Triplicity Decans

Definition

Triplicity decans are an alternative way of assigning decan-rulers: each decan goes to one of the three triplicity-rulers of the sign's element. In a fire sign such as Aries, the first decan (0-10°) is ruled by Mars as the home-ruler of Aries, the second (10-20°) by the Sun as the home-ruler of Leo, and the third (20-30°) by Jupiter as the home-ruler of Sagittarius — spreading the three same-element home-rulers across the three decans of each sign in that element. This is a different scheme from the Chaldean-order face-rulership system.

In Tradition

In the comparative-rulership doctrine treated by Lilly's Christian Astrology I and the Bonatti Liber Astronomiae body of work, the triplicity-decan convention is one of two competing decan-rulership systems, set beside the Chaldean-order face-system. Lilly keeps the Chaldean-order faces as the standard medieval-Latin essential-dignity tier, while the triplicity-decan convention lives on in the parallel Indian-Vedic drekkana practice. Modern Western practitioners such as Coppock treat both as side-by-side doctrines, each suited to a different magical or interpretive framework.

In Practice

You choose the convention on purpose: for medieval-Latin essential-dignity grading, use the Chaldean-order faces (Lilly's +1 dignity point); for studying how a placement resonates with its element, or for staying in step with the Indian-Vedic drekkana technique, use triplicity decans. To assign by triplicity decans, you (1) identify the sign's element — fire, earth, air, or water; (2) list the three signs of that element in cardinal, fixed, mutable order — fire gives Aries, Leo, Sagittarius; (3) hand the three signs' home-rulers (Mars, Sun, Jupiter) to the first, second, and third decan in turn. This scheme leans on the element's inner cardinal-fixed-mutable cycle rather than the heptazone speed order of the planets, and it is especially useful for reading a placement against that threefold expression of its element.

Historical Origin

Triplicity-decan rulership survives in the classical Indian astrological corpus — the Brihat Parashara Hora Shastra and its parallel drekkana scheme — and was used in some medieval Latin sources alongside the dominant Chaldean-order face-system. Lilly's Christian Astrology I (1647) records the Chaldean-order convention as primary while noting that alternatives exist. Modern practitioner-revival treatments appear in Coppock's 36 Faces (2014) and in Hand-school traditional-revival practice.

Further Reading