The Nyaya-Vais'e@sika in most of its speculations took that view of things which finds expression in our language, and which we tacitly assume as true in all our ordinary experience. Thusthey admitted dravya, gu@na, karma and samanya, Vis'e@sa they had to admit as the ultimate peculiarities of atoms, for they did not admit that things were continually changing their qualities, and that everything could be produced out of everything by a change of the collocation or arrangement of the constituting atoms. In the production of the effect too they did not admit that the effect was potentially pre-existent in the cause. They held that the material cause (e.g. clay) had some power within it, and the accessory and other instrumental causes (such as the stick, the wheel etc.) had other powers; the collocation of these two destroyed the cause, and produced the effect which was not existent before but was newly produced. This is what is called the doctrine of _asatkaryavada_. This is just the opposite of the Sa@mkhya axiom, that what is existent cannot be destroyed _nabhavo vidyate sata@h_) and that the non-existent could never be produced (_nasato vidyate bhavah_). The objection to this view is that if what is non-existent is produced, then even such impossible things as the hare's horn could also be produced. The Nyaya-Vais'e@sika answer is that the view is not that anything that is non-existent can be produced, but that which is produced was non-existent [Footnote ref 476].
It is held by Mima@msa that an unseen power resides in the cause which produces the effect. To this Nyaya objects that this is neither a matter of observation nor of legitimate hypothesis, for there is no reason to suppose that there is any transcendental operation in causal movement as this can be satisfactorily explained by molecular movement (_parispanda_). There is nothing except the invariable time relation (antecedence and sequence) between the cause and the effect, but the mere invariableness of an antecedent does not suffice to make it the cause of what succeeds; it must be an unconditional antecedent as well (_anyathasiddhis'unyasya niyatapurvavarttita_). Unconditionality and invariability are indispensable for _karyakara@na-bhava_ or cause and effect relation. For example, the non-essential or adventitious accompaniments of an invariable antecedent may also be invariable antecedents; but they are not unconditional, only collateral or indirect. In other words their antecedence is conditional upon something else (_na svatantrye@na_). The potter's stick is an unconditional invariable antecedent of the jar; but the colourof a stick or its texture or size, or any other accompaniment or accident which does not contribute to the work done, is not an unconditional antecedent, and must not therefore be regarded as a cause. Similarly the co-effects of the invariable antecedents or what enters into the production of their co-effects may themselves be invariable antecedents; but they are not unconditional, being themselves conditioned by those of the antecedents of which they are effects. For example, the sound produced by the stick or by the potter's wheel invariably precedes the jar but it is a co-effect; and akas'a (ether) as the substrate and vayu (air) as the vehicle of the sound enter into the production of this co-effect, but these are no unconditional antecedents, and must therefore be rejected in an enumeration of conditions or causes of the jar. The conditions of the conditions should also be rejected; the invariable antecedent of the potter (who is an invariable antecedent of the jar), the potter's father, does not stand in a causal relation to the potter's handiwork. In fact the antecedence must not only be unconditionally invariable, but must also be immediate. Finally all seemingly invariable antecedents which may be dispensed with or left out are not unconditional and cannot therefore be regarded as causal conditions. Thus Dr. Seal in describing it rightly remarks, "In the end, the discrimination of what is necessary to complete the sum of causes from what is dependent, collateral, secondary, superfluous, or inert (i.e. of the relevant from the irrelevant factors), must depend on the test of expenditure of energy. This test the Nyaya would accept only in the sense of an operation analysable into molar or molecular motion (_parispanda eva bhautiko vyapara@h karotyartha@h atindriyastu vyaparo nasti._ Jayanta's Manjari Ahnika I), but would emphatically reject, if it is advanced in support of the notion of a mysterious causal power or efficiency (_s'akti_) [Footnote ref 477]." With Nyaya all energy is necessarily kinetic. This is a peculiarity of Nyaya--its insisting that the effect is only the sum or resultant of the operations of the different causal conditions--that these operations are of the nature of motion or kinetic, in other words it firmly holds to the view that causation is a case of expenditure of energy, i.e. a redistribution of motion, but at the same time absolutely repudiates the Sa@mkhya conception of power or productiveefficiency as metaphysical or transcendental (_atindriya_) and finds nothing in the cause other than unconditional invariable complements of operative conditions (_kara@na-samagri_), and nothing in the effect other than the consequent phenomenon which results from the joint operations of the antecedent conditions [Footnote ref 478]. Certain general conditions such as relative space (_dik_), time (_kala_), the will of Is'vara, destiny (_ad@r@s@ta_) are regarded as the common cause of all effects (_karyatva-prayojaka_). Those are called _sadhara@na-kara@na_ (common cause) as distinguished from the specific causes which determine the specific effects which are called _sadhara@na kara@na_. It may not be out of place here to notice that Nyaya while repudiating transcendental power (_s'akti_) in the mechanism of nature and natural causation, does not deny the existence of metaphysical conditions like merit (_dharma_), which constitutes a system of moral ends that fulfil themselves through the mechanical systems and order of nature.
The causal relation then like the relation of genus to species, is a natural relation of concomitance, which can be ascertained only by the uniform and uninterrupted experience of agreement in presence and agreement in absence, and not by a deduction from a certain _a priori_ principle like that of causality or identity of essence [Footnote ref 479].
The material cause such as the clay is technically called the _samavayi-kara@na_ of the jug. _Samavaya_ means as we have seen an intimate, inseparable relation of inherence. A kara@na is called _samavayi_ when its materials are found inseparably connected with the materials of the effect. Asamavayi-kara@na is that which produces its characteristics in the effect through the medium of the samavayi or material cause, e.g. the clay is not the cause of the colour of the jug but the colour of the clay is the cause of the colour of the jug. The colour of the clay which exists in the clay in inseparable relation is the cause of the colour of the jug. This colour of the clay is thus called the asamavayi cause of the jug. Any quality (_gu@na_) or movement which existing in the samavaya cause in the samavaya relation determines the characteristics of the effect is called the asamavayi-kara@na. The instrumental_nimitta_ and accessory (_sahakari_) causes are those which help the material cause to produce the effect. Thus the potter, the wheel and the stick may be regarded as the nimitta and the sahakari causes of the effect.
We know that the Nyaya-Vais'e@sika regards the effect as nonexistent, before the operation of the cause in producing it, but it holds that the gu@nas in the cause are the causes of the gu@nas in the effect, e.g. the black colour of the clay is the cause of the black colour of the effect, except in cases where heat comes as an extraneous cause to generate other qualities; thus when a clay jug is burnt, on account of the heat we get red colour, though the colour of the original clay and the jug was black. Another important exception is to be found in the case of the production of the parima@nas of dvya@nukas and trasare@nus which are not produced by the parima@nas of an a@nu or a dya@nuka, but by their number as we have already seen.