(Greek: nekros, corpse; manteia, divination)
Special mode of divination or seeking after knowledge of future or hidden things, by a evocation of the dead.
Found in every nation of antiquity, mentioned in the Bible and forbidden by the Mosaic Law, necromancy was a common practise among the pagans in the early Christian era.
It gradually became associated with alchemy, witchcraft, and magic, and was often known as the "black art" owing to a faulty derivation of the term from niger (Latin: black).
During the Middle Ages it was condemned by the Church; theologians held that necromancy is due to the agency of evil spirits, because the means taken are inadequate to produce the expected results.
It received a new impetus during the Renaissance by the revival of the Neo-Platonic doctrine of demons, and in recent times it has reappeared under the name of spiritism.
New Catholic Dictionary