The rishi asks, “How do I express this to you? How do I get this through to you in a manner that you understand? I am myself confused as to how to teach this to you.”
So, you see, even in those days, the teacher had to face the difficulty of expressing the subtle truths of the Upanishads. According to the rishi, even if one has understood it, one does not know how to express it—the reason being that we are talking about a reality that is of a totally different dimension.
We are normally accustomed to thinking in three-dimensional forms—length, breadth, and height—and cannot conceive of forms having a fourth dimension or a fifth dimension. Such dimensions may exist, but we know nothing about them.
Even if conceived, it is difficult to express it in three-dimensional language. People who are into higher mathematics or quantum physics will appreciate what is being said here. So, the rishi says, “The mind also cannot reach there and, therefore, I find it difficult to teach it. I don’t know how to teach this to you.” Is the rishi trying to take us for a ride? If it cannot be understood or explained by anything if the mind itself cannot reach it, what’s the use of the Upanishads? What are we going to do?