Complexion of the Planets (Complexio Planetarum)
Definition
The complexion of the planets is the medieval doctrine that reads each planet-pair joining for the specific things it produces in the world. Where one planet meets another, the combination yields its own trade, craft, body-trait, voice, or cultural signification, distinct from what either planet means alone. Bonatti arranges it as a grid: each of the seven planets is taken as the lead planet in turn and paired with each of the others, so Saturn-with-Jupiter, Saturn-with-Mars, and so on each carry a fixed joint meaning. The Latin complexio (mixing, tempering) renders the Greek krasis.
In Tradition
Across the Arabic-mediated Latin sources, the complexion doctrine holds that a planet's signification is reshaped by the planet it joins, so the practitioner reads pairs rather than single bodies. The lead planet sets the field and the partner steers it toward a particular craft or outcome: Saturn-with-Jupiter points to religious letters and divine writings, Saturn-with-Mars to ironwork, arms, and battles, Saturn-with-Mercury to the scribal crafts. Bonatti gathers these per-pair readings into per-planet chapters as a reference table.
In Practice
When two planets join in a chart, by conjunction, by aspect, or by sharing a sign, identify which one is the lead, then read the pair's joint signification rather than each planet on its own. Take Saturn as lead: Saturn-with-Jupiter gives the working of ecclesiastical letters and divine writings; Saturn-with-Mars gives iron, weapons, fire, blood, and strife; Saturn-with-Venus gives bells, drums, cymbals, and instruments; Saturn-with-Mercury gives white merchandise, parchment, and the craft of writing. Take Jupiter as lead: Jupiter-with-Saturn turns toward the science of the stars and surgical occupations; Jupiter-with-Sun toward disputes and zealous defence of orthodoxy. Use the pair to specify trade, profession, and bodily or temperamental signature when delineating occupation or character; weigh the condition and dignity of each planet to judge whether the joint signification comes out well or ill, and preserve the period's religious framings as historical material rather than endorsement.
Historical Origin
The doctrine reaches Latin Europe through Guido Bonatti's Liber Astronomiae (13th c., Tractate III), which builds the per-planet complexion chapters and cites earlier Arabic authorities including Masha'allah and Abu Ali al-Khayyat. It descends from the Hellenistic-Greek krasis (mixing) framing of joined planets, transmitted through the Arabic tradition. Robert Hand's Project Hindsight edition (1995) is the English source preserving Bonatti's per-pair catalogue.