Tetrabiblos (Τετράβιβλος - The Four Books)
Historical Significance & The Alexandrian Tradition
Composed in second-century Roman Alexandria by the celebrated astronomer and mathematician Claudius Ptolemy, the Tetrabiblos (“Four Books”) served as the standard academic textbook of astrology across the Byzantine Empire, Medieval Islamic caliphates (where it was known as Kitab al-Arba’a), and Latin Renaissance Europe.
Unlike earlier omen-based texts, Ptolemy approached astrology as a natural philosophy grounded in Aristotelian physics:
“A very few consider the power of the heavenly bodies, and their effects upon terrestrial matters, to be worthy of deep philosophical contemplation… that the Sun, Moon, and stars govern season, heat, moisture, and bodily temperaments according to physical necessity.”
Structure of the Four Treatises
Book I: Technical Foundations & Planetary Physics
- The Active Powers of the Planets: Classifies planets by primary qualities:
- Sun: Heating and moderately drying.
- Moon: Moistening and moderately heating.
- Saturn: Excessively cold and dry.
- Mars: Excessively hot and dry.
- Jupiter: Moderately hot and moist (fertile/benefic).
- Venus: Moderately moist and warm (benefic).
- Mercury: Dual and adaptable to surrounding planetary aspects.
Book II: Mundane & Meteorological Horoscopy
- Eclipses and planetary ingresses over countries and cities.
- Regional rulerships by triplicity and geographical quadrants.
- Weather forecasting through planetary stations, comets, and heliacal risings.
Book III: Natal Horoscopy & Physical Destiny
- Calculation of the Conception and Birth Horoscopes.
- The Giver of Life (Hyleg) and the Destroyer of Life (Anareta).
- Parents, siblings, physical constitution, and longevity.
Book IV: Soul, Fortune, Profession & Marriage
- Mental qualities and intellectual inclinations governed by Mercury and the Moon.
- Professional destiny ruled by the Sun and Oriental planets.
- Marriage, children, foreign travel, and the Quality of Death.
Core Predictive Principles in the Tetrabiblos
1. Essential Dignities (The Ptolemaic Table)
Ptolemy standardized the five levels of planetary dignity across the 360° tropical zodiac:
- Domicile (Rulership): Where a planet rules its own house.
- Exaltation: A sign of supreme elevation and honor.
- Triplicity: Elemental agreement (Fire, Earth, Air, Water).
- Terms (Bounds): Sub-zodiacal segment allotments regulating specific degrees.
- Decans (Faces): 10-degree divisions based on Chaldean order.
2. Major Classical Aspects (Ptolemaic Rays)
Only five aspects were recognized by Ptolemy based on sacred geometric division of the circle:
- Conjunction (0°): Unity of rays.
- Sextile (60°): Harmonious cooperation (elemental compatibilities).
- Square (90°): Dynamic tension and conflict.
- Trine (120°): Perfect harmony and effortless grace.
- Opposition (180°): Polarization, confrontation, and direct sight.