Now I will take you to the most wonderful mental factory. It is very close to you; it is a wonder of wonders. Even a rank materialist, if he is very sincere, will be turned into a perfect theist, instantly, if he closes his eyes for a moment and seriously reflects on the working of this marvellous factory. The Kena Upanishad opens with the following lines: "Who is the Director of this mind? Who gives Light and Power to this mind?" It goes on "Brahman is the Mind of minds, the Prana (life) of pranas, the Eye of eyes, the Ear of ears."
What a bold philosophy. At once it raises man to an unerring solution for all the different problems of life. The four mahavakyas (great utterances): "Prajnanam brahma" (consciousness is the Absolute); "aham brahma asmi" (I am the Absolute); "tat twam asi" (that thou art); "ayam atma brahma" (the Self is the Absolute), infuse power and joy into the hearts of all hearers. They produce drastic changes in your life. Then you will laugh at the vain pomp, the empty glory and the artificial and miserable life of a rich man.
The eyes and the ears are the gate-keepers of this mental factory - they are the `way in' and mouth is the `way out'. Eyes and ears bring inside the mental factory matters for manufacture. Light and sound vibrations are brought inside through these two avenues.
First of all they are made into `percepts' by the mind. They are then presented to the intellect. The intellect converts these `percepts' into `concepts' or ideas. These ideas are expressed by the outside gatekeeper, the organ of speech.
The external physical eyes and ears are mere instruments. But the real visual and auditory centres are in the brain and in the astral body - these are the real senses. Understand this point well. The intellect receives these materials from the mind and presents them to the purusa or Atman (the Self), who is behind the screen.
The mind is the head clerk of this mental factory. He has ten clerks, the five jnana indriyas (senses) to bring news from the facts outside. The facts are placed by the mind before the intellect, who places them before the purusa (inner self). A message comes back from the purusa to the buddhi (intellect). Buddhi decides and determines, and then gives the answer back to the mind, for execution. The five karma indriyas (organs of speech, hands, feet, genitals and anus) execute the order of the mind who is their master.