11A22)
Here Aristotle says that Thales believes all things are full of gods and suggests, without asserting confidently, that he believes soul pervades the whole world and that these two ideas are related. If the link between souls and gods is valid (an assumption which is possible, though not certain), Thales’ most important surviving doctrines can be connected as follows, though the interpretation is speculative and the elements of Thales’ thought it pulls together may have been separate.
18. Aristotle, On the Soul 1.2 405a19 = DK 11A22. 19. Diogenes Laertius, Lives of the Philosophers 1.24 = DK 11A1.
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Water is primary since it is prominent in the physical makeup of the world (occurring not only on the earth but also above it in the form of rain and below it as the water on which the earth floats), and it is needed for the generation and maintenance of living things and of some apparently nonliving things. Thales conceives of water not as a chemically pure substance but as moisture quite generally—in the sea, in rain, in sperm. Water’s unceasing mobility, seen especially in the continuous movement of the sea, rivers, and rain, reveals it to be living and so possessing a soul. Since everything is made of water or ultimately arises from water, the life-force of water pervades the whole world, showing up in some things more than others (just as some things are wetter than others). Moreover, as a living thing with no beginning in time (everything else owes its beginning to it) and apparently no end in time either, water is divine (since for the Greeks the primary characteristics of the divine are immortality and power independent of human will). Hence all things, being composed of or arising from water, are full of the divine. (This is not to say that they have any relation to the Olympian gods; in fact, the claim that all things are full of gods is to be understood in the context of Thales’ demythologized world view.) Thales is a threshold figure, standing at the beginning of the Western scientific and philosophical tradition, but strongly influenced by the past. Of the little we know about him, much fits both the picture of Thales as the brilliant innovator and also that of Thales as the importer of others’ ideas. While skepticism is appropriate, it must be kept within bounds, and few would be so skeptical as to say that Thales did nothing (although some not unreasonably say that we cannot be at all sure about what he did); there must be a reason why all those stories were attributed to Thales and not to someone else. But even if we reject his credentials as the first Greek astronomer and geometer, his views on water as the material principle and his apparent rejection of the Olympian gods and traditional Greek mythology are harder to dismiss, and they are what led Aristotle to name him the first philosopher. Although Thales remains a Janus-faced figure, the same cannot be said of Anaximander, the second Milesian philosopher, whose originality and imagination are beyond doubt.
