Among all the Indian Philosophical systems, the Advaita Vedānta of Śaṅkara and his followers can boast of the maximum number of written works. One of the writers in this line who has done yeomen service by writing sub-commentaries on all the major works of Śaṅkara is Ānanda-jñāna, celebrated as Ānandagiri, who lived in the 14th cent. A. D. Known as Janārdana in his premonastic life, he was the son of one Sūryanārāyaṇa and belonged to the country called Cera (now in Tamil Nadu). He was probably a devotee of Viṣṇu. His guru was Śuddhānanda. His ṭīkā (comment) on the Bṛhadāraṇyaka Vārttika of Sureśvara (7th—8th cent. A.D.) has been highly appreciated. In his original polemical work Vedānta-tarka-saṅgraha he has refuted the Vaiśeṣika categories like dravya, guṇa etc. In his conclusions he has tried to follow his predecessors like Ānandabodha (11th cent. A. D.) and others. He holds that avidyā or ajñāna which is an indeterminable false entity is the stuff of this world. Ajñāna is one only and is supported by Brahman.