The Upaniṣads contain the highest flights of Hindu philosophical thought. Since they are not the works of a single author and do not appear to propound a single system of philosophical thought, Bādarāyaṇa-Vyāsa undertook to streamline and systematize their thoughts through his well-known work called Brahmasūtras. (See BRAHMASŪTRAS for details.) This work, being in the form of aphorisms, could not be easily comprehended without the aid of a suitable commentary. Since it commanded a great respect in the Hindu philosophical tradition, several ācāryas (spiritual and reli-gious preceptors) owing allegiance to different thought systems, wrote expositions on it, attempting to show that it expounds their system of philosophy. Among such ācāryas, Śaṅkara, Rāmānuja and Madhva have been considered the chief ones.
Madhvācārya (A. D. 1238-1317) the chief exponent of the Dvaita Vedānta (dualistic Vedānta) is reputed to have written four works on the Brahmasūtras: the Brahmasūtrabhāṣya, Anuvyākhyāna, Nyāyavivaraṇa and Aṇubhāṣya.
The Aṇubhāṣya, as the very name indicates, is a very small (aṇu = tiny) metrical work comprising 32 ślokas (verses) in the simple anuṣṭubh metre, divided into four chapters of 8 ślokas each. This is said to have been composed by Madhva for the convenience of his disciples who were in the habit of reading the entire bhāṣya on the Brahmasūtras before taking their food.
The first chapter expounds the greatness of Lord Viṣṇu, who is the source of all beings and things. The second chapter brings out the untenability of interpretations of the Upaniṣaḍic passages by other schools like the Sāṅkhya. The third chapter extols jñāna (knowledge of God) and advises the aspirants to eschew evil deeds and perform only good deeds. An important doctrine that is set forth here is that there is gradation even in mukti (liberation). The last chapter describes ways of attaining mukti.
Aṇubhāṣya is also known as Sarva-śāstrārtha-saṅgraha and has several commentaries by Jayatīrtha, Ananta Bhaṭṭa, Rāghavendra Tīrtha and others.
Vallabhācārya (A. D. 1481—1533) another of the well-known ācāryas of the pluralistic schools, has written a commentary on the Brahmasūtras called Aṇubhāṣya which, again, has a few sub-commentaries.