インド知識論における真・偽の問題 : 正理・勝論学派を中心として

Abstract

This article is intended for a brief account how the Nyāya-Vaiśeşikas hold about the truth value of a knowledge, as compared with the Mīmāmsakas who stand on the similar metaphysical footing, viz. positive realism. 'Truth' (prāmāņya) or 'falsity' (aprāmāņya) is a property or a truth value ascribed to a true knowledge (pramā) or an erroneous knowledge (apramā) respectively, and is to be determined as such in accordance as the cognition corresponds to the fact. In traditional Western logic, the term 'true' or 'false' has heen used to designate a proposition as is logically true or false. On the other hand, by the term 'valid' or 'invalid' is meant to denote a means of knowledge (pramāņa) as a process or operation charged with logical necessity, although both 'true' and 'validity' are expressed by a Sanskrit term 'prāmāņya'. The truth value of a knowledge can be viewed from different stand-points in Indian epistemology, that is, what elements do condition the truth value, and what makes us apprehend the knowledge or cognition as true or false. The former refers to its origination or constitution (utpatti) of the truth value, while the latter concerns its cognitive ascertainment (jñapti). In other words, the bone of contention about this problem centres around (1) the causal elements which objectively originate and constitute the truth value (janakakāraņa-vişayaka) and (2) the factors which make the cognition and its truth value intelligible to us (jñāpaka-kāraņa-vişayaka). In view of this background, Indian thinkers hold two kinds of views regarding the objective constitution and the subjective ascertainment of the truth value ; one is that the truth value, say the truth, is self-determined (svatah-prāmāņya), and the other is that it is determined by extreneous conditions (paratah-praāmāņya), each school accepting either of these alternative views in relation to the truth and the falsity. According to the theory of svatah-prāmāņya which is advocated by the Mīmāmsakas and the Advaita-vedāntins etc., any knowledge is conditioned as true by the same constituent elements of the knowledge, and the truth is also cognized by the same causes that make us apprehend the knowledge. However, when the difference of views between the said two schools taken into account, the truth only shall be here scrutinized in connection with the determination of the truth value. The Nyāya-Vaiśeşikas hold the view that mere cognition 'this is a jar' necessarily leads to an after-cognition or apperception 'I know that this is a jar' or 'I have the knowledge that this is a jar', which involves the first cognition as its content. But the cognition of the truth is an entirely different matter, which is to be inferred on the basis of practical utility ; the truth of a cognition is first cognized by us, only when we act upon the knowledge or even in the midst of doubt about it, and see the action lead to a conative satisfaction. From the fruitful of the cognition the truth is inferred, for whatever thing is not true does not give rise to 'fruitful action'. In the case of a cognition about unfamiliar object, it is purely negative form of inference based on the failure of our attempt. However, when a severe attack be made by the opponents as to how the validity of the conative satisfaction and the inference etc., can be tested as such, the later Naiyāyikas try to evade the difficulties even by accepting self-determined cognitions and means thereof. Among them are counted inference (anumāua), comparison (upamāna), cognition of resemblance between two cognitions (jñāna-gata-sādŗśya-jñāna), after-cognition (anuvyavasāya) and cognition of anything as mere subject (dharmi-jñāna).