Placidus House System

Definition

Placidus is a way of dividing a chart into its twelve houses by time rather than by equal slices of sky — what astrologers call a quadrant system. It takes the path the Ascendant degree travels above and below the horizon, splits each half into three equal stretches of time, and projects those onto the zodiac. The Ascendant and Midheaven always land on the 1st and 10th house cusps. The houses come out unequal in size, varying with latitude, and the method breaks down above roughly 66.5 degrees of latitude.

In Tradition

Placidus is the most widely used quadrant house system in modern Western practice. It is classed as time-based — built from divisions of time — alongside the Koch and Topocentric systems.

In Practice

Astrologers choose Placidus when they want house cusps drawn from divisions of time. Part of why it became the most widely used quadrant system is simply that printed Placidus tables were easy to come by. Astrologers working at high latitudes may turn to other systems to avoid the distortions Placidus produces there. Primary Directions — a traditional timing technique — use the same path-of-the-Ascendant principle.

Historical Origin

Popularised by the Italian Benedictine monk Placidus de Titis in the 17th century. It displaced the previously dominant Regiomontanus system once Placidean tables became more widely available.

Etymology

Origin: Latin. Meaning: Named after Placidus de Titis, from Latin placidus, "calm, gentle.".

Further Reading

• Deborah Houlding, The Houses: Temples of the Sky
• Howard Sasportas, The Twelve Houses