There are three types of discussion possible, according to nyaya Shastra. They are 1. Vadha 2. Jalpa and 3. Vithanda.
Vadha – “pramaana – tarka – saadhanopalambha – siddhantaaviruddha panca-avayava-upapanna paksha-pratipaksha-parigraha vaadha” (nyaya sutra)
With the help of the means of right knowledge “pramana” and logic “tarka” following ones idea one should use the syllogory endowed with all the five terms / parts of it and prove their idea is vaadha. Here, the important thing to notice is, both the people involved in the discussion are only interested in presenting their idea to come to a conclusion, which both can accept. That is, they don’t have any fixed idea of the conclusion.
The five parts of the syllogory is pratigna, hetu, udhaarana, upanaya and nigamana. Pratigna is to present the goal or aim of the syllogory / logic, hetu is the reason we use to prove it, udhaarana is the example we use which fits in both the aim and the reasoning, upanaya is to present the idea that there is a concomitance here and nigamana is to show that the logic fits in this place.
The syllogory will look like this – the mountain has fire, because it has smoke, like the kitchen fire, where there is smoke there is fire, here it is like this.
There are different schools of logicians who say that not all the five parts is necessary. Like, the vedantins only accept the first or the last three. The Buddhist accepts only two etc.
Jalpa – “Yathokthopapanna chala-jati-nigrahasthana-saadhanopalambha jalpa” (nyaya sutra)
In this type of dialogue, one should present one’s own idea and condemn the others idea by showing the error like jaati uttara, and other nigrasthana.
One is very sure of one’s own idea, and based on it he presents the logic to prove his point and based on it or some pre-decided idea shows the error in the opponents idea.
Before entering into a dialogue both the parties decide on a common ground of discussion. Like what will one base his dialogue and what will one not base it upon, what is the time one will take to reply (we cannot take years to reply) etc. during this discussion sometimes just to fool the opponent with a semblance of logic or logic based on the semblance of the pre-decided points if one throws a point, then if it is pointed out by the other, it is called nigrahasthana.
Vithanda – “satpratipaksha-staapanaa-hiina vitanda” (nyaya sutra)
In this type of dialogue, one should only resort to condemning the others idea, without presenting one’s own idea. And it is accepted. If the person says his side of idea or if he even accepts that he is doing a vithanda he loses the position of being a vaitandika.