It is difficult to ascertain definitely the date of the _Vais'e@sika sutras_ by Ka@nada, also called Aulukya the son of Uluka, though there is every reason to suppose it to be pre-Buddhistic. Itappears from the _Vayu purana_ that he was born in Prabhasa near Dvaraka, and was the disciple of Somas'arma. The time of Pras'astapada who wrote a bha@sya (commentary) of the _Vais'e@sika sutras_ cannot also unfortunately be ascertained. The peculiarity of Pras'astapada's bha@sya is this that unlike other bha@syas (which first give brief explanations of the text of the sutras and then continue to elaborate independent explanations by explaining the first brief comments), it does not follow the sutras but is an independent dissertation based on their main contents [Footnote ref 455]. There were two other bha@syas on the _Vais'e@sika sutras_, namely _Rava@na-bha@sya_ and _Bharadvaja-v@rtti_, but these are now probably lost. References to the former are found in _Kira@navalibhaskara_ of Padmanabha Mis'ra and also in _Ratnaprabha_ 2. 2. II. Four commentaries were written on this bha@sya, namely _Vyomavati_ by Vyomas'ekharacarya, _Nyayakandali_ by S'ridhara, _Kira@navali_ by Udayana (984 A.D.) and _Lilavati_ S'rivatsacarya. In addition to these Jagadis'a Bha@t@tacarya of Navadvipa and S'a@nkara Mis'ra wrote two other commentaries on the _Pras'astapada-bhasya_, namely _Bhasyasukti_ and _Ka@nada-rahasya_. S'a@nkara Mis'ra (1425 A.D.) also wrote a commentary on the _Vais'e@sika sutras_ called the _Upaskara_. Of these _Nyaya-kandali_ of S'ridhara on account of its simplicity of style and elaborate nature of exposition is probably the best for a modern student of Vais'e@sika. Its author was a native of the village of Bhuris@r@s@ti in Bengal (Ra@dha). His father's name was Baladeva and mother's name was Acchoka and he wrote his work in 913 S'aka era (990 A.D.) as he himself writes at the end of his work.
The _Nyaya sutra_ was written by Ak@sapada or Gautama, and the earliest commentary on it written by Vatsyayana is known as the _Vatsyayana-bha@sya_. The date of Vatsyayana has notbeen definitely settled, but there is reason to believe that he lived some time in the beginning of the fourth century A.D. Jacobi places him in 300 A.D. Udyotakara (about 635 A.D.) wrote a _Varttika_ on Vatsyayana's bha@sya to establish the Nyaya views and to refute the criticisms of the Buddhist logician Di@nnaga (about 500 A.D.) in his _Prama@nasamuccaya_. Vacaspatimis'ra (840 A.D.) wrote a sub-commentary on the _Nyayavarttika_ of Udyotakara called _Nyayavarttikatatparya@tika_ in order to make clear the right meanings of Udyotakara's _Varttika_ which was sinking in the mud as it were through numerous other bad writings (_dustarakunibandhapa@nkamagnanam_). Udayana (984 A.D.) wrote a sub-commentary on the _Tatparya@tika_ called _Tatparya@tikaparis'uddhi_. Varddhamana (1225 A.D.) wrote a sub-commentary on that called the _Nyayanibandhaprakas'a_. Padmanabha wrote a sub-commentary on that called _Varddhamanendu_ and S'a@nkara Mis'ra (1425 A.D.) wrote a sub-commentary on that called the _Nyayatatparyama@n@dana_. In the seventeenth century Vis'vanatha wrote an independent short commentary known as _Vis'vanathav@rtti_, on the _Nyaya sutra_, and Radhamohana wrote a separate commentary on the _Nyaya sutras_ known as _Nyayasutravivara@na_. In addition to these works on the _Nyaya sutras_ many other independent works of great philosophical value have been written on the Nyaya system. The most important of these in medieval times is the _Nyayamanjari_ of Jayanta (880 A.D.), who flourished shortly after Vacaspatimis'ra. Jayanta chooses some of the _Nyaya sutras_ for interpretation, but he discusses the Nyaya views quite independently, and criticizes the views of other systems of Indian thought of his time. It is far more comprehensive than Vacaspati's _Tatparya@tika_, and its style is most delightfully lucid. Another important work is Udayana's _Kusumanjali_ in which he tries to prove the existence of Is'vara (God). This work ought to be read with its commentary _Prakas'a_ by Varddhamana (1225 A.D.) and its sub-commentary _Makaranda_ by Rucidatta (1275 A.D.). Udayana's _Atmatattvaviveka_ is a polemical work against the Buddhists, in which he tries to establish the Nyaya doctrine of soul. In addition to these we have a number of useful works on Nyaya in later times. Of these the following deserve special mention in connection with the present work. _Bha@sapariccheda_ by Vis'vanatha with its commentaries _Muktavali, Dinakari_ and _Ramarudri, Tarkasamgraha_ with _Nyayanir@naya, Tarkabka@sa_ of Kes'ava Mis'ra with the commentary _Nyayapradipa, Saptapadarthi_ of S'ivaditya, _Tarkikarak@sa_ of Varadaraja with the commentary _Ni@ska@n@taka_ of Mallinatha, _Nyayasara_ of Madhava Deva of the city of Dhara and _Nyayasiddhantamanjari_ of Janakinatha Bha@t@tacarya with the _Nyayamanjarisara_ by Yadavacarya, and _Nyayasiddhantadipa_ of S'a@sadhara with _Prabha_ by S'e@sanantacarya.
The new school of Nyaya philosophy known as Navya-Nyaya began with Ga@nges'a Upadhyaya of Mithila, about 1200 A.D. Ga@nges'a wrote only on the four prama@nas admitted by the Nyaya, viz. pratyak@sa, anumana, upamana, and s'abda, and not on any of the topics of Nyaya metaphysics. But it so happened that his discussions on anumana (inference) attracted unusually great attention in Navadvipa (Bengal), and large numbers of commentaries and commentaries of commentaries were written on the anumana portion of his work _Tattvacintama@ni, and many independent treatises on sabda and anumana were also written by the scholars of Bengal, which became thenceforth for some centuries the home of Nyaya studies. The commentaries of Raghunatha S'iroma@ni (1500 A.D.), Mathura Bha@t@tacarya (1580 A.D.), Gadadhara Bha@t@tacarya (1650 A.D.) and Jagadisa Bha@t@tacarya (1590 A.D.), commentaries on S'iroma@ni's commentary on _Tattvacintamani, had been very widely read in Bengal. The new school of Nyaya became the most important study in Navadvipa and there appeared a series of thinkers who produced an extensive literature on the subject [Footnote ref 456].
The contribution was not in the direction of metaphysics, theology, ethics, or religion, but consisted mainly in developing a system of linguistic notations to specify accurately and precisely any concept or its relation with other concepts [Footnote ref 457]. Thus for example when they wished to define precisely the nature of the concomitance of one concept with another (e.g. smoke and fire), they would so specify the relation that the exact nature of the concomitance should be clearly expressed, and that there should be no confusion or ambiguity. Close subtle analytic thinking and the development of a system of highly technicalexpressions mark the development of this literature. The technical expressions invented by this school were thus generally accepted even by other systems of thought, wherever the need of accurate and subtle thinking was felt. But from the time that Sanskrit ceased to be the vehicle of philosophical thinking in India the importance of this literature has gradually lost ground, and it can hardly be hoped that it will ever regain its old position by attracting enthusiastic students in large numbers.
I cannot close this chapter without mentioning the fact that so far as the logical portion of the Nyaya system is concerned, though Ak@sapada was the first to write a comprehensive account of it, the Jains and Buddhists in medieval times had independently worked at this subject and had criticized the Nyaya account of logic and made valuable contributions. In Jaina logic _Das'avaikalikaniryukti_ of Bhadrabahu (357 B.C.), Umasvati's _Tattvarthadhigama sutra_, _Nyayavatara_ of Siddhasena Divakara (533 A.D.) Ma@nikya Nandi's (800 A.D.) _Parik@samukha sutra_, and _Prama@nanayatattvalokala@mkara_ of Deva Suri (1159 A.D.) and _Prameyakamalamarta@n@da_ of Prabhacandra deserve special notice. _Prama@nasamuccaya_ and _Nyayapraves'a_ of Di@nnaga (500 A.D.), _Prama@nayarttika karika_ and _Nyayabindu_ of Dharmakirtti (650 A.D.) with the commentary of Dharmottara are the most interesting of the Buddhist works on systematic logic [Footnote ref 458]. The diverse points of difference between the Hindu, Jain and Buddhist logic require to be dealt with in a separate work on Indian logic and can hardly be treated within the compass of the present volume.
It is interesting to notice that between the _Vatsyayana bha@sya_ and the Udyotakara's _Varttika_ no Hindu work on logic of importance seems to have been written: it appears that the science of logic in this period was in the hands of the Jains and the Buddhists; and it was Di@nnaga's criticism of Hindu Nyaya that roused Udyotakara to write the _Varttika_. The Buddhist and the Jain method of treating logic separately from metaphysics as an independent study was not accepted by the Hindus till we come to Ga@nges'a, and there is probably only one Hindu work of importance on Nyaya in the Buddhist style namely _Nyayasara_ of Bhasarvajna. Other older Hindu works generally treated ofinference only along with metaphysical and other points of Nyaya interest [Footnote ref 459].