In early theosophical literature the term "astral" may refer to the aether. Later theosophical authors such as Annie Besant and C. W. Leadbeater make the astral finer than the etheric plane but "denser" than the mental plane. In order to create a unified view of seven bodies and remove earlier Sanskrit terms, an etheric plane was introduced and the term "astral body" was used to replace the former kamarupa - sometimes termed the "body of emotion, illusion or desire". Some of those propounding such claims explain their belief that letting go of desires is spiritual progress by noting that, the more one lets go of earthly 'desire' feelings, the less tied down to the physical world, a world of illusion, and the more connected to the astral, where all is visible and known.