Udayana

Udayana, (Devanagari: उदयन) also known as Udayanācārya (Udyanacharya, or Master Udayana), (circa 975 - 1050 CE) was an Indian philosopher and logician of the tenth century of the Nyaya school who attempted to devise a rational theology to prove the existence of God using logic and counter the attack on the existence of God at the hands of Buddhist philosophers such as Dharmakīrti, Jñānaśrī and against the Indian school of materialism (Chārvaka). He is considered to be the most important philosopher of the Nyāya tradition.

He worked to reconcile the views held by the two major schools of logic (Nyaya and Vaisheshika). This became the root of the Navya-Nyāya ("New Nyāya") school of the thirteenth century, established by the Gangesha Upadhyaya school of "right" reasoning, which is still recognized and followed in some regions of India today. He lived in Kariyan village in Mithila, near present-day Darbhanga, Bihar state, India.

Udayana wrote a sub-gloss on Vachaspati Misra's work called the Nyaya-vaartika-taatparya-tiikaa-parishuddhi. He wrote several other works such as the Kusumanjali, Atma-tattva-viveka, Kiranaavali and Nyaya-parishishhta (also called Bodha siddhi or Bodha shuddhi).

He is given credit by Naiyāyikas for having demolished in a final fashion the claims of the Buddhist logicians. All his known works are thought to have been preserved, attesting to the importance given to him in Indian philosophy.

It is accepted by most scholars now that he was from Mithila, Bihar. In the Nyāya-Vaiśeṣika school itself, to which he belongs, he occupies a singular position of authority and renown. Flourishing at the period of transition from the Older Nyāya to the New (Navya-Nyāya), he shines as an unrivalled master of the former and an inspiring herald of the latter. For example, Gaṇgeśa Upādhyāya, the 14th century Indian philosopher and mathematician who established the Navya-Nyāya school refers to Udayana as "Acāryaḥ" (lit. Master/Teacher). D. C. Bhattacharya observes: "From the 12th century onwards he [= Udayana] was looked upon as the greatest exponent of the Nyāya-Vaiśeṣika doctrines and was the greatest target of all scholars of the opposing camps".

One Indian writer of the 14th century, Mādhavacharya, the author of the Sarvadarsanasamgraha, speaks of him not only as "one whose fame had spread everywhere" (viśvavikhyātakīrtih), but also as "one who has seen the opposite shore of the ocean of the principles of logic" (nyāyanayapārāvārapāradṛk), an epithet which shows his fame as a logician.

The controversy about Udayana's lifetime seemed to have been settled by the discovery of the Lakṣaṇāvalī, the concluding verse of which states that it was written in Saka era 906 (984—985 CE). Hence, he was active as a philosopher from the late 10th century to the beginning of the 11th century.

Udayana's work represents a synthesis of ontological and epistemological theories, combining the Vaisheshika system of categories (padarthas) with the Nyaya doctrine of pramanas (means of knowledge).