Thales of Miletus (c. 624/623 – c. 548/545 BC) was a Greek mathematician, astronomer and pre-Socratic philosopher from Miletus in Ionia, Asia Minor. He was one of the Seven Sages of Greece. Many, most notably Aristotle, regarded him as the first philosopher in the Greek tradition, and he is otherwise historically recognized as the first individual in Western civilization known to have entertained and engaged in scientific philosophy.
Thales is recognized for breaking from the use of mythology to explain the world and the universe, and instead explaining natural objects and phenomena by naturalistic theories and hypotheses, in a precursor to modern science. Almost all the other pre-Socratic philosophers followed him in explaining nature as deriving from a unity of everything based on the existence of a single ultimate substance, instead of using mythological explanations. Aristotle regarded him as the founder of the Ionian School and reported Thales’ hypothesis that the originating principle of nature and the nature of matter was a single material substance: water.
In mathematics, Thales used geometry to calculate the heights of pyramids and the distance of ships from the shore. He is the first known individual to use deductive reasoning applied to geometry, by deriving four corollaries to Thales’ theorem. He is the first known individual to whom a mathematical discovery has been attributed.
The dates of Thales’ life are not exactly known, but are roughly established by a few datable events mentioned in the sources. According to Herodotus, Thales predicted the solar eclipse of May 28, 585 BC. Diogenes Laërtius quotes the chronicle of Apollodorus of Athens as saying that Thales died at the age of 78 during the 58th Olympiad (548–545 BC) and attributes his death to heat stroke while watching the games.
Thales was probably born in the city of Miletus around the mid-620s BC. The ancient writer Apollodorus of Athens writing during the 2nd century BC, thought Thales was born about the year 625 BC. Herodotus, writing in the fifth century BC, described Thales as “a Phoenician by remote descent”. Tim Whitmarsh noted that Thales regarded water as the primal matter, and because thal is the Phoenician word for moisture, his name may have derived from this circumstance.”
According to the later historian Diogenes Laërtius, in his third century AD Lives of the Philosophers, references Herodotus, Duris, and Democritus, who all agree “that Thales was the son of Examyas and Cleobulina, and belonged to the Thelidae who are Phoenicians.” Their names are indigenous Carian and Greek, respectively. Diogenes then states that “Most writers, however, represent him as a native of Miletus and of a distinguished family.” However, his supposed mother Cleobulina has also been described as his companion. Diogenes then delivers more conflicting reports: one that Thales married and either fathered a son (Cybisthus or Cybisthon) or adopted his nephew of the same name; the second that he never married, telling his mother as a young man that it was too early to marry, and as an older man that it was too late. Plutarch had earlier told this version: Solon visited Thales and asked him why he remained single; Thales answered that he did not like the idea of having to worry about children. Nevertheless, several years later, anxious for family, he adopted his nephew Cybisthus.
It has been claimed that he was roughly the professional equivalent of a contemporary option trader.
It is assumed that Thales at one point in his life visited Egypt, where he learned about geometry. Diogenes Laërtius wrote that Thales identifies the Milesians as Athenian colonists.
Thales (who died around 30 years before the time of Pythagoras and 300 years before Euclid, Eudoxus of Cnidus, and Eudemus of Rhodes) is often hailed as “the first Greek mathematician”. While some historians, such as Colin R. Fletcher, point out that there could have been a predecessor to Thales who would have been named in Eudemus’ lost book History of Geometry, it is admitted that without the work “the question becomes mere speculation.”Fletcher holds that as there is no viable predecessor to the title of first Greek mathematician, the only question is whether Thales qualifies as a practitioner in that field; he holds that “Thales had at his command the techniques of observation, experimentation, superposition and deduction…he has proved himself mathematician.”
Aristotle wrote in Metaphysics, “Thales, the founder of this school of philosophy, says the permanent entity is water (which is why he also propounded that the earth floats on water). Presumably he derived this assumption from seeing that the nutriment of everything is moist, and that heat itself is generated from moisture and depends upon it for its existence (and that from which a thing is generated is always its first principle). He derived his assumption from this; and also from the fact that the seeds of everything have a moist nature, whereas water is the first principle of the nature of moist things.”
Reliability of sources
Because of Thales’ elevated status in Greek culture an intense interest and admiration followed his reputation. Due to this following, the oral stories about his life were open to amplification and historical fabrication, even before they were written down generations later. Most modern dissension comes from trying to interpret what we know, in particular, distinguishing legend from fact.
Historian D.R. Dicks and other historians divide the ancient sources about Thales into those before 320 BC and those after that year (some such as Proclus writing in the 5th century C.E. and Simplicius of Cilicia in the 6th century C.E. writing nearly a millennium after his era). The first category includes Herodotus, Plato, Aristotle, Aristophanes, and Theophrastus among others. The second category includes Plautus, Aetius, Eusebius, Plutarch, Josephus, Iamblichus, Diogenes Laërtius, Theon of Smyrna, Apuleius, Clement of Alexandria, Pliny the Elder, and John Tzetzes among others.
The earliest sources on Thales (living before 320 BC) are often the same for the other Milesian philosophers (Anaximander, and Anaximenes). These sources were either roughly contemporaneous (such as Herodotus) or lived within a few hundred years of his passing. Moreover, they were writing from an oral tradition that was widespread and well known in the Greece of their day.
The latter sources on Thales are several “ascriptions of commentators and compilers who lived anything from 700 to 1,000 years after his death” which include “anecdotes of varying degrees of plausibility” and in the opinion of some historians (such as D. R. Dicks) of “no historical worth whatsoever”. Dicks points out that there is no agreement “among the ‘authorities’ even on the most fundamental facts of his life—e.g. whether he was a Milesian or a Phoenician, whether he left any writings or not, whether he was married or single-much less on the actual ideas and achievements with which he is credited.”
Contrasting the work of the more ancient writers with those of the later, Dicks points out that in the works of the early writers Thales and the other men who would be hailed as “the Seven Sages of Greece” had a different reputation than that which would be assigned to them by later authors. Closer to their own era, Thales, Solon, Bias of Priene, Pittacus of Mytilene and others were hailed as “essentially practical men who played leading roles in the affairs of their respective states, and were far better known to the earlier Greeks as lawgivers and statesmen than as profound thinkers and philosophers.” For example, Plato praises him (coupled with Anacharsis) for being the originator of the potter’s wheel and the anchor.
Only in the writings of the second group of writers (working after 320 BC) do “we obtain the picture of Thales as the pioneer in Greek scientific thinking, particularly in regard to mathematics and astronomy which he is supposed to have learnt about in Babylonia and Egypt.” Rather than “the earlier tradition [where] he is a favourite example of the intelligent man who possesses some technical ‘know how’…the later doxographers [such as Dicaearchus in the latter half of the fourth century BC] foist on to him any number of discoveries and achievements, in order to build him up as a figure of superhuman wisdom.”
Dicks points out a further problem arises in the surviving information on Thales, for rather than using ancient sources closer to the era of Thales, the authors in later antiquity (“epitomators, excerptors, and compilers”) actually “preferred to use one or more intermediaries, so that what we actually read in them comes to us not even at second, but at third or fourth or fifth hand. …Obviously this use of intermediate sources, copied and recopied from century to century, with each writer adding additional pieces of information of greater or less plausibility from his own knowledge, provided a fertile field for errors in transmission, wrong ascriptions, and fictitious attributions”. Dicks points out that “certain doctrines that later commentators invented for Thales…were then accepted into the biographical tradition” being copied by subsequent writers who were then cited by those coming after them “and thus, because they may be repeated by different authors relying on different sources, may produce an illusory impression of genuineness.”
Doubts even exist when considering the philosophical positions held to originate in Thales “in reality these stem directly from Aristotle’s own interpretations which then became incorporated in the doxographical tradition as erroneous ascriptions to Thales”. (The same treatment was given by Aristotle to Anaxagoras.)
Most philosophic analyses of the philosophy of Thales come from Aristotle, a professional philosopher, tutor of Alexander the Great, who wrote 200 years after Thales’ death. Aristotle, judging from his surviving books, does not seem to have access to any works by Thales, although he probably had access to works of other authors about Thales, such as Herodotus, Hecataeus, Plato etc., as well as others whose work is now extinct. It was Aristotle’s express goal to present Thales’ work not because it was significant in itself, but as a prelude to his own work in natural philosophy. Geoffrey Kirk and John Raven, English compilers of the fragments of the Pre-Socratics, assert that Aristotle’s “judgments are often distorted by his view of earlier philosophy as a stumbling progress toward the truth that Aristotle himself revealed in his physical doctrines.” There was also an extensive oral tradition. Both the oral and the written were commonly read or known by all educated men in the region.
Aristotle’s philosophy had a distinct stamp: it professed the theory of matter and form, which modern scholastics have dubbed hylomorphism. Though once very widespread, it was not generally adopted by rationalist and modern science, as it mainly is useful in metaphysical analyses, but does not lend itself to the detail that is of interest to modern science. It is not clear that the theory of matter and form existed as early as Thales, and if it did, whether Thales espoused it.
While some historians, like B. Snell, maintain that Aristotle was relying on a pre-Platonic written record by Hippias rather than oral tradition, this is a controversial position. Representing the scholarly consensus Dicks states that “the tradition about him even as early as the fifth century B.C., was evidently based entirely on hearsay….It would seem that already by Aristotle’s time the early Ionians were largely names only to which popular tradition attached various ideas or achievements with greater or less plausibility”. He points out that works confirmed to have existed in the sixth century BC by Anaximander and Xenophanes had already disappeared by the fourth century BC, so the chances of Pre-Socratic material surviving to the age of Aristotle is almost nil (even less likely for Aristotle’s pupils Theophrastus and Eudemus and less likely still for those following after them).
The main secondary source concerning the details of Thales’ life and career is Diogenes Laërtius, “Lives of Eminent Philosophers”. This is primarily a biographical work, as the name indicates. Compared to Aristotle, Diogenes is not much of a philosopher. He is the one who, in the Prologue to that work, is responsible for the division of the early philosophers into “Ionian” and “Italian”, but he places the Academics in the Ionian school and otherwise evidences considerable disarray and contradiction, especially in the long section on forerunners of the “Ionian School”. Diogenes quotes two letters attributed to Thales, but Diogenes wrote some eight centuries after Thales’ death and that his sources often contained “unreliable or even fabricated information”, hence the concern for separating fact from legend in accounts of Thales.
It is due to this use of hearsay and a lack of citing original sources that leads some historians, like Dicks and Werner Jaeger, to look at the late origin of the traditional picture of Pre-Socratic philosophy and view the whole idea as a construct from a later age, “the whole picture that has come down to us of the history of early philosophy was fashioned during the two or three generations from Plato to the immediate pupils of Aristotle”.