Taurus — 2nd Decan (10°–20°)
The second decan of Taurus covers 10° to 20° of the sign. Triplicity indicates Mercury as ruler; the Chaldean system indicates the Moon — two different rulers, each imprinting a particular tone on Taurus' base nature.
Last reviewed: 2026-07-20
Historical fact
The decan system dates back to Ancient Egypt, where 36 small constellations — the decans — were observed rising successively on the night horizon at roughly ten-day intervals, serving as a star calendar recorded on coffin lids and astronomical tables as early as around 2100 BCE. That system's merger with the Babylonian-derived 12-sign zodiac only happened in the Hellenistic period, when Greek astronomers began dividing each sign into three 10° decans. In this second decan of Taurus, Triplicity and the Chaldean system disagree again: one indicates Mercury, the other, the Moon.
Interpretation — Triplicity System (Modern Astrology)
Under Triplicity, the second decan of any Earth sign is ruled by the next same-element sign's ruler — for Taurus, that's Mercury, ruler of Virgo. The reading combines Taurus' sensory stability and attachment to material security with Mercury's typical attention to detail, practicality and analytical capacity, resulting in a more meticulous, results-oriented Taurus.
Interpretation — Chaldean System (Hellenistic Tradition)
In the Chaldean system's continuous cycle, the Moon rules this decan. The combination adds a layer of emotional sensitivity, protective instinct and need for comfort to Taurus' base nature — the sign's drive for material security here gains a more affective component, tied to memory, home and caretaking.
This section presents one tradition's interpretation, not a verifiable fact.
Frequently asked questions
- Why does Taurus' 2nd decan have different rulers in each system?
- Because Triplicity and the Chaldean system follow distinct assignment logics: the former cycles through same-element signs (here, Mercury from Virgo), while the latter follows one continuous, unbroken sequence of the 7 classical planets (here, the Moon). The two only coincide occasionally.
- What changes between Taurus' 1st and 2nd decan?
- The 1st decan, ruled by Venus under Triplicity, is Taurus' purest expression. The 2nd, ruled by Mercury under Triplicity and by the Moon under the Chaldean system, adds a more analytical or more emotional layer, depending on which system you consult.
Sources
- Nicholas Campion. A History of Western Astrology (2009).
- Claudius Ptolemy. Tetrabiblos (c. 150).
- Vettius Valens. Anthology (Hellenistic astrology) (c. 175).
- Otto Neugebauer, Richard A. Parker. Egyptian Astronomical Texts (1960).