Sri Ramakrishna says in the Gospel of Sri Ramakrishna, "The body made of the five elements is the gross body. Mind, intellect, ego, and consciousness together form the subtle body. The body in which God's bliss is experienced and enjoyed is the causal body. The Tantras speak of 'the body of the Divine Mother.' Beyond all these stands the 'Great Cause' (Turiya)—beyond what words can tell." The five elements: earth or soil (which forms flesh, bone, and limbs), water (which forms blood and all liquid parts), air (which forms breath), fire (which forms the body's heat), and ether (which, based on the balance of the gross body's constituents, forms the mind and its nature).
The complete, undivided form of the gross, subtle, and causal bodies—this is called the human body. Whatever exists in this entire world, whether visible or invisible, whether inert, luminous, or conscious—all of it is manifest within the human body and human mind. Without some understanding of this, doubt and confusion may well arise in one from the very beginning of spiritual practice or the yogic path.
Form, shape, nature, bone, skin, fat, muscle, blood, vital fluids—these constitute the complete nature of the gross body. Perception, temperament, various luminous forms—these constitute the complete subtle body; consciousness and the power of consciousness, along with vital force, make up the causal body.
When one fully develops this human body through spiritual practice, one comes to see that the entire universe can be contained in one of the three forms of this body, and the whole manifestation of the world is fully expressed through these three bodies. So long as a human being does not perceive this cosmic development within oneself, one cannot find the foundation for the characteristic belief regarding this human body, nor can one offer any proof that the world, humanity, and God are fundamentally one. One can never demonstrate immortality through a mortal body.
Faith in the human body is the true, natural foundation, and feeling is its guide.
Upon these two must one rely in treading the paths of worship, austerity, spiritual practice, and yoga. The provisions for the journey are the grace of the guru and the methods or techniques taught by the guru. For the immortality of the causal body is true immortality, and through action, humans are capable of achieving even that. Whether today or tomorrow, this hope will surely be fulfilled in humans if they continue their effort.
What is the need for the gross body? The gross body is the body of action. We perceive the full development of the causal and subtle bodies through the awareness afforded by the gross body. Where the gross body is absent, how can perception and awareness unfold? Therefore, if one wishes to see the causal and subtle fully expressed through action, there is no other body or external vehicle besides the gross body, for only through the gross body can we know, understand, and perceive the subtle and causal. Without the gross body, this would be impossible in any way. It is through form, shape, appearance, and qualities—through perception itself—that we are able to apprehend or grasp the formless essence and supreme consciousness through action or movement.
Through the subtle or sentient body, we perceive and grasp all manner of visible and invisible forms and configurations. This is the body suffused with feeling, with consciousness. It is through this subtle body that man accomplishes the full expansion of intellect and knowledge. Within this sentient body, we naturally witness the complete expression and unfoldment of the active body; it is the middle body among the three—from here flows the work of creation, sustenance, and dissolution, and this body alone seems to maintain the harmony and equilibrium of the other two, dwelling eternally in man's being by virtue of his nature.
As the gross body is action-dominated, so the subtle body is consciousness and mind-dominated. Yet, to speak truly, action itself is the governing force of all things. Its primacy exists equally in all bodies.
For the causal body or the life-principle holds the other two bodies within itself. From this source flows the complete unfoldment of both gross and subtle bodies. Because the causal body is consciousness-dominated, it may be called the true root of creation itself. Without the causal body, the active or working body cannot even manifest. And if action were devoid of consciousness, the sentient or knowing body could not arise; and if the knowing body—the veil of intellect—does not develop, there is no way whatsoever to grasp the luminous or conscious body.
Therefore, one may say that the causal body or the consciousness-filled body is the very root of all creation. From here man finds the path toward Brahman, toward God, toward devotion and love. Until he reaches here, man can in no way discover the source of those paths.
Thus, from the causal flows the full manifestation of both gross and subtle; and on the other side, the complete unfoldment of God, Brahman, and love.
Now we see: what exists in the causal body as atoms, exists in the subtle as molecules, and in the gross as form, configuration, and nature. Therefore, only through the seamless union of these three does the full and complete unfoldment of man become possible. It is clear without doubt or difficulty that any two without the third remain incomplete.