Nyaya Ratnakara is a mimamsa text which is a commentary on Kumarila Bhatta. The celebrated author of Nyaya Ratnakara is Parthasarathi Mishra; the other well-known works of the author are – Sastradipika, Tantraratna (commentary on Tuptika),and Nyayaratnamala, an independent work (with the commentary Nyayaratna of Ramanujacharya.
There is no unanimity of opinion on the date of the Parthasarathi Mishra. He came after Mandana Mishra, who was a contemporary of Adi Shankaracharya. P.V. Kane in his History of Dharmasastra (V. 2. P. 1199), puts him in 900 – 1100 CE. It will not be wrong to place Parthasarathi Mishra in the latter part of the 9th century CE or in the earlier part of the 10th century CE. He was one of the most celebrated adherents of Kumarila Bhatta. According to him, Vedas are to be regarded as eternal and self-validating. The doctrine of self-validity of knowledge is the cornerstone of the Mimamsa system.
The Bhatta School speaks of six legitimate ways of knowing (pramanas), pratyaksha (perception), anumana (inference), sabda or aptavacana (verbal testimony), upamana (comparison), arthapatti (presumption), and anupalabadhi or abhava (non-apprehension).
The Prabhakara School does not accept abhava as one of the pramanas. According to Parthasarathi Mishra, the valid apprehension is that which is free from discrepancies, apprehending thins not previously apprehended (Sastradipika). According to Sutra (4.1.188), followed by Sabara,Prabhakara, and Kumarila, actions may be undertaken either for the sake of the agent (purushartha) or for the sake of the offering (kratvartha), while Parthasarathi adds a third class of those which are not for the purpose, giving as an instance the Agnyadhana, the piling of the sacred fire.