According to Classical Indian School of Logic (Nyāya) which of the following conditions must be fullfilled by a true middle term (hetu)?

(A) It must be found in minor term (pakṣa).

(B) It must be found in all similar instances.

(C) It should not be found anywhere where major term (sādhya) is absent.

(D) The minor term in which it is said to exist should not be impossible.

Choose the most appropriate answer from the options given below:

Gautama wrote Nyaya-sutras in the second century BCE. 

Key Points

• According to Nyaya, four means of valid knowledge are admitted: perception, inference, comparison, and verbal testimony. 
• Hetu is the equivalent of the middle term.
• It also goes by the names "linga," "mark," and "sign."
• For example, ​
  • Major Premise: All things which have smoke have a fire.
  • Minor Premise: This hill has smoke
  • Conclusion: Therefore, this hill has a fire.
• Here ‘smoke’ is the middle term, ‘hill’ is the minor term and  ‘fire’ is the major term.
• It is discovered twice, first in relation to sdhya and subsequently to paksa.
• Finally, it aids in the establishment of sdhya in paksa.
• Smoke is referred to as "hetu" on the inference made above. 

Therefore, the most appropriate answer from the options (A), (B), (C), (D) only.

Additional Information

• Any anumna (inference) must have a "vypti" relationship between Hetu and Sdhya.
• An invariable, unconditional, and the universal relationship between the major term and the middle term of an inferential argument is known as vypti.