Vācaspatiによる認識の他律的検証過程 : NVTTにおける真知論=Vācaspati's Theory of the Extrinsic Apprehension of the Truth of a Cognition (paratah prāmāņya) : In Comparison with Jayanta's View
It is well-known that the Nyāya advocates a so-called 'extrinsic theory of truth' (paratah-prāmā?ya-vāda), but not much study has been done on the historical development of this theory in all its details. The present paper tries to shed new light on this subject by examining the nature of Vācaspati's arguments for the extrinsic apprehension of the truth of a cognition (jñāna) in his Nyāyavārttikatātparya?īkā in comparison with Jayanta's relevant observations. The Nyāya extrinsic theory of truth, as developed by the time of Jayanta, may be divided into two aspects, i.e. the origination of truth (utpatti) and the apprehension or verification of truth (jñapti). First, it is asserted that the property of being true (prāmā?ya) or erroneous in a given cognition (K1) originates from some additional causes which are different (paratah) from the causal complexes that generate the cognition as such. Second, the truth of a cognition is not ascertained by that cognition itself (K1) or the consciousness of it, but by some other cognition (K2) (paratah), i.e. the cognition of fruitfulness of the action (prav?tti-sāmarthya) which follows upon K1. With regard to the second aspect, however, an objection is raised to the effect that if this were the case, one would have to commence an action, such as a Vedic ritual in particular requiring a large amount of money and exertion, without any certainty of its fruitfulness, and this would amount to the practical meaninglessness of the verification of truth. Against this objection Jayanta replies as follows. This objection might be true on the level of everyday life in which it would not make much difference whether one can ascertain the truth of a cognition before or after the action. But as far as the Vedic level is concerned, one must know the truth of a cognition which is obtained only by understanding Vedic scriptures in advance of leaping into a relevant ritual action, and it is nothing but the extrinsic theory of truth that makes that verification of truth possible. How is this possible? According to Jayanta, one first verifies the truth or validity (prāmā?ya) of this or that mantra or this or that statement of the ?yurveda by means of the fruitfulness of actions based on them. Thus one ascertains for those mantras and ?yurveda that property of being uttered or written by a reliable speaker (āptoktatva) which is invariably concomitant with the property of being true (prāmā?ya). Then one applies this invariable concomitance to a given statement of the Vedas, reaching the ascertainment of the truth of the Vedic message before setting about undertaking the ritual performance. In short, Jayanta classifies the issues of verification into everyday cases and Vedic cases. In his view, the truth of a cognition is extrinsically verifiable after the apprehension of a successful action based on it, though the problem of verification itself may not be very important on the level of everyday life. The real significance of the extrinsic apprehension of truth in the context of everyday life lies in the fact that it ultimately leads to the verification of such Vedic messages as are concerned with anything extraordinary which cannot be otherwise verified. Vācaspati provides a different solution. He emphasizes that it is possible to apprehend the truth of a cognition before the action so long as the cognition is concerned with what has been repeatedly experienced (abhyāsada?āpanna). It makes no difference here whether it is a matter of everyday life or of the Vedic scriptures. For example, when one drinks water after having experienced the drinking of it again and again, one's apprehension 'I drank water' is, so to say, enough to establish the truth of the cognition, since one infers the truth from the apprehension's 'property of being of the same kind' (tajjātīyatā) as the previous experiences of drinking water. Likewise, one can infer the truth of Vedic statements in an extrinsic manner before leaping into acti
