Kaṭha Upaniṣad · 2.3.12
नैव वाचा न मनसा प्राप्तुं शक्यो न चक्शुषा । अस्तीति ब्रुवतोऽन्यत्र कथं तदुपलभ्यते ॥ १२ ॥
naiva vācā na manasā prāptuṃ śakyo na cakśuṣā | astīti bruvato'nyatra kathaṃ tadupalabhyate || 12 ||
Neither by speech, nor by the mind, nor by the eye can It be attained. How can It be obtained by one other than he who says ‘It Is’?
The Ātman transcends all ordinary means of knowledge. Vāc (speech) can describe objects, not the subject. Manas (mind) can think about things, not its own foundation. Cakṣuṣā (the eye) can see forms, not the light that makes them visible.
The rhetorical question points to the fact that only one who affirms “asti” (is, exists), only one who has faith in the existence of the Real, can begin the journey toward upalabdhi (obtainment, realization). The skeptic who denies the transcendent cannot realize it, because they have closed the door before attempting to open it.
For the yogi, this means that śraddhā (faith, trust) is the prerequisite. Not blind faith in dogmas, but confidence that there is something beyond what the senses and mind can grasp. With that confidence, we sit to meditate, knowing that silence is more eloquent than any word.