ISIA, Ἰσία, feasts and sacrifices anciently solemnized in honour of the goddess Isis.—The Isia were full of the most abominable impurities; and for that reason, those who were initiated into them were obliged to take an oath of secrecy. They held for nine days successively, but grew so scandalous, that the senate abolished them at Rome, under the consulate of Piso and Gabinus. They were re-established by Augustus, and the emperor Commodus himself assisted at them, appearing among the priests of that goddess with his head shaven, and carrying the Anubis.
ISIACTABLE is one of the most considerable monuments of antiquity, discovered at Rome in 1525, and supposed by the various figures in bas relief upon it, to represent the feasts of Isis, and other Egyptian deities. There have been various opinions as to the antiquity of this monument: some have supposed that it was engraved long before the time when the Egyptians worshipped the figures of men and women. Others, among whom is bishop Warburton, apprehend, that it was made at Rome by persons attached to the worship of Isis. Dr Warburton considers it as one of the most modern of the Egyptian monuments, on account of the great mixture of hieroglyphic characters which it bears.