Physiology considers man as a physical structure with a brain, having the capacity to think and feel. It is well known that mere physical body will not move, grow, or act, unless the Life-principle presides over it. A dead body can no more smile, eat or walk, think or feel. This is true, however great the man might have been while he was alive. This divine Spark-of-Life is called the Atman in Vedanta.

The Five Sheaths (Pancha Kosam)

The Atman is considered to have been enveloped by the various layers of matter of varying degrees of grossness. There are 5 distinct sheaths :

1. the Food sheath, the outermost. (Annamaya kosam)
2. the Vital-Air sheath, lining it internally. (Pranamaya kosam)
3. the Mental sheath within; and still interior. (Manomaya kosam)
4. the Intellectual sheath; and lastly. (Vijnanamaya kosam)
5. the Bliss sheath, the subject of all. (Anandamaya kosam)

When we say that one sheath is interior to the other, it only means that the inner one is subtler than the outer. Again, the subtlety of a sheath is measured by its pervasiveness. For example, water is subtler than ice, steam is subtler than water and so on.

The subtlest of all is the Life-centre in us, which is the core of this five-sheathed structure. These five layers of matter , along with the eternal Life-centre at its core, together constitute the spirituo-physical structure of every person.

The Food and the Vital-Air sheaths together constitute the gross body. The Mental and the Intellectual sheaths constitute the subtle body. The Bliss sheath is called the causal body. Of these, it is the subtle body that is the instrument for all seekers in obtaining Self-perfection.

Mind is the doubting element, while Intellect is the determining factor in each of us.

The Kosa or Sheath is compared to the scabbard. The scabbard of the sword covers the sword. It is of the same shape as the sword. It indicates the presence of the sword , even though it covers the sword from one's sight. The scabbard is always different from the sword and does not affect the sword in any way. Similarly, the Self is covered by the five sheaths. The functioning of these sheaths proves the presence of the Self. But they cover the true nature of the Self.

What is the mind ?

 This is better understood if we take the example of a river. The river is not water, nor is it water with two banks. A river is there where waters flow, the flowing is the essence of the river.

 Similarly, thoughts are not the mind. But thoughts flowing one after another in an unbroken continuity create a delusory 'something' called the mind. And this mind threatens us, nay, even governs over us, persecuting us with its low demands, animal instincts, and vicious urges, or, at some moments with its higher demands of divine calls and spiritual urges.

To control and develop this mind and bring it within our hold is the secret of all personality development. He who is a master of his mind, is a master of the world.

Mastery over the situations in life, without a mastery over the mind, would be a mere vain dream. And this is the great secret of the failure of man today, as individuals or communities or nations in the world. The tragedy of man is the tragedy of the condition of his mind.

Mental control means the control of the thought flow. When thoughts are least agitating in us, we are in the state of maximum happiness. The more the stormy flood of gushing thoughts, the more disturbed the mind becomes. Calm the mind through a process of stilling its thoughts. But the 3 knots - Ignorance, Desire and Action - make this process very difficult.

Man is ignorant of his real spiritual identity. Because of his ignorance, he feels himself imperfect. Revolt against this sense of imperfection manifests itself as desires in the mental zone. Desires throw open the volcano- peaks of the mind and they erupt to throw out the scorching lava of thought-currents. Without desire, no thoughts can rise up. When a desire gets fully established in the mind, the very desire in self-expression manifests as our actions in the outer world.

Thus, ignorance at the spiritual level itself is the desire rising in the mental zone, and the desires are amplified in the grosser sense-world of objects, as our actions express themselves in the quality and nature of their desires, which in their turn advertise the degree and depth of ignorance.

The attempt of every religion is to eliminate ignorance through spiritual practices until the devotees come to gain the Light of Wisdom. The ignorance in man, manifesting as desires in his mental plane, comes out into the world as actions. The Great Saints, therefore, advise all seekers, first of all, to purify, control and regulate the texture of their actions. " Be good, be kind, be tolerant, be merciful, be selfless"- are some of the advices common in all great religions of the world.

When actions are thus controlled and purified, they being but expressions of the thoughts of the actor, those thoughts get themselves purified. Since thoughts are generated by desires, the pure thoughts, naturally, propel pure desires. The pure desires will gradually remove the spiritual ignorance and Eternal Knowledge will come to shine and the processes of evolution will reach their last destination- Perfection.

Since Personality consists of several sheaths, the body being only the outermost, there is no reason why Personality should die when the body is shed. The Sages of the Upanishads saw Personality as a field of forces. Packets of Karma to them are forces that have to work themselves out. If the process is interrupted by death, these forces remain until conditions allow them to work again in a new context.

Again, sleep can illustrate the dynamics of this idea of reincarnation.In sleep a person passes in and out of two stages - dreaming and dreamless sleep. In the first, consciousness is withdrawn from the body and senses, but still engaged in the mind. In dreamless sleep, however, consciousness is withdrawn from the mind as well. Then the thinking process - even the sense of " I " - is temporarily suspended, and consciousness is said to rest in the Self. In this state a person ceases to be a separate Personality. In dreamless sleep, the Upanishads say, a king is not a king nor a pauper poor, no one is old or young, male or female, educated or ignorant. When consciousness returns to the mind, however, the thinking process starts up again, and Personality returns to the body.

According to this analysis, the ego dies every night. Every morning we pick up our desires where we left off; the same person, yet a little different too. The Upanishads describe dying as a very similar process. Consciousness is withdrawn from the body into the senses, from the senses into the mind and finally consolidated in the ego. When the body is finally wrenched away, the ego remains - a potent package of desires and karma. And as a person's last waking thoughts shape his dreams, the contents of the unconscious at the time of death - the residue of all that he has thought and desired and lived for in the past - determine the context of his next life. He takes a body again to come back to just the conditions where his desires and karma can be fulfilled. So, there is a continuity between this life and the next, and all the baggage of desire and motivation goes right along with the soul.

The Self-realized person, however, has no karma to work out, no personal desires; at the time of death he is absorbed into the Lord. Such a person, the Upanishads stress, can actually shed his body voluntarily when the hour of death arrives, by withdrawing consciousness step by step in full awareness. Some of the Gita's most fascinating verses are Krishna's instructions on how to die (8:9-14). Bhagavat Gita-Chapter 8