‘Shad‘ is to sit down; settle down; not moving here or there; up or down and this way or that way. Sitting down of the mind is what makes the mind receptive to receive the ‘Truth,’ as and when the teacher conveys it.
Now, let’s go back to the middle syllable we kept for later–’Ni‘.
‘Ni‘ is the syllable that indicates the level at which the student sits with the teacher. ‘Ni‘ is the root of the Hindi word ‘niche’ meaning ‘down’. So, ‘Ni‘ indicates that the student is sitting down, which also means the student is considering. It is not a physical thing. It is not as if the teacher is sitting up, high up there on a seat and the student is sitting on the floor. No, that is not what we are talking about.
We are talking about the mental attitude of the student–who knows that he does not know and, therefore, is keeping his mind open to understand that which he hasn’t understood till now. Like an open vessel; like an empty vessel that is ready to receive.
If you keep the vessel at a higher position and try to pour something into it from below, nothing will stay there. The vessel has to be kept below and whatever it is has to be poured from above. In the same way, ‘Ni‘ indicates the humility of the student who sits with the understanding that he does not know or he is now moving into an unexplored territory that cannot be found either by his senses or by his mind.
Therefore, the student, without prejudice, is sitting down with an open mind to receive the teachings of the ‘Truth’ from the teacher who is seated close to him. The student, whose mind is now settled down and has become quiet, is in a position to receive that, which is being given.
If you keep the vessel at a higher position and try to pour something into it from below, nothing will stay there. The vessel has to be kept below and whatever it is has to be poured from above.
Now, any teaching that takes place this way, any relationship between the student and the teacher that takes place this way, can be called the teaching of the Upanishad. According to me, there is no need for it to necessarily come from a particular set of books or scriptures.
Whenever a sincere student, a Satya Kama–one who searches for nothing but the ‘Truth’–sits in humility before a teacher, with his mind open and unprejudiced, ready to receive that which is given–that kind of learning and whatever is learnt in that kind of teaching is considered the Upanishad, the ‘Truth’.
The entire teaching of the body of literature called Upanishad is regarding this kind of knowledge which is communicated to a mind that is absolutely silent, absolutely quiet so that it discovers the ‘True-self’.
Having discovered the ‘True-Self’, one says, ‘Tat Tvam Asi’ meaning ‘you are none other than That–That which is the absolute ‘Supreme Reality’, Brahman, the ‘Truth’ or whatever you want to call it.