Sutra 2.3.22

22. If it be said that (the soul) is not atomic, on account of scriptural statement of (what is) not that; we say no, on account of the other one being the topic.

The passage 'He who is within the heart, surrounded by the Prāṇas, the person consisting of knowledge' (Bṛ. Up. IV, 3, 7) introduces as the topic of discussion the personal Self, and further on in the same chapter we read 'the unborn Self, the great one' (IV, 4, 22). The personal Self, being expressly called great, cannot, therefore, be atomic!—Not so, we reply. 'Since the other one is the topic.' In the second text quoted that Self which is other than the personal Self—i.e. the highest Self (prājña) constitutes the topic. In the beginning of the chapter, indeed, the individual Self is introduced, but later on, between the two texts quoted, the instruction begins to concern itself with the highest Self, 'he by whom there is known the Self of intelligence' (pratibuddha ātmā; IV, 4, 13). It is this latter Self which, in 22 is called great, not the individual Self.