29. But (the Self) is designated as that because it has that quality (viz. knowledge) for its essential quality; as in the case of the intelligent (prâgña) Self.
The 'but' discards the objection. Because that quality, viz. the quality of knowledge, is the essential quality, therefore the Self is, in the passages quoted, designated as knowledge. For knowledge constitutes the essential quality of the Self. Similarly, the intelligent highest Self is occasionally called 'Bliss,' because bliss is its essential quality. Compare 'If that bliss existed not in the ether' (Taitt. Up. II, 7, 1); 'He perceived that bliss is Brahman' (Taitt. Up. III, 6, 1). That bliss is the essential attribute of Brahman is proved by texts such as 'That is one bliss of Brahman'; 'He who knows the bliss of Brahman is afraid of nothing' (Taitt. Up. II, 4, 1).--Or else the analogous case to which the Sûtra refers may be that of the intelligent Brahman being designated by the term 'knowledge,' in texts such as 'Truth, knowledge, the Infinite is Brahman' (Taitt. Up. II, 1). That knowledge is the essential quality of Brahman is known from passages such as 'together with the intelligent Brahman' (Taitt. Up. II, 1, 1); 'He who is all-knowing' (Mu. Up. I, 1, 9).