“Although we say that the pramana is Vedanta, it is really a thought, a vrtti, that is the pramana. Pramana is that which gives rise to knowledge.
The mind, being the place where the vrtti occurs, is called antah-karana, meaning, inner instrument. When you are exposed to a teacher or a teaching, your buddhi, the intellect, assumes the very form of the pramana, the teaching. Therefore, the guru’s buddhi or the teaching, and your buddhi become one and the same.
The guru’s buddhi tells us, ‘You are that, tat-tvam-asi.’ Here, the guru-buddhi is turned toward Arjuna, who represents the confused anta-karana, the ego, or one’s notion of I…. Exposed to the teaching, one’s own buddhi assumes the very meaning of the teaching and thereby becomes a guru to oneself.
If your buddhi does not know this fact, tat tvam asi, it cannot tell you. It cannot tell you anything more than what it knows. This is why continually asking, ‘Who am I?’ does not work. Nothing can happen because you do not know what you do not know. Someone has to teach you. You cannot simply ask, ‘Who am I’, and expect to get an answer, because the ‘I’ that is always present is the one asking the question. How will the answer to such a question come? You cannot hope to stumble upon the fact. The fact is you; therefore, you are not going to stumble upon an answer that is anything more than what you already know.”
~ Swami Dayananda, Bhagavad Gita, Home Study Course