Kena Upanishad — Not Known by the Known
The Kena Upanishad's repeated declaration that Brahman is 'not what the eye sees, not what the mind thinks' — yet is the very power by which seeing and thinking occur — is the most precise Upanishadic analysis of Brahman's nature.
The Kena Upanishad opens with the most penetrating series of questions in Vedantic literature: 'By whose will directed does the mind proceed to its object? At whose command does the first breath go forth? At whose will do we utter this speech? What god directs the eye, or the ear?' The answers follow the apophatic pattern: 'It is not thought by the mind — but by which the mind, they say, is thought. Know that alone as Brahman, not this which people worship here.' Brahman is not an object that can be seen, thought, or known — but is the very power (the 'eye of the eye,' the 'mind of the mind') by which seeing, thinking, and knowing occur. The paradox: Brahman is the most intimately known reality (it is what makes knowing possible) yet cannot be known as an object of knowledge. The famous exchange with Indra — where the yaksha (Brahman in disguise) appears before the devas and they cannot identify it — dramatizes the teaching: Brahman is always present but never directly seen, always the seer and never the seen.
That which is not thought by the mind, but by which the mind is thought — that alone is Brahman, not what people worship here.
Philosopher Thomas Nagel's 'What Is It Like to Be a Bat?' — arguing that subjective consciousness cannot be captured in any objective third-person description — makes the same point as the Kena Upanishad: the knowing capacity itself cannot be known as an object, because it is always the knowing rather than the known.
Kena Upanishad