Chapter I., the Milesian School
Total Page:16
File Type:pdf, Size:1020Kb
CHAPTER I., THE MILESIAN SCHOOL 1. MiletusandLydia 2. Origin 3. TheEclipseForetoldby Thales 4. DateofThales 5. ThalesinEgypt 6. ThalesandGeometry 7. ThalesasaPolitician 8. UncertainCharacteroftheTradition 9. TheCosmologyofThales 10. Water 11. Theology 12. TheLifeofAnaximander 13. TheophrastusonAnaximander'sTheoryofthePrimarySubstance 14. ThePrimarySubstanceisNotOneoftheElements 15. Aristotle'sAccountoftheTheory 16. ThePrimarySubstanceisInfinite 17. TheInnumerableWorlds 18. "EternalMotion"andthe Dinê 19. OriginoftheHeavenlyBodies 20. EarthandSea 21. TheHeavenlyBodies 22. Animals 23. TheLifeofAnaximenes 24. HisBook 25. TheoryofthePrimarySubstances 26. RarefactionandCondensation 27. Air 28. TheWorldBreathes 29. ThePartsoftheWorld 30. InnumerableWorlds 31. InfluenceofAnaximenes 30 1.MiletusandLydia IT was at Miletos that the earliest school of scientific cosmology hadits home, andit is not, perhaps, without significance that Miletos is just the place where the continuity of AegeanandIonian civilisation is most clearly marked.1 The Milesians had come into conflict more than once with the Lydians, whose rulers were bent onextending their dominiontothe coast; but, towards the endof the seventhcentury B.C., the tyrant Thrasyboulos succeededin making terms withKing Alyattes, and an alliance was concludedwhichsecuredMiletos against molestationfor the future. Evenhalf a century later, when Croesus, resuming his father's forward policy, made war upon and conquered Ephesos, Miletos was able tomaintainthe old treaty-relation, andnever, strictly speaking, became subject tothe Lydians at all. The Lydian connexion, moreover, favouredthe growth of science at Miletos. What was calledat a later date Hellenism seems tohave been traditional inthe dynasty of the Mermnadai, and Herodotos says that all the "sophists" of the time flockedtothe court of Sardeis.2 The traditionwhich represents Croesus as the "patron" of Greek wisdom was fully developed in the fifth century; and, however unhistorical its details may be, it must clearly have some foundation in fact. Particularly noteworthy is "the commontale among the Greeks," that Thales accompaniedCroesus onhis luckless campaignagainst Pteria, apparently inthe capacity of military engineer. Herodotos disbelieves the story that he divertedthe course of the Halys, but only because he knew there were bridges there already. It is clear that the Ionians were great engineers, and that they were employed as such by the eastern kings.3 It shouldbe added that the Lydian alliance would facilitate intercourse with BabylonandEgypt. Lydia was anadvancedpost of Babylonianculture, andCroesus was onfriendly terms withthe kings of Egypt andBabylon. Amasis of Egypt hadthe same Hellenic sympathies as Croesus, andthe Milesians possessedatempleoftheirownatNaukratis. I. THALES 2.Origin The founder of the Milesianschool, andtherefore the first manof science, was Thales;4 but all we canreally be saidtoknow of him comes from Herodotos, andthe Tale of the SevenWise Menwas already inexistence when he wrote. He says that Thales was of Phoeniciandescent, a statement which other writers explainedby saying he belongedtoa noble house descendedfrom Kadmos andAgenor.5 Herodotos probably mentions the supposeddescent of Thales simply because he was believedtohave introduced certain improvements in navigation from Phoenicia.6 At any rate, his father's name, Examyes, lends nosupport tothe view that he was a Semite. It is Karian, andthe Karians hadbeen 31 almost completely assimilatedby the Ionians. On the monuments we find Greek andKariannames alternatinginthesamefamilies,whilethenameThalesisotherwiseknownasCretan.Thereistherefore noreasontodoubt that Thales was of pure Milesian descent, thoughhe probably hadKarianbloodin hisveins.7 3.TheEclipseForetoldbyThales Themost remarkablestatementHerodotosmakesaboutThalesis thatheforetoldtheeclipseof the sunwhichput anend tothe war betweenthe Lydians andthe Medes.8 Now, he was quite ignorant of the cause of eclipses. Anaximander andhis successors certainly were so,9 andit is incredible that the explanation should have been given and forgotten so soon. Even supposing Thales had known the cause of eclipses, such scraps of elementary geometry as he picked up in Egypt would never have enabledhim tocalculate one. Yet the evidence for the predictionis toostrong tobe rejectedoff-hand. The testimony of Herodotos is said to have been confirmed by Xenophanes,10 and according to Theophrastos Xenophanes was a disciple of Anaximander. Inany case, he must have knownscores of people whowere able to remember what happened. The predictionof the eclipse is therefore better attestedthananyotherfactaboutThaleswhatsoever. Now it is possible topredict eclipses of the moon approximately without knowing their true cause, andthere is nodoubt that the Babylonians actually didso. It is generally stated, further, that they hadmade outa cycle of 223 lunar months, within whicheclipses of the sunandmoonrecurredat equal intervals of time.11 This, however, wouldnot have enabledthem topredict eclipses of the sun for a givenspot onthe earth's surface; for these phenomena are not visible at all places where the sunis above the horizon at the time. We do not occupy a position at the centre of the earth, and the geocentric parallax has tobe takenintoaccount. It wouldonly, therefore, be possible to tell by means of the cycle that aneclipse of the sunwouldbe visible somewhere, andthat it might be worthwhile to look out for it, though anobserver at a givenplace might be disappointedfive times out of six. Now, if we may judge from reports by Chaldaeanastronomers whichhave beenpreserved, this was just the positionof the Babylonians inthe eighthcentury B.C. They watchedfor eclipses at the proper dates; and, if they did not occur, they announced the fact as a good omen.12 To explain what we are told about Thales nomore is required. He saidthere wouldbe aneclipse by a certaindate; andluckily it was visibleinAsiaMinor,andonastrikingoccasion.13 4.TheEclipseForetoldbyThales The predictionof the eclipse does not, then, throw any light onthe scientific attainments of Thales;but,ifwecanfixitsdate,itwillgiveusanindicationofthetimeatwhichhelived.Astronomers 32 have calculatedthat there was aneclipse of the sun, probably visible inAsia Minor, onMay 28 (O.S.), 585 B.C., while Pliny gives the date of the eclipse foretoldby Thales as Ol. XLVIII.4 (585/4 B.C.).14 This does not exactly tally; for May 585 belongs to the year 586/5 B.C. It is near enough, however, to justify us inidentifying the eclipse as that of Thales,15 andthis is confirmedby Apollodoros, who fixed his floruit inthe same year.16 The further statement inDiogenes that, according toDemetrios Phalereus, Thales"receivedthenameofwise"inthearchonshipofDamasiasatAthens, reallyreferstotheTale of the SevenWise Men,as is shownby the words whichfollow, andis doubtless basedonthe story of the Delphictripod;forthearchonshipofDamasiasistheeraoftherestorationof thePythianGames.17 5.ThalesinEgypt The introductionof Egyptiangeometry intoHellas is ascribedtoThales,18 andit is probable that he did visit Egypt; for he had a theory of the inundations of the Nile. Herodotos19 gives three explanations of the fact that this alone of all rivers rises in summer and falls in winter; but, as his custom is, he does not name their authors. The first, however, whichattributes the rise of the Nile to the Etesianwinds, is ascribed to Thales in the Placita,20 and by many later writers. Now, this comes from a treatise onthe Rise of the Nile attributedtoAristotle andknowntothe Greek commentators, but extant only ina Latinepitome of the thirteenthcentury.21 Inthis the first of the theories mentioned by Herodotos is ascribed to Thales, the second to Euthymenes of Massalia, and the third to Anaxagoras. Where didAristotle, or whoever wrote the book, get these names? We think naturally of Hekataios; andthis conjecture is strengthenedwhen we findthat Hekataios mentionedEuthymenes.22 We may conclude that Thales really was inEgypt; and, perhaps, that Hekataios, indescribing the Nile, tookaccount,aswasnatural,ofhisfellow-citizen's views. 6.ThalesandGeometry As to the nature and extent of the mathematical knowledge brought back by Thales from Egypt, it must be pointed out that most writers have seriously misunderstood the character of the tradition.23 Inhis commentary onthe First Book of Euclid, Proclus enumerates, onthe authority of Eudemos, certain propositions which he says were known to Thales,24 one of which is that two triangles are equal when they have one side and the two adjacent angles equal. This he must have known, as otherwise he couldnot have measuredthe distances of ships at sea inthe way he was saidto have done.25 Here we see how all these statements arose. Certainfeats inthe way of measurement were traditionally ascribedtoThales, andEudemos assumedthat he must have knownall the propositions these imply. But this is quite illusory. Boththe measurement of the distance of ships at sea, andthat of the height of the pyramids, whichis alsoascribedtohim,26 are easy applications of the rule givenby Aahmes for finding the seqt.27 What the traditionreally points tois that Thales appliedthis empirical 33 rule topractical problems whichthe Egyptians had never faced, andthat he was thus the originator of generalmethods.Thatisasufficienttitletofame. 7.ThalesasaPolitician Thales appears once more inHerodotos some time before the fall of the Lydianmonarchy. He is saidtohave urgedthe IonianGreeks tounite in a federal state withits