One should identify Brahman neither with the head nor with the middle part nor with the bottom but with (what remains in the shape of) the tail, since it is said that Brahman is ‘the Tail’ and substratum. Thus those who contemplate this fourfold division attain the supreme Goal.
~ Verse 5
Acharya Prashant: Brahman is to be identified with no part of the body but with the tail. What is meant by that? The idea is that the tail has only one function - to give stability. Brahman is the stabilizing tail of the universe. All other parts of the body have various utilities and functions. But the tail gives stability.
So it is being said that similarly, the body of the universe or the body of the man or the person of man finds stability only in Brahman. That is what Brahman does - give him (man) stability. Otherwise, he will perform all actions possible to the body and yet remain unstable. And what does unstable mean? Restlessness, suffering, chaotic; not in equilibrium; moving from here to there; not finding peace anywhere.
The function of Brahman is to give stability.
Questioner: What does it mean by ‘Thou art That’ (You are That)?
AP: You think of yourself as so many things and everything has a name. But it is being asserted that your real self is revealed when you are no more attached to these things. Things have names. So whenever do you have an attachment to a thing, then your identity statement is – You are ‘a’, ‘b’, ‘c’, ‘father’, ‘employee’, ‘son’, ‘husband’, ‘fast’, ‘slow’, ‘high’, ‘low’. Then you can talk of yourself as I am all these things- ‘a’, ‘b’, ‘c’ and the rest of things. But with attachment and identification with respect to object gone, you cannot talk of ‘a’, ‘b’, ‘c’ and all. Then you can only indicate towards an emptiness. Because emptiness is to be given some name. So it is said ‘That’; ‘You are That.’ You are neither ‘a’, nor ‘b’, nor ‘c’, not ‘Tom’, nor ‘Ram’, just ‘That’.
It could also have been said ‘You are’. Full stop. ‘You are…silence’. So here that should be read as silence.
When it is said that, ‘You are That’, “ Tat tvam asi (तत् त्वम् असि )”, that ‘*Tat*’ means nothing in particular. Do not think that it has some objective existence. Do not think that you can have an idea of it, or look at it, or touch it, or dream of it, or reach it. All those things you anyway keep doing and planning of doing as a person. And if that becomes another object, then you remain the person you are. The whole declaration, that ‘You are That’ is about telling you that you are not really the person who you have assumed yourself to be.
So, it’s an invitation to be more careful about yourself, to re-investigate, to look at your face with more clean and open eyes, that’s what it is saying- ‘You are That.’ You are not Sandeep (addressing to the listener). It would have been very easy to say that you are Sandeep, and then no inquiry is needed.