Through the ages, many viewpoints have emerged on matters relating to Vedanta as different people have tried to understand in their individual ways. This esoteric knowledge transcends the theoretical, physical and material planes and is realised at the inner level. So if someone professes to have the knowledge of Brahman, how is one to know that what is understood is the ultimate truth? The Upanishads reiterate that despite the difficulties in this uphill task, instruction on the Atma Tatva has taken place when both preceptor and pupil rise up to the expected levels, pointed out Sri Mani Dravid Sastrigal in a lecture.
Of course, failure to transmit the knowledge can happen owing to various reasons, as when either the instructor is not realised or if the student is not fully in earnest.
The Katopanishad features a situation in which the young boy Nachiketas seeks instruction on these matters from Yama. “When a man dies, some say the Self, which is distinct from the body, senses, mind and intellect, and which connected to a fresh body in the next life, exists. Others say a Self of this kind does not exist. It is a thing whose knowledge cannot be acquired through direct perception; nor can we gain it through inference. Yet, a clear knowledge of this is believed to be the supreme goal for human beings. I would like to be instructed by you in this regard.” Yama now wishes to test whether the boy is fit to imbibe this subtle knowledge. He tells Nachiketas that even the gods have entertained doubts with regard to this since days of yore. So, he would rather that the boy asked for some other boon instead of seeking this instruction. The boy says: “Since you yourself say that even the gods have doubts about this knowledge which is difficult to gain, I am convinced that no instructor other than you can enlighten me. There is no other boon comparable to this one.”
Here both preceptor and pupil fulfil the eligibility standards. It is believed that a Jivatma who gives up his life in Kasi is privileged to be instructed in the Pranava by Siva Himself. Likewise, Krishna’s teaching is considered authoritative and the sincere seeker stands to gain from it as did Arjuna.