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History of Science Ancient Egypt

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LibraryThing: Science in Ancient Mesopotamia Week 3: Ancient Egyptian and Aegean science

The Presocratics: Thales of Miletos, fl. 590 B.C.

| Presocratics Index | Intro | Thales | Anaximandros | Anaximenes | Herakleitos | Parmenides | Zenon | Melissos |
| Atomists: Leukippos and Demokritos | Anaxagoras | Empedokles | Significance of the Presocratics |

Miletos Theater (Wikipedia)According to Aristotle, Thales ("Thaw-lees") was the originator of the line of thinking about nature (physis) that led to physics. Thales lived in the Ionian colony of Miletos, the first town arranged in blocks, located on the west shore of Asia Minor near the Meander river (the convoluted course of this river is the origin of the term "meander" for an S-shaped or goose-necked bend).

Right: Theater of Miletos

Many encyclopedias and popular sources credit Thales with predicting a solar eclipse in 585 B.C. Yet there is no historical evidence that Thales did any such thing. If he knew how to predict eclipses (and solar eclipses are much harder to predict than lunar eclipses), it's odd that he taught none of his successors how to do it. Rather, the Greek historian Herodotos reported, over a century after Thales, that Thales had predicted a "darkening of the sun" that occurred during the war between the Lydians and the Medes, who broke off the battle and ended the war. Herodotos reported further that Thales foretold the event to the Ionians "to the very year." This evidence is much more vague than is often supposed! (What if you were the only source for future generations about Abraham Lincoln, and you only mentioned him in passing?) But because modern astronomers can determine that a solar eclipse, visible in Asia Minor, occurred in 585 B.C., they assume that Herodotos must have been referring to that eclipse, when it is much more likely that Thales predicted a drought year with a dust storm. (Nor is there independent historical evidence that the battle between the Lydians and Medes occurred during that solar eclipse.) The most that can be said is that by the time of Herodotos, Thales had a vague reputation for vaguely foretelling a vague kind of darkening event.

Another story often told about Thales is the earliest known joke about an absent-minded professor: One night Thales was out walking in the field, looking up at the stars. He became so engrossed in the sky that he did not watch where he was going and fell into a well. When his servant girl, Thratta, rescued him, she laughed, saying, "In his zeal for things in the sky he does not see what is at his feet."

However, Thales of Miletos is more than the stuff of legend. That he was a historical person is attested by a row of lion statues approaching the Temple of Didyma in Miletos. The names of donors are inscribed on the lions, and one of them is "Thales" (it is now in the British Museum). The boustrophedon writing and the style of the letters (e.g., a short-legged lambda) date the lions to circa 600-575 B.C. So there was a Thales of Miletos, possessed of some wealth and held in high regard by his contemporaries, to whom later writers attributed a host of stories and accomplishments.

More likely than the other stories is Herodotos' report that Thales gave the Lydian king, Kroisos, advice about how to cross the Hallas river without having to wait to build a bridge. Kroisos camped with his soldiers on a neck of land surrounded by a meander of the river. During the night, Thales diverted half of the river across the neck of the meander, behind the soldiers' camp. This reduced the original stream to an easily fordible depth. At the very least, by the time of Herodotos, Thales had a reputation for giving wise advice.

Why was Thales important enough to make up stories about?

Thales’ contributions to science included cryptic aphorisms after the manner of a mantic prophet, which may be variously “decoded” into propositions of pertinence to physics. Here are the two most important sayings:

1. “All things are full of gods.”
Aristotle interpreted this saying as implying a principle of movement (or animism) within nature. In his words:

Aristotle. On the Soul, i. 2; 405 a 19. and i. 5 ; 411 a 7.
"And Thales, according to what is related of him, seems to have regarded the soul as something endowed with the power of motion, if indeed he said that the loadstone has a soul because it moves iron.... Some say that soul is diffused throughout the whole universe; and it may have been this which led Thales to think that all things are full of gods."

What is this animating principle of movement (= change) within nature that Aristotle discerned in this saying? The gods are immortal. Therefore, if all things are full of gods, then there must be something within each thing that is immortal; that is the first principle (archai) of things. In other words, Thales was regarded as having implicitly posed the problem of change, by asserting that there exists some first principle or immortal divinity that persists through change in the same way that immortal gods continue through time. Often regarded as a kind of "conservation of matter principle," this idea also represents contemporary efforts to rationalize and reform anthropomorphic religious ideas of the "divine," i.e., that on which all else depends.

2. “All things are water.”
If there is a first principle of all things, which is an immortal divinity and persists through changes, then what is it? Thales' answer to that question was hugely important. Here is how a later writer put it:

Hipp. i. ; Dox. 555.
"It is said that Thales of Miletos, one of the seven wise men, was the first to undertake the study of physical philosophy. He said that the beginning (the first principle) and the end of all things is water. All things acquire firmness as this solidifies, and again as it is melted their existence is threatened; to this are due earthquakes and whirlwinds and movements of the stars. And all things are movable and in a fluid state, the character of the compound being determined by the nature of the principle from which it springs. This principle is god, and it has neither beginning nor end." (Hanover Historical Texts Project)

Aristotle displayed some bewilderment about the reason that might have caused Thales to conclude that all things are composed of water, and so he speculated on some possible grounds for this belief. Here is Aristotle's explanation:

Aristotle. Metaphysics. i. 3 ; 983 b 6ff.
"Most of the early students of philosophy thought that first principles in the form of matter, and only these, are the sources of all things; for that of which all things consist, the antecedent from which they have sprung, and into which they are finally resolved (in so far as being underlies them and is changed with their changes), this they say is the element and first principle of things... As to the quantity and form of this first principle, there is a difference of opinion; but Thales, the founder of this sort of philosophy, says that it is water (accordingly he declares that the earth rests on water), getting the idea, I suppose, because he saw that the nourishment of all beings is moist, and that warmth itself is generated from moisture and persists in it (for that from which all things spring is the first principle of them); and getting the idea also from the fact that the germs of all beings are of a moist nature, while water is the first principle of the nature of what is moist. And there are some who think that the ancients, and they who lived long before the present generation, and the first students of the gods, had a similar idea in regard to nature; for in their poems Okeanos and Tethys were the parents of generation, and that by which the gods swore was water, -- the poets themselves called it Styx; for that which is most ancient is most highly esteemed, and that which is most highly esteemed is an object to swear by. Whether there is any such ancient and early opinion concerning nature would be an obscure question; but Thales is said to have expressed this opinion in regard to the first cause." (Hanover Historical Texts Project)

It is more important here to examine how Thales’ successors (up to and including Aristotle) interpreted him than how he understood himself, but even Aristotle suggests that there was a continuity between the Greek mythological tradition (Okeanos and Tethys) and Thales' selection of water as the divine principle of all things. Today one seeking mythological precedents for Thales' claims on behalf of water would go farther back than Aristotle, beyond Greek mythology, to the "deep" or "Apsu" which was the source of the world in Mesopotamian mythology.

But from Aristotle’s point of view, what mattered was that with Thales and his immediate successors, “nature” had been conceived in a universal, abstract way, and identified as deriving from one substance (water), that persists through every change. We may characterize Thales’ position as one of “physical monism,” because it made the world dependent on a single, divinized, impersonal principle -- water.

First principle
Thales of Miletos


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HSCI 3013. History of Science to 17th centuryCreative Commons license
Kerry Magruder, Instructor, 2004
Brent Purkaple, TA

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Many thanks to the pedagogical model developed in Mythology and Folklore and other online courses by Laura Gibbs, which have been an inspiration for this course.

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