It is maintained by Theosophists that these less evolutionarily developed beings have never been previously incarnated as human beings; they are regarded as on a separate line of spiritual evolution called the “deva evolution”; eventually, as their souls advance as they reincarnate, it is believed they will incarnate as devas. It is asserted by Theosophists that all of the above-mentioned beings possess etheric bodies (but no physical bodies) that are composed of "etheric matter", a type of matter finer and more pure that is composed of smaller particles than ordinary physical plane matter. (See the book "Occult Chemistry" by C.W. Leadbeater)