Etheric plane
The etheric plane (see also etheric body) is a term introduced into Theosophy by Charles Webster Leadbeater and Annie Besant to represent the subtle part of the lower plane of existence. It represents the fourth [higher] subplane of the physical plane (a hyperplane), the lower three being the states of solid, liquid, and gaseous matter. The idea was later used by authors such as Alice Bailey, Rudolf Steiner, Walter John Kilner and others.
The term aether (also written as "ether") was adopted from ancient Greek philosophy and science into Victorian physics (see Luminiferous aether) and utilised by Madame Blavatsky to correspond to akasha, the fifth element (quintessence) of Hindu metaphysics.
The Greek word aither derives from an Indo-European root aith- ("burn, shine"). Blavatsky also related the idea to the Hindu Prana principle, the vital, life-sustaining force of living beings, present in all natural processes of the universe. Prana was first expounded in the Upanishads, where it is part of the worldly, physical realm, sustaining the body and the mind. Blavatsky also tended to use the word "astral" indiscriminately for these supposed subtle physical phenomena. The esoteric concepts of Adi, the Buddhic plane, the causal plane, and the monadic plane are also related to that of the etheric plane.
