Sol Invictus

Sol Invictus, the 'Unconquered Sun', was the official sun god of the later Roman empire, raised to special honor by the emperor Aurelian in 274, who made the Sun a chief god of the Roman state. In an age drawn increasingly toward a single supreme divinity, the Sun — visible, life-giving, sovereign over the heavens — offered a focus for a kind of imperial monotheism of light.

The cult absorbed the solar aspects of Helios, Apollo, and Mithras, and its festival of the Sun's rebirth at the winter solstice, around the twenty-fifth of December, was later overtaken by the Christian Christmas. The emperor Julian, in his Hymn to King Helios, gave this solar devotion its deepest philosophical form, identifying the worshipped Sun with the intelligible light that flows from the Good — the last great pagan theology of a world about to turn to a different Light.