Introductory Remarks by Shankara
Though the name and the object signified by the name are one and the same, still the explanation1 has been given (here) by giving prominence2 to the name (Aum). Though in the Upaniṣadic passage,—“Aum, this word, is all this”—explanation has been furnished by giving prominence3 to the name (Aum), the same thought is again expounded by giving prominence to the thing signified by the name. The object is to realize the knowledge of the oneness of the name and the thing signified by it. Otherwise, (the explanation) that the knowledge of the thing is dependent on the name, might suggest that the oneness of the name and the thing is to be taken only in a figurative4 sense. The purpose of the knowledge of the unity (of the name and the thing signified by it) is to simultaneously remove, by a single effort, (the illusion of) both the name and the thing and establish (the nature of) Brahman which5 is other than both. Therefore,the Śruti says,’ “The quarters (Pādas) are the letters of Aum (Mātrā) and the letters are the quarters.”
Anandagiri Tika (glossary)
1 Explanation—i.e., of what is intended to be taught by the Upaniṣadic text.
2 Prominence—Because Aum is the first word of the first Upaniṣad. The purport of the sentence is that Aum is the symbol, the most universal, for all the phenomena of the world. Therefore prominence is given to Aum (abhidhāna).
3 Prominence—The second Upaniṣad is “All this is, truly, Brahman.” Hence the emphasis is on ‘All this’—which is the object (abhidheya) signified by Aum.
4 Figurative—i.e., the mere convention of calling a thing by a particular name.
5 Which is, etc.—The knowledge of the attributeless Brahman is possible only when the illusion of both the name and the thing signified by it is removed.
Therefore it says:—
Mandukya Upanishad, second verse:
सर्वं ह्येतद् ब्रह्मायमात्मा ब्रह्म सोऽयमात्मा चतुष्पात् ॥ २ ॥
sarvaṃ hyetad brahmāyamātmā brahma so ‘yamātmā catuṣpāt || 2 ||
2. All this is verily Brahman. This Ātman is Brahman. This Ātman has four quarters.
Shankara Bhashya (commentary)
All this is verily Brahman. All that has been said to consist merely of Aum (in the previous text) is Brahman. That Brahman which has been described1 (as existing) inferentially2 is now pointed out, as being directly3 known, by the passage, “This Self is Brahman”. The word this, meaning that which appears divided into four quarters,4 is pointed out as the innermost Self, with a gesture5 (of hand) by the passage, “This is Ātman”. That Ātman indicated by Aum, signifying both the higher and the lower Brahman, has6 four quarters (Pādas), not indeed, like the four feet (Pādas) of a cow,7 but like the four quarters (Pādas) of a coin8 known as Kārṣāpaṇa. The knowledge of the fourth (Turīya) is attained by merging the (previous) three, such as Viśva, etc., in it in9 the order of the previous one, in the succeeding one. Here10 the word ‘Pāda’ or ‘foot’ is used in11 the sense of instrument. The word ‘Pāda’ is again used in the sense of an object when the object to be achieved is the fourth (Turīya).
Anandagiri Tika (glossary)
1 Described—i.e., by the Śruti.
2 Inferentially—i.e., we cannot directly perceive its presence but we can infer it. It is opposed to aparokṣajñāna which refers to the knowledge of a thing that is not directly perceived but about the existence of which one becomes absolutely certain by means of what is known as realization.
3 Directly—The word pratyakṣa, nowadays, is applied, especially in the Nyāya Philosophy, to the knowledge of the objects of sense-perception. But occasionally it is used, in the Upaniṣad and the Vedāntic text, in the sense of aparokṣa.
4 Four quarters—Namely, Viśva (the waking state), Taijasa (dream state), Prājña (Suṣupti or the state of dreamless sleep) and Turīya which is same as Brahman or Ātman. These four quarters correspond to the three Mātrās of Aum and the Amātra of Aum. A, U and M are the three Mātrās. The fourth, which is known as Amātra or without a letter, has no corresponding letter or sound. This is silence or Ātman corresponding to Turīya. The idea of sound suggests the idea of soundlessness or silence from which sound may be said to proceed.
5 Gesture—i.e., by placing the hand on the region of the heart which, in popular belief, is the seat of Ātman.
6 Has, etc.— The four quarters are imagined in Ātman to facilitate the understanding of the pupil.
7 Cow—Because cow has actually four feet which are unrelated with one another.
8 Coin—Kārṣāpaṇa is a coin made up of four quarters. A quarter- Kārṣāpaṇa is merged in the half-Kārṣāpaṇa; the half is merged in the three -fourth- Kārṣāpaṇa and the three-quarters ultimately is merged in the full Kārṣāpaṇa.
9 In they etc.—Viśva is merged in Taijasa, Taijasa in Prājña and finally Prājña is merged in Turīya.
10 Here—It is because the ‘fourth’ pāda is realized by means of merging the three states in it.
11 In the sense of— It is because the attention is here drawn to the fourth ‘pāda’ which is the object of the enquiry.