Nyāya Sūtras 38

Or, through its contrary, it is the opposite.

"An instance is an example" is the subject under discussion. An example is an instance which, through dissimilarity to what is to be proved, does not possess its property. [For instance:] "Sound is non-eternal, because it has the property of having an origin; that which does not have the property of having an origin is eternal, such as the self." This instance, such as the self, through dissimilarity to what is to be proved, namely through not having the property of having an origin, does not possess its property—that property of what is to be proved, namely non-eternality, does not exist in it.

Apprehending here in the instance, such as the self, that non-eternality does not exist because of the absence of the property of having an origin, one infers the contrary in sound: sound is non-eternal because of the presence of the property of having an origin. In the case of a logical reason stated through similarity, the example is an instance which possesses its property through similarity to what is to be proved. In the case of a logical reason stated through dissimilarity, the example is an instance which does not possess its property through dissimilarity to what is to be proved.

In the former instance, whichever two properties one sees standing as what is to be proved and what proves, one infers their relation of what is to be proved and what proves in the subject to be proved as well. In the latter instance, one sees the absence of the other from the absence of one of the two properties, and infers in the subject to be proved the presence of the other from the presence of one of them. Because this does not obtain in pseudo-reasons, pseudo-reasons are non-reasons.

This efficacy of the logical reason and the example is extremely subtle, difficult to comprehend, and to be understood only by the learned.