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4. Conlcusion
In PS II Dignaga presents two different formulae of the trairūpya, one without eva and the other with eva. PS II. 5cd can be divided into the following three formulae:
(1) anumeye [lingasya] sadbhavaḥ/
(2) tat (=anumeya)-tulye [lingasya] sadbhavaḥ/
(3) [anumeya / tattulya-] asati [lingasya] nästitä/
They correspond to the following traditional formulae:
(1) [hetoh] paksadharmatvam/
(2) sapakse [hetoḥ] sattvam/
(3) vipakṣe [hetoḥ] asattvam/
The second and the third formulae are respectively called anvaya and vyatireka, which constitute what Cardona called the 'Indian Principle of Inductive Reasoning'. If we understand tattulya / sapakṣa and asat / vipaksa in the above formulae in the sense of 'the domain of presence of the property to be proven' and 'the domain of absence of the property to be proven', then anvaya and vyatireka can be reformulated in the following manner:
(1) anvaya (continued presence): in the domain of presence of the property to be proven (sadhyadharma) linga is present; e.g., where there is a
fire there is smoke.
(2) vyatireka (continued absence): in the domain of absence of the property to be proven linga is absent; e.g., where there is no fire there is no smoke.
anvaya and vyatireka constitue the inductive method or process by which we can determine what is a valid inferential mark or reason, and sapakşa and vipaksa make up what Hayes called the 'induction domain' where we can conduct such an induction. In modern terminology, anvaya and vyatireka without eva express the necessary conditions for a valid reason.
