In occultism and demonology goetia (from Greek 'goeteia', witchcraft) is the art of invoking demons or other spirits and oblige them to do the conjurer's will without falling under their power.
The Ars Goetia, first part of The Lesser Key of Solomon, is a good example of treatise on this subject, but it was already known and explained in earlier times, in the Key of Solomon and other mediaeval grimoires.
