The Immaculate Conception of Los Venerables

Murillo's Virgin stands on a crescent moon. Look at the horns of the moon: they face up, not down. A rival theological faction argued that they should face down (following the Book of Revelation). But Murillo followed the Franciscan tradition that the moon under Mary's feet was reflecting the sun above, and would therefore appear horns-up. It is one of the most subtle theological arguments made purely by lunar geometry in Western painting. The moon is on the wrong side because Murillo picked a side. Now at Museo del Prado, Madrid @museodelprado