His father said to him: 'Svetaketu, as you are so conceited, considering yourself so well-read, and so stern, my dear, have you ever asked for that instruction by which we hear what cannot be heard, by which we perceive what cannot be perceived, by which we know what cannot be known?'

In plain words: His father gently asks him: since you are so proud of your learning, did you ever ask about the one teaching that lets you hear what cannot be heard, see what cannot be seen, and know what cannot be known?