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.
Blavatsky also related the idea to the Hindu Prana principle,[1] 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.
[4] Similarly, according to the Rosicrucian writings of American occultist and mystic Max Heindel[5] there is – in addition to the solids, liquids, and gases which compose the Chemical Region of the Physical World – a finer grade of matter called ether that permeates the atomic structure of the earth and its atmosphere.