Knowra Thales of Miletus Thales of Miletus Thales of Miletus was an ancient Greek thinker traditionally counted among the first philosophers and mathematicians. Later accounts credit him with explaining nature through natural principles rather than divine action.
Miletus : An ancient Greek city on the coast of Ionia, in present-day Turkey. Thales lived in this prosperous Ionian city, a center of trade and intellectual exchange.
Ionia : An ancient Greek region on the western coast of Anatolia, including cities such as Miletus. Thales belonged to the Ionian world where early Greek inquiry into nature took shape.
Anaximander : A sixth-century BCE Milesian thinker who proposed the boundless, or apeiron, as the source of things. Tradition makes him a successor to Thales who replaced water with a different first principle.
Thales' theorem : A geometry result stating that an angle inscribed in a semicircle is a right angle. A later tradition attaches this theorem to Thales, though its historical attribution is uncertain.
History of ancient philosophy : The study of philosophical ideas and traditions in the ancient Mediterranean and neighboring societies. Reconstructing Thales depends on evaluating sources written centuries after his lifetime.
Presocratic philosophy : Greek philosophical inquiry before Socrates, spanning diverse accounts of nature, knowledge, and reality. Thales is conventionally placed at the beginning of this broad tradition.
Milesian school : A traditional name for early natural philosophers associated with Miletus, especially Thales, Anaximander, and Anaximenes. This grouping connects Thales with two successors who proposed different basic principles.
Anaximenes : A sixth-century BCE Milesian philosopher who identified air as the fundamental source of the cosmos. His account of air continues the search for a single natural principle associated with Thales.
Similar triangles : Triangles with equal corresponding angles and proportional corresponding side lengths. Reports credit Thales with using proportional triangles to estimate inaccessible heights.
Presocratic doxography : The later compilation and transmission of reports about early Greek philosophers and their doctrines. Most surviving claims about Thales come through this chain of retrospective reporting.
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