BG Chap 13 - The fallacy of "one knower"
The argument is rejected, because of the impossibility of teaching anything in this way. If the Lord is in ignorance how can He teach? If he is beyond the duality of seeing self and other objects, then He has no other object to whom He can teach. If what the impersonalists claim is true, Kṛṣṇa would be contradicting His own statements in Chapter Fifteen wherein He clearly makes distinctions between the soul and the Supersoul. If the soul and the Supersoul are factually one, as Māyāvādīs claim, how could one aspect of the “one,” which is by definition undifferentiated, give knowledge to the other aspect of the “one”? How could the other aspect be lacking? How could something undifferentiated even possess an aspect? If both were “one,” absolutely no differentiation (even in terms of knowing and not knowing) could exist. If one aspect gets liberated, then all other aspects should also be liberated.
The problem stems basically from trying to read one's own philosophy into Kṛṣṇa's words, instead of accepting straight what Kṛṣṇa says. He says kṣetra-jñaṁ cāpi māṁ viddhi sarva-ksetra. A straight forward reading will be: And I am also a knower in all fields. He does not say that the jiva is a knower in all fields when He talks about the knower in the previous verse. And He does not identify Himself as the knower mentioned in the previous verse, which was a speculation by the Mayavadis.