In Tarkasamgraha, the Nyaya school advocates for Paratah Pramanyavada, which means the validity (Pramanya) of knowledge is both originated and known extrinsically.
"Validity is not self-evident. It is known by successful outcome of actions based on that knowledge."
This contrasts with the Svatah Pramanyavada of the Mimamsa school, which believes knowledge is self-validating.
The Nyaya-Vaisesika school explains the psychological process of error through the theory of Anyathakhyati.
Error occurs when one object is perceived as something else ("Anyatha").
Hetvabhasa literally means "that which appears as a reason but is not a valid reason". A valid inference depends on a flawless Hetu (middle term). If the Hetu is defective, the inference becomes a fallacy.
| Type | Name | Definition |
|---|---|---|
| Savyabhichara | Irregular Middle | The reason is not uniformly related to the major term (e.g., "Sound is eternal because it is an object of knowledge"). |
| Viruddha | Contradictory Middle | The reason actually disproves the very thing it is supposed to prove (e.g., "Sound is eternal because it is produced"). |
| Satpratipaksa | Inferentially Contradicted | When there is another reason of equal strength that proves the opposite. |
| Asiddha | Unproved Middle | The reason itself is not a proven fact or is not present in the subject (e.g., "Sky-lotus is fragrant because it is a lotus"). |
| Badhita | Non-inferentially Contradicted | The conclusion is contradicted by a stronger Pramana like perception (e.g., "Fire is cold because it is a substance"). |
Q: Why is Savyabhichara also called 'Inconstant'?
A: Because the reason leads to both the presence and the absence of the major term, creating no certainty.
Q: What is the main difference between Badhita and Satpratipaksa?
A: In Badhita, the conclusion is disproved by perception or another source. In Satpratipaksa, it is countered by another equally strong inference.