To understand how we may develop our spiritual life through service, we first have to know who we truly are. The Upanishads teach us that we are not limited individuals consisting of a body and a mind, but divine in the core of our being. Our divine essence, called the Atman, is the eternal source of all purity, strength, bliss, and fulfillment. Being ignorant of this truth, we identify ourselves with our body and mind, and seek lasting peace and happiness in ephemeral objects. After having our share of pleasure and pain from the world, we perceive the futility of worldly pursuits. We then appreciate the teaching of the Lord in the Bhagavad Gita: "Having come to this transitory, joyless world, worship Me (9:33)." True religion begins when we respond to that call, develop longing for God, and worship Him.
According to the Taittiriya Upanishad, we have five different selves. These selves are the result of our identification with the five layers of our personality. The Atman, our real "I", is imprisoned, as it were, in these five layers. Self-realization amounts to de-identifying our true "I" with them.
1. Physical self: We are the physical self when we identify with our body. The world and its objects are real to us in this state. We look upon ourselves and others as a man or woman, young or old, dark or fair, and think and act accordingly.
2. Energy self: Subtler than the physical self and pervading it is the energy self. Usually called the life breath, it is responsible for the functions of breathing, assimilation of food, excretion, circulation of blood, and the exit of the life breath from the body at death. It activates our hidden mental impressions, which influence our thoughts and actions. In the dream state, it stimulates the mental impressions that create dreams.
3. Mental Self: The mental self is subtler than the energy self and pervades it. As mental selves, we identify with the mind's conflicting desires and emotions. Due to association with the mental self, we are tossed about by the varying states of the mind like happiness, calmness, tranquility, misery, confusion, frustration, and uncertainty.
4. Intelligence self: The intelligence self is subtler than the mental self and pervades it. When we identify with buddhi, or the higher mind, we are the intelligence self. Our sense of judgment, decision making, discrimination, and righteous living stem from the intelligence self. Identified with buddhi, we are able to exercise self-control and discipline our wayward mind.
5. Blissful self: The blissful self is subtler than the intelligence self and pervades it. As blissful selves, we are detached from the other four layers of our personality and abide close to the Atman, only removed from it by a fine screen of ignorance. Because of its proximity to the Atman, this self is the source of bliss, unfiltered through the body, mind, and senses. We abide as the blissful self in deep sleep. We are then one with the bliss of our true Self, but are not conscious of it. In the waking state we are the blissful self when we experience joy, for instance, while being totally absorbed in elevating music or a work of art. Consciously abiding as the blissful self in the waking state denotes a state of high spiritual realization, devoid of any attachment to body and mind.
The goal of spiritual quest is to go beyond all five selves and abide as the Atman.