The human body, composed of seven billion billion billion atoms, is often compared to a machine in that it has an engine, electrical system, movable parts, and a computer on board. Such an analogy ignores four essential body aspects. Ancient as well as contemporary literature has explored human consciousness, spirituality, and the concept of a soul. Within this exploration has been the following four generally non-visible body energy fields: the etheric body, astral body, mental body, and the causal body.
The etheric body, sometimes referred to as the ether-body or aether-body, is the first layer of the human energy field. It provides vitality and life to the physical body. It encompasses electromagnetic, chi, prana, and or Ki vitality. From a science viewpoint, it is composed of subatomic particles. The etheric body also attunes ones consciousness to universal energy. Blue-violet color radiates from the etheric body. The etheric body is the same shape as the physical body.
Next is the astral energy field and it is generally posited between the mental and causal body energy fields. The idea dates back to at least the time of Plato. Some writers claim it is the spiritual counterpart of the physical body; however, Theosophists indicate the astral body is the link between the human nervous system and the cosmos. The astral body is an exact replica of the physical body and is the instrument of emotions. Like the other generally non-visible body energy fields, it extends beyond the actual physical body. Astral projection utilizes the astral body to travel to other dimensions. Finally, the astral body is a field of energy occupying the same space as the aura, but appears to have a higher degree of flexibility in that it is constantly reshaped by thought and emotion. The astral energy field functions as a vehicle of consciousness, which can exist separately from the physical body even though it is connected to that physical body.
The third body energy field is called the mental body. It presents an interesting challenge particularly in view of the quarrel over the location of the mind. It is believed this mental body energy field is located in the mind. Further, this field is the vehicle of thought vibration and enables the manifestation of the self. Healing at this energy field is stronger, longer lasting than the other three body energy fields. The reason for this is the suspicion that the mind energy field is all encompassing, that is, it exists everywhere in the human physical body
The causal body is the fourth body energy field. It has its roots in Yogic and Vedantic concepts that have been forged into some of the basic principles of Theosophy, esotericism, and spiritual mysticism. It is here that the soulthe spiritual soul that survives the physical death of the body, exists. Since the soul is energy and if one accepts the major premise of the Second Law of Thermodynamics that energy cannot be destroyed, it makes sense then, that the soul survives the death of the body.