His form is not to be seen. No one can see Him with the eye. He is perceived by the heart, by the intellect and by the mind. They who know this become immortal.
The Supreme, being formless, cannot be discerned by the senses, hence all knowledge of Him must be acquired by the subtler faculties of heart, intellect and mind, which are developed only through the purifying practice of meditation.
X
When the five organs of perception become still, together with the mind, and the intellect ceases to be active: that is called the highest state.
The teacher now shows Nachiketas the process by which the transcendental vision can be attained. he out-going senses,—seeing, hearing, smelling, touching, tasting; the restless mind and the intellect: all must be indrawn and quieted. The state of equilibrium thus attained is called the highest state, because all the forces of one's being become united and focused; and this inevitably leads to supersensuous vision.
XI
This firm holding back of the senses is what is known as Yoga.
Then one should become watchful, for Yoga comes and goes.
Yoga literally means to join or to unite the lower self with the Higher Self, the object with the subject, the worshipper with God. In order to gain this union, however, one must first disunite oneself from all that scatters the physical, mental and intellectual forces; so the outgoing perceptions must be detached from the external world and indrawn. When this is accomplished through constant practice of concentration and meditation, the union takes place of its own accord. But it may be lost again, unless one is watchful.
XII
He cannot be attained by speech, by mind, or by the eye. How can
That be realized except by him who says "He is"?