Then Maitreyi said: 'Here thou hast bewildered me, Sir, when thou sayest that having departed, there is no more knowledge.' But Yagnavalkya replied: 'O Maitreyi, I say nothing that is bewildering. This is enough, O beloved, for wisdom. 'For when there is as it were duality, then one sees the other, one smells the other, one hears the other, one salutes the other, one perceives the other, one knows the other; but when the Self only is all this, how should he smell another, how should he see another, how should he hear another, how should he salute another, how should he perceive another, how should he know another? How should he know Him by whom he knows all this? How, O beloved, should he know (himself), the Knower?'

In plain words: Maitreyi says she is confused by the idea that no awareness remains after death. Yajnavalkya explains. When there seem to be two, one sees, hears and knows the other. But when everything is the one Self, there is no 'other' left to see or know. And the Knower itself cannot be known like an object.