Sri Aurobindo translates Katha Upanishad, First Chapter, Second Cycle, Verses 23-25: “The Self is not to be won by eloquent teaching, nor by brain power, nor by much learning: but only he whom this Being chooses can win Him; for to him this Self bares His body. None who has not ceased from doing evil, or who is not calm, or not concentrated in his being, or whose mind has not been tranquillised, can by wisdom attain to Him. He to whom the sages are as meat and heroes as food for his eating and Death is an ingredient of His banquet, how thus shall one know of Him where He abides?”
It is important to recognize that instead of simply answer Nachiketas’ request for his third boon, Yama has engaged in a lengthy discussion of the process of knowing, and the methodology required to know Brahman, which differs from the process of sense perception and analysis used by the mind to understand the manifested world around us. The Upanishad makes clear that the usual tools and processes of knowledge we use in examining and responding to the outer world are not going to succeed in knowing Brahman; yet it also makes clear that knowing Brahman is indeed possible. This implies a different type of knowing, a knowledge by identity rather than an intellectual understanding or marshaling of details and facts in an organized format suitable for the application of logic and reason. It is also implied, therefore, that the answer to the third boon requires a different type of knowing and preparation by the seeker. It is not going to be a mental understanding.
The Upanishad also makes clear that the Brahman is not to be won by human effort. When the psyche becomes tranquil, focused and receptive, a shift that brings about an identity with the Brahman can occur. A desire-filled vital being, a clamoring physical body, or an ambitious mind creates too many “waves” in the “mind-stuff” (chitta), so that there is no chance of a clear reflection. These create interference in the ability of the being to shift to a different standpoint. Many commentators try to make this into a moral commentary about not doing evil, but the intention is not so much one of following a specific set of moral rules (which vary from culture to culture) as in eliminating movements that “stir up” the mind-stuff and create turbulence in the being. The sages recognized that the action of desire is disruptive, so that the path of true knowledge lies in preparing the entire being to receive and reflect without the perturbations caused through interference by the promptings of body, life and mind.
Sri Aurobindo, The Upanishads, Katha Upanishad, pp. 213-241, and Kapali Sastry, Lights on the Upanishads, pp. 104-129