Thales of Miletus is conventionally regarded as the first Western philosopher — the Milesian thinker of the early sixth century BCE whose claim that water is the source and substance of all things began the Greek philosophical tradition.
thales
The Milesian thinker of the early sixth century BCE conventionally regarded as the first Western philosopher — the originator of the Greek tradition of natural philosophy through his claim that water is the source and substance of all things.
Birth around 624 BCE, death around 546 BCE. Both dates approximate; established largely from the prediction of the solar eclipse of 585 BCE that Herodotus attributes to him.
Introduction
Thales of Miletus is conventionally regarded as the first Western philosopher. The early-sixth-century-BCE Milesian thinker is the figure with whom Aristotle's Metaphysics I.3 (the canonical ancient history of early Greek philosophy) begins the tradition; Aristotle treats Thales as the originator of the inquiry into the arche (the first principle or originative source) of all things and credits him with the claim that water is the source of all things. The claim, simple as it appears, established the framework within which the entire Milesian school (Thales, Anaximander, Anaximenes) and the broader Pre-Socratic tradition would operate: the project of identifying a single principle from which the diverse phenomena of the world can be understood.
No writings by Thales survive. The biographical and doctrinal information comes from later sources — principally Herodotus (mid-fifth century BCE), Aristotle (fourth century BCE), Theophrastus (late fourth century BCE, whose lost Opinions of the Physicists shaped the entire subsequent doxographical tradition), and Diogenes Laertius (third century CE). The reliability of the reports varies; some are credible (the eclipse prediction, the engineering contributions) while others are clearly later legend (the story of Thales falling into a well while observing the stars, told by Plato in the Theaetetus).
Life and biography
Thales was born around 624 BCE in Miletus, a Greek colony on the Ionian coast of Anatolia (now western Turkey) that was, in the early sixth century, the wealthiest and most culturally engaged Greek city in the eastern Mediterranean. The family was probably Phoenician in origin, though long since Hellenized.
Herodotus reports that Thales predicted the solar eclipse of May 28, 585 BCE — a prediction whose accuracy impressed his contemporaries and that gives the most-cited single date in early Greek philosophy. (Modern scholarship has questioned whether Thales could in fact have predicted the eclipse using techniques available at the time; the eclipse occurred, and Thales received credit for the prediction, regardless of the precise method.)
The other biographical reports concern engineering and political achievements. Thales was credited with redirecting the Halys River for King Croesus of Lydia, with measuring the height of the Egyptian pyramids using the shadow method, with introducing geometrical proof to the Greeks, and with proposing a federation of Ionian city-states to resist Persian expansion. Some of these reports may be later constructions; the consistent picture is of a polymathic engineer-philosopher whose contributions extended across natural philosophy, mathematics, astronomy, and political affairs.
The doctrine
The canonical doctrine — water is the source of all things — is reported by Aristotle in Metaphysics I.3 (983b20–27). Aristotle's report includes his own attempt to reconstruct the reasoning that may have led Thales to the claim: the seed of every living thing is moist; food is moist; the source of life is connected with moisture in evident ways; the inference to water as the underlying principle of all things follows from extending the observed connection across the natural world.
The claim has been interpreted in several distinct ways. The literal reading: water is the actual material substance from which all other things are made through physical transformation. The metaphor reading: water is the paradigmatic example of a substance that exhibits the changes of state and the transformations that characterize the natural world. The theological reading (reported in some ancient sources): water is the original generative principle out of which the divine ordering of the cosmos proceeds.
Which reading Thales himself intended cannot be settled from the surviving evidence. What matters historically is that the question — what is the source of all things? — became, with Thales, the founding question of the Western philosophical tradition.
Other reported doctrines
Thales is credited with several other claims that the doxographical tradition preserves. The earth floats on water (a cosmological claim that explained the stability of the earth and the occurrence of earthquakes). The magnet has a soul (a claim that extended the concept of psychē beyond animal life to include the powers of attraction observed in mineral substances). All things are full of gods (a claim reported by Aristotle in De Anima I.5 that has been interpreted variously as pantheism, as panpsychism, and as a more general claim about the divine character of natural processes).
The geometrical contributions reported in later sources include the theorem that the angles at the base of an isosceles triangle are equal, the theorem that a circle is bisected by any diameter, the theorem on the equality of vertical angles, and the theorem still known as Thales's theorem (that an angle inscribed in a semicircle is a right angle). Whether Thales actually proved these theorems in the form later geometers would recognize as proof is contested; the consistent picture is of a thinker engaged with the questions about geometrical structure that would become central to the Greek mathematical tradition.
Reception
The ancient reception of Thales established him as the founding figure of the Greek philosophical tradition. Aristotle's Metaphysics I.3 placed him at the beginning of the history of philosophy; Diogenes Laertius's Lives of the Eminent Philosophers Book I opens with Thales; the tradition of the Seven Sages of Greece (the seven legendary wise men of the early sixth century BCE) consistently included Thales among the seven.
The modern reception has been shaped by the nineteenth-century recovery of Pre-Socratic philosophy through Friedrich Schleiermacher, Eduard Zeller, and the nineteenth-century German classicism. Hermann Diels's Die Fragmente der Vorsokratiker (1903) gave the canonical edition of the Pre-Socratic fragments and testimonia. The twentieth-century work of G. S. Kirk, J. E. Raven, and Malcolm Schofield (The Presocratic Philosophers, 1957; revised 1983) and the more recent Loeb Classical Library edition by André Laks and Glenn Most (2016) provide the dominant contemporary scholarly resources.
The contemporary scholarship on Thales is necessarily speculative because of the absence of writings; the major recent monographs (Patricia O'Grady, Thales of Miletus, 2002) work cautiously through the doxographical sources to reconstruct what can be plausibly said about the earliest Western philosopher.
Further reading
- Pre-Socratic — the tradition Thales founded
- Heraclitus — the major Ionian successor in natural philosophy
- Parmenides — the Eleatic philosopher whose denial of change responded to the Milesian project
- Aristotle — the major source for Thales's doctrines in Metaphysics I.3
The Milesian thinker of the early sixth century BCE conventionally regarded as the first Western philosopher and the originator of the Greek tradition of natural philosophy.