Quadrant

Definition

A four-sector division of the chart created by the intersection of the Ascendant-Descendant horizon axis and the MC-IC meridian axis. Each quadrant contains three houses; reading the chart counter-clockwise from the Ascendant, the four quadrants are houses 1-3, 4-6, 7-9, and 10-12. In medieval astronomy 'quadrant' also names a graduated 90° arc instrument used for measuring altitudes and angular distances — one of the standard tools listed by Bonatti alongside the astrolabe and armillary sphere.

In Tradition

In modern psychological Western practice the four quadrants are read as developmental zones of the chart — Howard Sasportas's framing (self-development, self-expansion, self-expression, self-transcendence) gives a humanistic gloss to the four-fold division and is preserved through the Centre for Psychological Astrology lineage as the finest-grained sub-analysis of chart-shape methodology.

In Practice

When you read a chart by quadrants, you note where the chart's planetary weight clusters — a hemisphere or quadrant emphasis is one of the standard shape-readings. Quadrant emphasis in the lower half (houses 1-6) reads toward personal and private themes; upper half (7-12) toward relational and public themes; eastern half (10-3) toward self-directed initiative; western half (4-9) toward relational responsiveness. Quadrant-house systems (Placidus, Koch, Regiomontanus, Porphyry, Campanus) divide each quadrant into three by different trisection rules and are distinct from whole-sign houses, where each sign is one whole place. In the medieval observational tradition the quadrant-instrument is the graduated 90° arc used to take altitude measurements for chart-casting before the era of programmatic ephemerides.

Historical Origin

Quadrant-based house systems (Porphyry's trisection of the quadrant) are attested in late-Hellenistic and medieval practice as alternatives to whole-sign houses; Placidus and Regiomontanus develop further trisection rules. The quadrant instrument is listed by Bonatti's *Liber Astronomiae* (13th c.) among the canonical medieval observational tools. The quadrant-developmental framing originates in late-20th-century CPA pedagogy (Sasportas), with Martin's *Mapping the Psyche* using quadrants as the finest-grained chart-shape sub-analysis.

Etymology

Origin: Latin. Meaning: From quadrans (a fourth part); literally 'a quarter.' Used both for the fourth part of a chart and for the 90°-arc measuring instrument..

Further Reading

• Clare Martin, Mapping the Psyche
• Howard Sasportas, The Twelve Houses
• Guido Bonatti, Liber Astronomiae