Publication of the Tetrabiblos
Tetrabiblos publication · Ptolemy's codification
What happened
Claudius Ptolemy of Alexandria published the Tetrabiblos (Four Books) around 150 CE — the first canonical work systematizing Hellenistic-era astrological knowledge. Four books: 1. principles and celestial mechanics, 2. mundane astrology (states, weather, wars), 3. natal astrology (personal chart), 4. forecasting techniques. Before the Tetrabiblos astrology was scattered: Babylonian, Egyptian, Greek, Chaldean schools running in parallel, terminology unresolved. Ptolemy gathered these in one language, filled gaps with systematic logic, and advanced the thesis "astrology is a natural science" — not prophecy but inclination-reading.
Why it matters
The "canon" of modern astrology. Used as a practical foundation for 1,800 years. House system, aspects, modalities, elements — all there. The later Hellenistic revival treats this text as the guide too.
Themes
- canon established
- systematization
- astrology as natural science
- lasting foundation