When Joseph dreams in Genesis of sun, moon and stars bowing to him, his father instantly reads the sun as himself: the equivalence of sun with father and king was already proverbial in the ancient Near East, where kings took the sun as title and emblem, and the Greek dream handbooks worked the same rule, reading the heavenly bodies as the powers over the dreamer's life and the sun as the greatest of them. A rising, shining or darkened dream sun was read as the fortune of the father, the patron or the throne.
Religious history gave the sun a second identity as the image of divinity itself, from Ra and Shamash through Apollo to the sun metaphors that Christianity applied to Christ, and philosophy followed, Plato making the sun the visible stand in for the Good. The alchemists sealed the inheritance for the modern psychologies by making sol the gold making principle, the conscious, formative, kingly pole of the work.
Jung took the alchemical sun over explicitly: in his tradition the sun is consciousness itself, the ego's daylight, the hero whose nightly descent and dawn return is the oldest pattern of renewal, and a dream sun's condition, brilliant, clouded or black, is read as a report on the dreamer's conscious standing. The black sun of the alchemists, sol niger, serves that school as the image of consciousness eclipsed. Popular dictionaries compress the lot to vitality and success; the lineage behind the compression is the point of this entry.