Θεωρία, a name which the ancients gave to that sacred part of magic which we sometimes call white magic, or the white art.

The word is formed from ὁράω, "God;" and ἔργον, "work;" q. d. the art of doing divine things, or things which God alone can do; or the power of working extraordinary and supernatural things, by invoking the names of God, saints, angels, &c. Accordingly, those who have written of magic in general, divide it into three parts: the first whereof is called theurgy, as operating by divine or celestial means; the second, natural magic, performed by the powers of nature; and the third, comprehending necromancy, sorcery, and witchcraft or magic, performed by the assistance of demons or departed men. See Magic.