Thales theorem and first proofs
Teorema de Tales y primeras demostraciones
- Date
- c. 600 BCE · confidence low
- Place
- Miletus, Ionia (Turkey)
- Credited to
- Thales of Miletus
- People
- 👤 Tales de Mileto650 BCE–548 BCE
- Field
- Knowledge & symbols
⚠️ Disputed: the sources disagree.
What was discovered
Statements on the proportionality of segments cut by parallel lines and on the angle inscribed in a semicircle. Tradition credits him as the first to justify geometric properties through reasoning rather than recipes.
No writing by Thales survives; the attributions come from Proclus and Eudemus, centuries later.
What it led to
- Greek deductive geometry
- the Pythagorean school
- Euclid's Elements
Built on
- Egyptian and Babylonian practical geometry
Made possible
- Euclid Elements and the axiomatic methodc. 300 BCE
- measuring heights by shadows
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