The Nyâya school of philosophy objects to this view and says that the capacity of anything cannot be known until the effect produced is known, and if capacity to produce effects be regarded as existence or being, then the being or existence of the effect cannot be known, until that has produced another effect and that another _ad infinitum_. Since there can be no being that has not capacity of producing effects, and as this capacity can demonstrate itself only in an infinite chain, it will be impossible to know any being or to affirm the capacity of producing effects as the definition of existence. Moreover if all things were momentary there would be no permanent perceiver to observe the change, and there being nothing fixed there could hardly be any means even of taking to any kind of inference. To this Ratnakirtti replies that capacity (_saâmarthya_) cannot be denied, for it is demonstrated even in making the denial. The observation of any concomitance in agreement in presence, or agreement in absence, does not require any permanent observer, for under certain conditions of agreement there is the knowledge of the concomitance of agreement in presence, and in other conditions there is the knowledge of the concomitance in absence. This knowledge of concomitance at the succeeding moment holds within 160 itself the experience of the conditions of the preceding moment, and this alone is what we find and not any permanent observer. The Buddhist definition of being or existence (_sattva_) is indeed capacity, and we arrived at this when it was observed that in all proved cases capacity was all that could be defined of being;--seed was but the capacity of producing shoots, and even if this capacity should require further capacity to produce effects, the fact which has been perceived still remains, viz. that the existence of seeds is nothing but the capacity of producing the shoots and thus there is no vicious infinite [Footnote ref l]. Though things are momentary, yet we could have concomitance between things only so long as their apparent forms are not different (_atadrûpaparâv@rttayoreva sâdhyasâdhanayo@h pratyak@se@na vyâptigraha@nât_). The vyâpti or concomitance of any two things (e.g. the fire and the smoke) is based on extreme similarity and not on identity.