whether by being produced by the instrumental causes _only_ which produced right knowledge, you mean to include or exclude the absence of a 'defect'? It cannot be the former alternative; because the followers of the Nyáya who hold that authoritativeness is proved by something external [as inference, &c.], would at once grant that authoritativeness is produced by the instrumental causes of knowledge combined with the absence of a 'defect.' Neither can it be the latter alternative; for, inasmuch as it is certain that the absence of a 'defect' is found combined with the various instrumental causes, this absence of a 'defect' is fixed as by adamantine glue to be a cause of right knowledge, since right knowledge will always accompany its presence, and be absent if it is absent,[290] and it will at the same time be not an unimportant condition.[291] If you object that non-existence (or absence) cannot be a cause, we reply by asking you whether non-existence can be an effect or not? If it cannot, then we should have to allow that cloth is eternal, as its "emergent non-existence" or destruction would be impossible. If it can be an effect, then why should it not be a cause also? So this rope binds you at both ends. This has also been said by Udayana [in his Kusumáñjali, i. 10]-- "'As existence, so too non-existence is held to be a cause as well as an effect.' "The argument, in my opinion, runs as follows:--Right knowledge depends on some cause[292] other than the common causes of knowledge, from the very fact that, while it is an effect, it is also knowledge, just as wrong knowledge does.[293] Authoritativeness is known through something external to itself [_e.g._, inference], because doubt arises in regard to it in an unfamiliar case, as we also see in non-authoritativeness. "Therefore, as we can prove that authoritativeness is both produced and recognised by means of something external, the Mímáṃsá tenet that 'authoritativeness is self-proved' is like a gourd overripe and rotten."