Anvaya Vyapti is a term employed in Nyaya philosophy. Vyapti literally means pervasiveness. It signifies the universal relation between the hetu (middle term) and the Sadhya (major term), the classical example being that of smoke and fire. More specifically, vyapti is defined as invariable concomitance. Concomitance refers to the co-existence of vyapya (smoke) and the vyapaka (fire) in one and the same substratum (fire place). This is not necessarily a relation of karya karanabhava (cause and effect) or identity of essence (tadatmya). The middle and major terms are not necessarily co-existent. For instance, smoke is always accompanied by fire whereas fire is not always accompanied by smoke.
Invariable concomitance is of two types
- Affirmative (anvaya vyapti) and
- Negative (vyatierka vyapti)
The former indicates ‘agreement in presence’. That is,
wherever there is vyapya (smoke) there is necessarily vyapaka (fire). On the
other hand, negative affirmation signifies ‘agreement in absence’. According to
this, the relationship is as follows – wherever there is no vyapaka (no fire),
there is no vyapya (no smoke). While Naiyayikas include both types of vyapti
under anumana (inference), certain other schools like Mimamsa and Advaaita
Vedanta, acknowledge only anvaya vyapti as a part of inference. They treat
negative affirmation as a state of postulation (arthapatti), which is another
independent means of knowledge. The inference containing anvaya vyapti alone is
called kevalanvayi (purely affirmative). The commonly found examples, however,
have both anvaya and vyatireka vyapti, as in the case of smoke and fire. Such an
inference is called anvaya vyatireki. The inference where vyatireka vyapti
alone is available, is called kevala vyatireki.