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b. When X is absent, Y is absent. (2) a. When X occurs, Y is absent.
b. When X is absent, Y occurs. If (1a, b) hold in all instances for X and Y, so that these are shown consistently to occur together, one is entitled to say that a particular relation obtains between the two. Either (1a) or (1b) alone will not justify this, and a claim made on the basis of either can be falsified by showing that (2a) or (2b) holds. One relation that can be established by (1) is that X is a cause of Y. A special instance of the cause-effect relation involves the use of given speech units and the understanding by a hearer of given meanings. If (1a, b) hold, the speech unit in question is considered the cause of one's comprehending a meaning, which is attributed to that speech element.
Cardona named anvaya and vyatireka the 'Indian Principle of Inductive Reasoning' and considered them to be the means for discovering a certain relationship between two items, such as a causal relation between a fire and smoke and a relation between a word and its meaning.
In the case of the trairūpya theory, anvaya and vyatireka establish the relation between sādhya and sadhana / lingin and linga / gamya and gamaka; in short, anvaya and uyatireka together are a kind of the inductive method by which we can determine what is a valid inferential mark. In other words, the second and the third characteristics without the particle eva express the necessary conditions for a valid inferential mark.
2. 2. 2. The trairūpya formulae with eva and the meaning of the eva
restriction In PS-Vștti II. 5cd, as I have shown above, Dignāga inserts the restrictive particle eva at least in the second characteristic of a valid inferential mark in the following manner:
(6) tattulye eva [lingasya] sadbhāvaḥ /
