This body is made of particles which we call matter, and it is dull and insentient. So is what the Vedantists call the fine body. The fine body, according to them, is a material but transparent body, made of very fine particles, so fine that no microscope can see them. What is the use of that?

It is the receptacle of the fine forces. Just as this gross body is the receptacle of the gross forces, so the fine body is the receptacle of the fine forces, which we call thought, in its various modifications. First is the body, which is gross matter, with gross force. Force cannot exist without matter. It must require some matter to exist, so the grosser forces work in the body; and those very forces become finer; the very force which is working in a gross form, works in a fine form, and becomes thought.

There is no distinction between them, simply one is the gross and the other the fine manifestation of the same thing. Neither is there any distinction between this fine body and the gross body. The fine body is also material, only very fine matter; and just as this gross body is the instrument that works the gross forces, so the fine body is the instrument that works the fine forces. From where do all these forces come?

According to Vedanta philosophy, there are two things in nature, one of which they call Âkâsha, which is the substance, infinitely fine, and the other they call Prâna, which is the force. Whatever you see, or feel, or hear, as air, earth, or anything, is material — the product of Akasha. It goes on and becomes finer and finer, or grosser and grosser, changing under the action of Prana.

Like Akasha, Prana is omnipresent, and interpenetrating everything.  Akasha is like the water, and everything else in the universe is like blocks of ice, made out of that water, and floating in the water, and Prana is the power that changes this Akasha into all these various forms. The gross body is the instrument made out of Akasha, for the manifestation of Prana in gross forms, as muscular motion, or walking, sitting, talking, and so forth.

That fine body is also made of Akasha, a very fine form of Akasha, for the manifestation of the same Prana in the finer form of thought. So, first there is this gross body. Beyond that is this fine body, and beyond that is the Jiva, the real man. Just as the nails can be pared off many times and yet are still part of our bodies, not different, so is our gross body related to the fine.

It is not that a man has a fine and also a gross body; it is the one body only, the part which endures longer is the fine body, and that which dissolves sooner is the gross. Just as I can cut this nail any number of times, so, millions of times I can shed this gross body, but the fine body will remain. According to the dualists, this Jiva or the real man is very fine, minute.

Swami Vivekananda

To be continued ...