Vācaspatiによる認識の他律的検証過程 : NVTTにおける真知論

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It is well-known that the Nyāya advocates a so-called 'extrinsic theory of truth' (paratah-prāmāņya-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 Nyāyavārttikatātparyaţīkā 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 (prāmāņya) 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 (pravŗtti-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 (prāmāņya) of this or that mantra or this or that statement of the Āyurveda by means of the fruitfulness of actions based on them. Thus one ascertains for those mantras and Āyurveda that property of being uttered or written by a reliable speaker (āptoktatva) which is invariably concomitant with the property of being true (prāmāņya). 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 (abhyāsadaśāpanna). 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 action by means of the reason 'the property of being of the same kind' as in the case of those mantras and Āyurveda in which their validity has been repeatedly verified. What specifically serves as tajjātīyatā in this case is the 'property of being uttered by a reliable speaker'(āptoktatva). In this way Vācaspati makes a clear distinction between cases which are concerned with what has not yet been experienced repeatedly and those concerned with what has already been experienced or familiar cases. In the former instance one may not apprehend the truth of a cognition until one ascertains the fruitfulness of an action afterwards, whereas in the latter instance one can make the verification in advance by means of inference from its similarity to what has been experienced again and again. Moreover, Vācaspati seems to have taken the problem of infinite regress much more seriously than Jayanta. If any cognition should need to be validated by any other confirmatory cognition whatsoever, that confirmatory cognition itself would also need to be validated by still another cognition, and this process would have no end. To avoid this difficulty of the extrinsic theory, Vācaspati explicitly accepts a certain number of cognitions or cognitive processes which are known or must be known to be true right from the beginning. Among these intrinsically valid cognitions are the apprehension of the logical reason tajjātīyatā, the awareness (samvedana) of any cognition such as 'I have obtained the cognition of water' or 'I have obtained the experience of drinking water', and instances of inference such as the deduction of the truth of K2 from the logical reason tajjātīyatā and the deduction of the truth of K1 from the truth of K2. In this connection it may be interesting to note M. Inami [1993], according to which Kamalaśīla acknowledges intrinsic truth or validity for five sorts of cognitions, which are the perceptive self-awareness of cognition (svasamvedana pratyakşam), the cognition of yogins, the ascertainment of arthakriyā, the inference, and the perception repeated many times in the past (abhyāsavat pratyakşam). At any rate, if we adopt Tanizawa's [2000a] characterization of the Nyāya extrinsic theory of truth as a type of 'foundationalism', it may safely be said that Vācaspati made a further step to strengthening its foundationalism by going so far as to make some concession to the intrinsic theory of truth (svatah-prāmāņya-vāda).
2002-09-20

著者

志田泰盛
日本学術振興会

Vācaspatiによる認識の他律的検証過程 : NVTTにおける真知論

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