Sri Aurobindo translates Mundaka Upanishad, Chapter 3, Section 2, Verse 3: “This Self is not won by exegesis, nor by brain-power, nor by much learning of Scripture. Only by him whom It chooses can it be won; to him this Self unveils its own body.”
In today’s world we put a high premium on “brain power”, mental development and learning. The analytical powers are highly valued. The brilliance of a strong mental capacity is recognized and appreciated. Our entire technological society is founded in an ever-greater focus on developing the mind. Yet the knowledge provided by the mind is at all times a secondary form of knowledge, based in the perceptions of the senses and the nervous impulses being sent to the brain. Study and analysis provide exercise for this mental development, but they remain a secondary form of knowledge, not knowledge by direct experience. We are reminded that one can read all the books in the world that talk about swimming, but until we actually get in the water and do it, we truly do not know how to swim.
Similarly, the spiritual knowledge of Oneness is not achieved through any feats of the intellect. On the contrary, strong mental development may actually prevent the individual from the realisation by focusing the attention on these secondary means. Mental pride and arrogance also may cloud the mind and prevent new insights from being understood and accepted.
A number of Upanishads make it clear that neither mind nor speech can attain to the truth of the Spirit. This realisation requires a different type of knowledge, a shifting of the standpoint from the egoistic to the divine. This brings about knowledge by direct experience, knowledge by identity. Thus the Mundaka Upanishad notes that the Self must choose to reveal itself to the seeker. This shift of standpoint means that the seeker identifies with the Self and thus, can see, experience and know based on the viewpoint of the Self. The shift is not accomplished by individual effort. The being is prepared to receive through the practices of quieting the mind stuff and the quelling of the desires that disturb the being. This is where individual effort ends as the being approaches the point in consciousness that transitions from the ego to the Self. The truth of Oneness, the Existence-Consciousness-Bliss (Sat-Chit-Ananda) of the Supreme can then manifest itself through a being now ready and receptive to this new direct form of awareness.
Sri Aurobindo, The Upanishads, Mundaka Upanishad, pp. 193-210