Satis Chandra Vidyabhushana in his “A History of Indian Logic” states that India and Greece are the only countries in the whole world which perfected the art of logic and debate. Ultimately deriving from Gautama’s Anviksiki or the Science of Inquiry, India’s Tarka and Nyaya Sastra dealt extensively with the art of debate – how to conduct a debate, who should be the audience, how should the debaters conduct and what defines a victory. By around 1st Century AD, Inquiry as propounded by Gautama transmorphed into Logic and Philosophy, with many doyens – even Buddhist and Jain writing over it.

There is an extensive discussion on the topic of debate and an exhaustive list of twenty two defeats are listed by Gautama in his Nyaya Sutras. Looking at them, one would notice that they are still relevant even after they seeing the light of the day almost 2500 years ago.

pratijñāhāniḥ pratijñāntaraṃ pratijñāvirodhaḥ pratijñāsannyāso hetvantaram arthāntaraṃ nirarthakam avijñātārtham apārthakam aprāpta kālaṃ nyÅ«nam adhikaṃ punaruktam ananubhāṣaṇam ajñānam apratibhā viká¹£epo matānujñā paryanuyojyopeká¹£aṇaṃ niranuyojyānuyogo ‘pasiddhānto hetvā bhāsāśca nigrahasthānāni 5.2.1

The occasions for rebuke are the following : —

1. Hurting the proposition, 2. Shifting the proposition, 3. Opposing the proposition, 4. Renouncing the proposition, 5. Shifting the reason, 6. Shifting the topic, 7. The meaningless, 8. The unintelligible, 9. The incoherent, 10. The inopportune, 11. Saying too little, 12. Saying too much, 13. Repetition, 14. Silence, 15. Ignorance, 16. Non-ingenuity, 17. Evasion, 18. Admission of an opinion, 19. Overlooking the censurable, 20. Censuring the non-censurable, 21. Deviating from a tenet, and 22. The semblance of a reason.

A detailed reading of these tenets goes thus.

NameAphorismMeaning
Pratijna Hani
(Hurting the Proposition)
pratidṛṣṭāntadharmābhyanujñā svadṛṣṭānte pratijñāhāniḥOccurs when one admits in his own example, the character of a counter example
Pratijnaantara
(Shifting the Proposition)
 pratijñātārthapratiá¹£edhadharmavikalpāt tadarthanirdeśaḥ pratijñāntara.Arises when a proposition being opposed one defends it by importing a new character to one’s example and counter-example.
Pratijna Virodha
(Opposing the Proposition)
 pratijñāhetvorvirodhaḥ pratijñāvirodhaḥOccurs when the proposition and its reason are opposed, to each other.
Pratijna Sanyasa
(Renouncing the Proposition)
 paká¹£apratiá¹£edhe pratijñātārthāpanayanaṃ pratijñāsannyāsaḥA proposition being opposed if one disclaims its import
Hetvantara
(Shifting the Reason)
 aviśeá¹£okte hetau pratiá¹£iddhe viśeá¹£amicchato hetvantaramOccurs when the reason of a general character being opposed one attaches a special character to it. 
Arthantara
(Shifting the Topic)
 prakṛtādarthādapratisambddhārthamarthāntaramAn argument which setting aside the real topic introduces one which is irrelevant.
Nirarthaka
(The Meaningless)
 varṇakramanirdeśavannirarthakamAn argument which is based on a non-sensical combination of letters into a series
Avijnanartha
(The Unintelligible)
 pariá¹£atprativādibhyāṃ trirabhihitamapyavijñātamavijñātārthamAn argument, which although repeated three times, is understood neither by the audience nor by the opponent.
Apaarthaka
(The Incoherent)
 paurvāparyāyogādapratisambaddhārthamapārthakamAn argument which conveys no connected meaning on account of the words being strung together without any syntactical order
Apraptakala
(The Inopportune)
 avayavaviparyāsavacanamaprāptakālamAn argument the parts of which are mentioned without any order of precedence.
Nyunata
(Saying too little)
 hÄ«namanyatamenāpyavayavena nyÅ«namAn argument lacks even one of its parts
Adhika
(Saying too much)
 hetÅ«dāharaṇādhikam adhikamAn argument which consists of more than one reason or example.
Punarukta
(Repetition)
 Å›abdārthayoḥ punarvacanaṃ punaruktam anyatra anuvādāt
 anuvāde tu apunaruktaṃ śabdābhyāsāt arthaviśeá¹£opapatteḥ
 arthāt āpannasya svaśabdena punarvacanam
An argument in which (except in the case of reinculcation) the word or the meaning is said over again.
In reinculcation there is no repetition in as much as a special meaning is deduced from the word which is repeated.
Repetition consists also in mentioning a thing by name although the thing has been indicated through presumption.
Ananubhashana
(Silence)
 vijñātasya pariá¹£adā triḥ abhihitasya api apratyuccāraṇam ananubhāṣaṇamAn occasion for rebuke which arises when the opponent makes no reply to a proposition although it has been repeated three times by the disputant within the knowledge of the audience.
Ajnana
(Ignorance)
 avijñātam ca ajñānamNon-understanding of a proposition
Apratibha
(Non-ingenuity)
 uttarasya apratipattiḥ apratibhāOne’s inability to hit upon a reply
Vikshepa
(Evasion)
 kāryavyāsaṅgāt kathāvicchedaḥ viká¹£epaḥArises if one stops an argument in the pretext of going away to attend another business. 
Matanujna
(Admission of an Opinion)
 svapaká¹£e doṣābhyupagamāt parapaká¹£e doá¹£aprasaṅgaḥ matānujñāCharging the opposite side with a defect by admitting that the same defect exists in one’s own side.
Paryanuyojyopekshana
(Overlooking the censurable)
 nigrahasthānaprāptasya anigrahaḥ paryanuyojyopeká¹£aṇamNot rebuking a person who deserves rebuke. 
Niryanuyojyanuyoga
(Censuring the non-censurable)
 anigrahasthāne nigrahasthānābhiyogaḥ niranuyojyānuyogaḥRebuking a person who does not deserve rebuke
Apasiddhanta
(Deviating from a tenet)
 siddhāntam abhyupetya aniyamāt kathāprasaṅgaḥ apasiddhāntaḥAccepting a tenet and then departing from it in the course of his disputation,
Hetvabhasa
(The Semblance of a reason or fallacy)
 hetvābhāsāḥ ca yathoktāḥUsing erratic, the contradictory, the equal to the question, the unproved, and the mistimed

But, a word of caution. Charaka says debate is of two types – Anuloma Sambhasha(congenial debate) and Vigrhya Sambhasha(hostile debate). The congenial debate has the main traits of erudition, wisdom, eloquence and readiness to reply, not being wrahful or malicious, is well versed in the art of persuation and is patient and sweet speeched. Defeat and victory should be treated equally. Topic shouldn’t be diverted. On the other hand, for a hostile debate, the debater should indulge in a casual discussion to understand his opponent’s strengths and weaknesses and should focus on erudition, wisdom, memory, ingenuity and eloquence. Irritability, shallowness, shyness and inattentiveness should be avoided. He further states, ridicule, insult their knowledge and not allowing your opponent to speak should be the practice. However, such a method shouldn’t be employed against old people. Ultimately, he says, whatever the type of debate, focus on the weaknesses on your opponent and not on your strengths.
This effectively means that though a majority of the tenets hold in both the cases, you may need to revisit them based on your audience.

References:

A History of Indian Logic – Satischandra Vidyabhushana

Gautama Nyaya Sutras

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