Combust

Combustion is a debilitating condition in traditional astrology in which a planet falls within approximately 8° of the Sun's position, causing its light to be overwhelmed by the Sun's far greater radiance. The metaphor is astronomical: just as stars become invisible when the Sun is near them in the sky, a planet's independent significations are said to be burned up and weakened by solar proximity. William Lilly (Christian Astrology, 1647) described combustion as one of the most serious debilities a planet could suffer — the planet's testimony in a horary question was severely undermined, and matters it signified were unlikely to develop favorably. The condition is graduated: Lilly noted that a planet within about 8° is combust, but the effect increases as the planet approaches the Sun. Within 17 arc-minutes, the condition reverses entirely into cazimi (the heart of the Sun), the strongest fortification. The traditional distinction between combust and under the Sun's beams (within 17° but outside 8°) represents a milder version of the same principle: under the beams, the planet is weakened but not as severely as in combustion. Ptolemy and the Hellenistic tradition addressed this condition in terms of a planet's visibility. Demetra George (Ancient Astrology in Theory and Practice, Vol. I, 2019) provides a thorough synthesis of the classical sources on combustion, noting that context matters: a planet combust in its own sign, for example, may not be as weakened as one combust in an alien sign.