The Septenary in Helena Blavatsky's teachings refers to the seven principles of man. In The Key to Theosophy she presents a synthesis of Eastern and Western ideas, according to which human nature consists of seven principles. These are:
Atma - Spirit or Self - one with The Absolute as Its Radiation.
Buddhi - Spiritual Soul - vehicle of pure universal spirit.
Manas - consisting ofHigher Manas, the spiritual, inner, or higher Ego; and Lower Manas, the ordinary mind.
Kamarupa - the "desire body", seat of animal desires and passions.
The first body is called sthula-sarira. A gross body, impermanent because of its wholly compound character. The physical body is usually considered as the lowest substance-principle. The physical form is the result of the harmonious co-working on the physical plane of forces and faculties streaming through their astral vehicle or linga-sarira, the pattern or model of the physical body.
The second body is called Linga-Sarira,. A pattern or model that is impermanent; the model-body or astral body, only slightly more ethereal than the physical body. It is the astral model around which the physical body is built, and from which the physical body flows or develops as growth proceeds.
The third body is prana. In Theosophy, the breath of life. This life or prana works on, in, and around us, pulsating unceasingly during the term of physical existence. Prana is "the radiating force or Energy of Atma – as the Universal Life and the One Self – its lower or rather more physical, because manifesting, aspect. Prana or Life permeates the whole being of the objective Universe; and is called a 'principle' only because it is an indispensable factor and the deus ex machina of the living man."
The fourth principle is kāma. Desire; the desire principle is the driving, impelling force. Born from the interaction of atman, buddhi, and manas, kama per se is a colourless force, good or bad according to the way the mind and soul use it. It is the seat of the living electrical impulses, desires, and aspirations, considered in their energetic aspect.
The fifth principle is manas. The seat of mentation and egoic consciousness; in humanity Manas is the human person, the reincarnating ego, immortal in essence, enduring in its higher aspects through the entire manvantara. When embodied, manas is dual, gravitating toward buddhi in its higher aspects and in its lower aspects toward kama. The first is intuitive mind, the second the animal, ratiocinative consciousness, the lower mentality and passions of the personality.
The sixth principle or vehicle is Buddhi. The vehicle of pure, universal spirit, hence an inseparable garment or vehicle of atman, which is, in its essence, of the highest plane of akasa or alaya. In man buddhi is the spiritual soul, the faculty of discriminating, the channel through which streams divine inspiration from the atman to the ego, and therefore that faculty which enables us to discern between good and evil: spiritual conscience. The qualities of the buddhic principle when awakened are higher judgment, instant understanding, discrimination, intuition, love that has no bounds, and consequent universal forgiveness.
The seventh is called Atman. Self; pure consciousness, that cosmic self which is the same in every dweller on this globe and on every one of the planetary or stellar bodies in space. It is the feeling and knowledge of "I am," pure cognition, the abstract idea of self. It does not differ at all throughout the cosmos except in degree of self-recognition. It may also be considered as the First Logos in the human microcosm. During incarnation the lowest aspects of atman take on attributes, because it is linked with buddhi, as the buddhi is linked with manas, as the manas is linked with kama, etc.
Despite using Sanskrit terminology, many of these concepts are expressed differently from their Indian counterparts. The Atman or Self in monistic Vedanta for example is considered the Universal Self that is the same as, and not just a "ray" of, the Absolute or Brahman. These seven principles can be grouped into a threefold division of Monad, Ego and Lower Quaternity. In this, the Lower Manas is a transitional principle, the soul so to speak, which can choose to join either with the Kama principle to form the "Kama-Manas", which becomes an "elementary" or "astral" spirit after death, or link with the higher or Buddhi principle to form a higher spiritual consciousness, the "Buddhi-Manas". Theosophists believe that the most material of the vestures of the soul are interpenetrated by the particles of the more subtle vesture. The Sthula Sarira or gross physical body is mostly space at its atomic level, as all matter is known to be. The interstitial space is inhabited by the subtler particles of the Astral body or Linga sarira, and so on for the other more energy-like envelopes of the Soul. Because of the interpenetration of each sheath the so-called inner person is a fluid and unbroken continuity, although varying in density/flexibility and energy. Therefore, it is progressively more susceptible to its true spiritual nature as it is progressively less encumbered by material boundaries; the image of a suspension or colloid in chemistry is a similar perspective. Matter is postulated to be the physical counterpart of consciousness ; the interpenetration of sheaths allows for consciousness to interpenetrate man's nature and is a Theosophical explanation of sensory experience. As well as seven subtle bodies, there are also seven Cosmic planes of existence. However, in Blavatsky's teachings, the Planes and Principles don't match up. While undergoing some changes and modifications in the hands of later esotericists such as C.W. Leadbeater, Rudolf Steiner, and Alice Bailey, Blavatsky's description of the seven bodies or principles remained a central part of western esoteric and New Age thinking ever since.