Some (commentators)[121] quote under the present Sutra the following passages, 'the pra/n/a of pra/n/a' (B/ri/. Up. IV, 4, 18), and 'for to pra/n/a mind is fastened' (Ch. Up. VI, 8, 2). But that is wrong since these two passages offer no opportunity for any discussion, the former on account of the separation of the words, the latter on account of the general topic. When we meet with a phrase such as 'the father of the father' we understand at once that the genitive denotes a father different from the father denoted by the nominative. Analogously we infer from the separation of words contained in the phrase, 'the breath of breath,' that the 'breath of breath' is different from the ordinary breath (denoted by the genitive 'of breath'). For one and the same thing cannot, by means of a genitive, be predicated of--and thus distinguished from--itself. Concerning the second passage we remark that, if the matter constituting the general topic of some chapter is referred to in that chapter under a different name, we yet conclude, from the general topic, that that special matter is meant. For instance, when we meet in the section which treats of the jyotish/t/oma sacrifice with the passage, 'in every spring he is to offer the jyotis sacrifice,' we at once understand that the word denotes the jyotish/t/oma. If we therefore meet with the clause 'to pra/n/a mind is fastened' in a section of which the highest Brahman is the topic, we do not for a moment suppose that the word pra/n/a should there denote the ordinary breath which is a mere modification of air. The two passages thus do not offer any matter for discussion, and hence do not furnish appropriate instances for the Sutra. We have shown, on the other hand, that the passage about the pra/n/a, which is the deity of the prastava, allows room for doubt, purvapaksha and final decision. 24. The 'light' (is Brahman), on account of the mention of feet (in a passage which is connected with the passage about the light). Scripture says (Ch. Up. III, 13, 7), 'Now that light which shines above this heaven, higher than all, higher than everything, in the highest worlds beyond which there are no other worlds that is the same light which is within man.' Here the doubt presents itself whether the word 'light' denotes the light of the sun and the like, or the highest Self. Under the preceding Sutras we had shown that some words which ordinarily have different meanings yet in certain passages denote Brahman, since characteristic marks of the latter are mentioned. Here the question has to be discussed whether, in connexion with the passage quoted, characteristic marks of Brahman are mentioned or not.