There seems to be a battle like that of the gods and the giants going on among them, because of their disagreements about existence […] Some of them drag down everything from heaven and the invisible to earth, actually grasping rocks and trees with their hands; for they lay their hands on all such things and maintain stoutly that that alone exists which can be touched and handled; for they define existence and body, or matter, as identical, and if anybody says that anything else, which has no body, exists, they despise him utterly […] those who contend against them defend themselves very cautiously with weapons derived from the invisible world above, maintaining forcibly that real existence consists of certain ideas which are only conceived by the mind and have no body. (Sophist)
