2. There can be no doubt that the founder of the Milesian school, and therefore the first of the cosmologists, was Thales;[[55]] but all we can really be said to know of him comes from Herodotos, and the romance of the Seven Wise Men was already in existence when he wrote. He tells us, in the first place, that Thales was of Phoenician descent, a statement which other writers explained by saying he belonged to the Thelidai, a noble house descended from Kadmos and Agenor.[[56]] This is clearly connected with the view of Herodotos that there were “Kadmeians” from Boiotia among the original Ionian colonists, and it is certain that there really were people called Kadmeians in several Ionic cities.[[57]] Whether they were of Semitic origin is, of course, another matter. Herodotos probably mentions the supposed descent of Thales simply because he was believed to have introduced certain improvements in navigation from Phoenicia.[[58]] At any rate, the name Examyes, which his father bore, lends no support to the view that he was a Semite. It is a Karian name, and the Karians had been almost completely assimilated by the Ionians. On the monuments, we find Greek and Karian names alternating in the same families, and there is therefore no reason to suppose that Thales was anything else than an ordinary Milesian citizen, though perhaps with Karian blood in his veins.[[59]]
The eclipse foretold by Thales.
3. By far the most remarkable statement that Herodotos makes about Thales is that he foretold the eclipse of the sun which put an end to the war between the Lydians and the Medes.[[60]] Now, we may be sure that he was quite ignorant of the true cause of eclipses. Anaximander and his successors certainly were so,[[61]] and it is incredible that the right explanation should once have been given and then forgotten so soon. Even supposing, however, Thales had known the cause of eclipses, no one can believe that such scraps of elementary geometry as he picked up in Egypt would enable him to calculate one from the elements of the moon’s path. Yet the evidence for the prediction is too strong to be rejected off-hand. The testimony of Herodotos to an event which must have happened about a hundred years before his own birth may, perhaps, be deemed insufficient; but that of Xenophanes is a very different matter, and it is this we have really to deal with.[[62]] According to Theophrastos, Xenophanes was a disciple of Anaximander, and he may quite well have seen and spoken with Thales. In any case, he must have known scores of people who were able to remember what happened, and he had no conceivable interest in misrepresenting it. The prediction of the eclipse is really better attested than any other fact about Thales whatsoever, and the evidence for it is about as strong as for anything that happened in the early part of the sixth century B.C.
Now it is quite possible to predict eclipses without knowing their true cause, and there is no doubt that the Babylonians actually did so. On the basis of their astronomical observations, they had made out a cycle of 223 lunar months, within which eclipses of the sun and moon recurred at equal intervals of time.[[63]] This, it is true, would not enable them to predict eclipses of the sun for a given spot on the earth’s surface; for these phenomena are not visible at all places where the sun is above the horizon at the time. We do not occupy a position at the centre of the earth, and what astronomers call the geocentric parallax has to be taken into account. It would only, therefore, be possible to tell by means of the cycle that an eclipse of the sun would be visible somewhere, and that it might be worth while to look out for it. Now, if we may judge from a report by a Chaldaean astronomer which has been preserved, this was just the position of the Babylonians. They watched for eclipses at the proper dates; and, if they did not occur, they announced the fact as a good omen.[[64]] To explain what we are told about Thales no more than this is required. He simply said there would be an eclipse; and, as good luck would have it, it was visible in Asia Minor, and on a striking occasion.
Date of Thales.
4. The prediction of the eclipse does not, then, throw much light upon the scientific attainments of Thales; but, if we can fix its date, it will give us a point from which to start in trying to determine the time at which he lived. Modern astronomers have calculated that there was an eclipse of the sun, probably visible in Asia Minor, on May 28 (O.S.), 585 B.C.,[[65]] while Pliny gives the date of the eclipse foretold by Thales as Ol. XLVIII. 4 (585/4 B.C.).[[66]] This, it is true, does not exactly tally; for May 585 belongs to the year 586/5 B.C. It is sufficiently near, however, to justify us in identifying the eclipse as that of Thales, and this is confirmed by Apollodoros, who fixed his floruit in the same year.[[67]] The further statement that, according to Demetrios Phalereus, Thales “received the name of wise” in the archonship of Damasias at Athens, agrees very well with this, and is doubtless based on the story of the Delphic tripod; for the archonship of Damasias is the era of the restoration of the Pythian Games.[[68]]
Thales in Egypt.
5. The introduction of Egyptian geometry into Hellas is universally ascribed to Thales, and it is extremely probable that he did visit Egypt; for he had a theory of the inundations of the Nile. In a well-known passage,[[69]] Herodotos gives three explanations of the fact that this alone of all rivers rises in summer and falls in winter; but, as his custom is in such cases, he does not name their authors. The first of them, however, that which attributes the floods to the Etesian winds, is ascribed to Thales in the Placita,[[70]] and also by many later writers. Now, those statements are derived from a treatise on the Rise of the Nile attributed to Aristotle and known to the Greek commentators, but now extant only in a Latin epitome of the thirteenth century.[[71]] In this work the first of the three theories mentioned by Herodotos is ascribed to Thales, the second to Euthymenes of Massalia, and the third to Anaxagoras. Where did Aristotle, or whoever wrote the book, get these names? We think naturally once more of Hekataios, whom Herodotos so often reproduces without mentioning his name; and this conjecture is much strengthened when we find that Hekataios actually mentioned Euthymenes.[[72]] We may conclude, then, that Thales really was in Egypt; and, perhaps, that Hekataios, in describing the Nile, took account, as was only natural, of his distinguished fellow-citizen’s views.
Thales and geometry.
6. As to the nature and extent of the mathematical knowledge brought back by Thales from Egypt, it seems desirable to point out that many writers have seriously misunderstood the character of the tradition.[[73]] In his commentary on the First Book of Euclid, Proclus enumerates, on the authority of Eudemos, certain propositions which he says were known to Thales.[[74]] One of the theorems with which he credits him is that two triangles are equal when they have one side and the two adjacent angles equal. This he must have known, said Eudemos, as otherwise he could not have measured the distances of ships at sea from a watch-tower in the way he was said to have done.[[75]] Here we see how all these statements arose. Certain remarkable feats in the way of measurement were traditionally ascribed to Thales, and it was assumed that he must have known all the propositions which these imply. But this is quite an illusory method of inference. Both the measurement of the distance of ships at sea, and that of the height of the pyramids, which is also ascribed to him,[[76]] are easy applications of what Aahmes calls the seqt. These rules of mensuration may well have been brought from Egypt by Thales, but we have no ground for supposing that he knew any more about their rationale than did the author of the Rhind papyrus. Perhaps, indeed, he gave them a wider application than the Egyptians had done. Still, mathematics, properly so called, did not come into existence till some time after Thales.