[Footnote 1: Kâryyakâra@nubhâvâdvâ svabhâvâdva niyâmakât avinâbhâvaniyamo' dars'anânna na dars'anât. Tâtparya@tîkâ, p. 105.]
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immediate succession the effect disappears. But this method cannot guarantee the infallibility of the determination of cause and effect relation; and if by the assumption of a cause-effect relation no higher degree of certainty is available, it is better to accept a natural relation without limiting it to a cause-effect relation [Footnote ref 1].
In early Nyâya books three kinds of inference are described, namely pûrvavat, s'e@savat, and sâmânyato-d@r@s@ta. Pûrvavat is the inference of effects from causes, e.g. that of impending rain from heavy dark clouds; s'e@savat is the inference of causes from effects, e.g. that of rain from the rise of water in the river; sâmânyato-d@r@s@ta refers to the inference in all cases other than those of cause and effect, e.g. the inference of the sour taste of the tamarind from its form and colour. Nyâyamañjarî mentions another form of anumâna, namely paris'e@samâna (reductio ad absurdum), which consists in asserting anything (e.g. consciousness) of any other thing (e.g. âtman), because it was already definitely found out that consciousness was not produced in any other part of man. Since consciousness could not belong to anything else, it must belong to soul of necessity. In spite of these variant forms they are all however of one kind, namely that of the inference of the probandum (sâdhya) by virtue of the unconditional and invariable concomitance of the hetu, called the vyâpti-niyama. In the new school of Nyâya (Navya-Nyâya) a formal distinction of three kinds of inference occupies an important place, namely anvayavyatireki, kevalânvayi, and kevalavyatireki. Anvayavyatireki is that inference where the vyâpti has been observed by a combination of a large number of instances of agreement in presence and agreement in absence, as in the case of the concomitance of smoke and fire (wherever there is smoke there is fire (anvaya), and where there is no fire, there is no smoke (vyatireka)). An inference could be for one's own self (svârthânumâna) or for the sake of convincing others (parârthânumâna). In the latter case, when it was necessary that an inference should be put explicitly in an unambiguous manner, live propositions (avayavas) were regarded as necessary, namely pratijña (e.g. the hill is fiery), hetu (since it has smoke), udâhara@na (where there is smoke there is fire, as in the kitchen), upanaya (this hill has smoke), niga@mana (therefore it has got
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[Footnote 1: Vâtsyâya@na's bhâsya, Udyotakara's Vârttika and Tâtparyya@tîkâ, I.i. 5.]
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fire). Kevalânvayi is that type of inference, the vyâpti of which could not be based on any negative instance, as in the case "this object has a name, since it is an object of knowledge (ida@m, vâcyam prameyatvât)." Now no such case is known which is not an object of knowledge; we cannot therefore know of any case where there was no object of knowledge (prameyatva) and no name (vâcyatva); the vyâpti here has therefore to be based necessarily on cases of agreement—wherever there is prameyatva or an object of knowledge, there is vâcyatva or name. The third form of kevalavyatireki is that where positive instances in agreement cannot be found, such as in the case of the inference that earth differs from other elements in possessing the specific quality of smell, since all that does not differ from other elements is not earth, such as water; here it is evident that there cannot be any positive instance of agreement and the concomitance has to be taken from negative instances. There is only one instance, which is exactly the proposition of our inference—earth differs from other elements, since it has the special qualities of earth. This inference could be of use only in those cases where we had to infer anything by reason of such special traits of it as was possessed by it and it alone.
Upamâna and S'abda.
The third pramâ@na, which is admitted by Nyâya and not by Vais'e@sika, is upamâna, and consists in associating a thing unknown before with its name by virtue of its similarity with some other known thing. Thus a man of the city who has never seen a wild ox (gavaya) goes to the forest, asks a forester—"what is gavaya?" and the forester replies—"oh, you do not know it, it is just like a cow"; after hearing this from the forester he travels on, and on seeing a gavaya and finding it to be similar to a cow he forms the opinion that this is a gavaya. This knowing an hitherto unknown thing by virtue of its similarity to a known thing is called upamâna. If some forester had pointed out a gavaya to a man of the city and had told him that it was called a gavaya, then also the man would have known the animal by the name gavaya, but then this would have been due to testimony (_s'abda-prama@na). The knowledge is said to be generated by the upamâna process when the association of the unknown animal with its name is made by the observer